Abstract
The objective of the present study was to consider the regulatory role of exogenous nitric oxide (NO) supplementation in response to chilling stress impose alterations on different physiological parameters in melon seedlings. Melon seedlings were treated with sodium nitroprusside (SNP, an NO donor), hemoglobin (a NO scavenger), NG-nitro-L-arginine methyl ester (an NO synthase inhibitor), and tungstate (a nitrite reductase inhibitor) under chilling stress conditions. The results showed that exogenous SNP improves the growth of melon seedlings under chilling stress conditions and ameliorates the harmful effects of chilling stress by increasing the levels of chlorophyll and soluble solutes, elevating the activity of sucrose phosphate synthase by enhancing the expression level of CmSPS. Moreover, exogenous NO significantly enhances the expression of genes and activities of antioxidant enzymes under chilling stress, resulting in lower reactive oxygen species accumulation. However, the protective effects of SNP are reversed by both NO scavenging and inhibition. Collectively, our results reveal that NO has the ability to ameliorate the harmful effects of chilling stress on melon seedlings by regulating carbohydrate metabolism and the antioxidant defense system.
As an economically important crop, melon (Cucumis melo L.) is extensively cultivated in temperate and tropical regions and is highly sensitive to low-temperature conditions (RodrÃguez-López et al., 2000). Chilling stress at the early cultivation stages causes seedling injury, resulting in prolonged seedling stage and delaying fruit harvest (Paull, 1990). Low temperature seriously limits crop growth, yields, and quality (Zhang et al., 2021). Low temperatures can cause increased cell membrane permeability, reactive oxygen species (ROS) accumulation, and membrane lipid peroxidation (Ding et al., 2020). In addition, low temperatures could disrupt photosynthesis (Ruelland et al., 2009). Plants have evolved a series of strategies to cope with low-temperature stress, such as strengthening the induction of antioxidant systems and the synthesis of protective molecules (sugar, proline, and polyamines) (Theocharis et al., 2012).
Nitric oxide (NO) is a free-radical molecule that is involved in plant responses to adverse environmental conditions, such as salt, water, heat, chilling, ultraviolet B, and heavy metal stresses (Fancy et al., 2017; Sharma et al., 2020). NO can act as an antioxidant to scavenge excessive ROS and activates the gene expression of antioxidant enzymes (Simontacchi et al., 2013), NO can also modulate stress tolerance by interacting with phytohormones, such as abscisic acid (ABA), auxin, and cytokinin (Tossi et al., 2009; Wasternack et al., 2006; Xu et al., 2010). NO treatment can increase freezing tolerance by upregulating the expression of CmCBF1 and CmCBF3 in Hami melon fruit (Zhang et al., 2017). Moreover, NO could regulate the expression of genes and metabolites involved in nitrogen metabolism to protect tall fescue against Cd stress (Zhu et al., 2020). Transcriptome analysis revealed that many NO-responsive genes contribute to defense stress responses (Zeng et al., 2014).
As the primary product of photosynthesis, carbohydrates, especially soluble sugars (sucrose, glucose, and fructose), can function as nutrients, osmolytes, or signaling molecules in response to abiotic stresses (Kumar et al., 2017; Ruelland et al., 2009). In the cytoplasm, sucrose phosphate synthase (SPS; EC 2.4.1.14) catalyzes sucrose synthesis (SS; Huber and Huber, 1991), while the main enzymes responsible for sucrose degradation are SS (EC 2.4.1.13) and invertase (EC 3.2.1.26) (Ranwala and Miller, 2010). In addition, SS can reversibly synthesize and degrade sucrose, with the latter being its main role (Geigenberger and Stitt, 1993). Many environmental stresses, such as cold, drought, salinity, and Ca(NO3)2, lead to significant alternations in carbohydrate metabolism (Kaur et al., 2003; Liu et al., 2004; Rosa et al., 2004; Xing et al., 2015), and it has been demonstrated that under stress conditions, soluble sugars can act as osmoprotectants that help alleviate the negative effects of stress on plants (Hu et al., 2012). Exogenous sucrose can alleviate the detrimental effects of heat stress on potato seedlings by enhancing the antioxidant enzyme system and increasing sucrose and proline accumulation (Gong and Chen, 2021). Sucrose treatment can enhance Malus halliana tolerance to Fe deficiency stress by regulating chlorophyll biosynthesis (Guo et al., 2020). Exogenous sucrose was found to differentially regulate genes involved in polyamine synthesis, which could play adaptive roles in response to atrazine stress in Arabidopsis thaliana (Amrani et al., 2019).
In view of the beneficial effects of NO on different crops under various stresses, it is reasonable to hypothesize that NO may have a regulatory effect on carbohydrate metabolism in plants under chilling stress. However, this has not been previously investigated. Accordingly, in this study, the effects of exogenous NO on plant growth, chlorophyll content, antioxidant response, and carbohydrate metabolism in melon seedlings were investigated. Thus, the current study may help further our mechanistic understanding of NO-mediated tolerance to chilling stress in plants.
Materials and Methods
Plant materials and treatment condition.
Melon seeds XL-1 were produced by our laboratory at Shanghai Academy of Agricultural Science, Shanghai, China, and germinated in incubator at 30 °C. The plants were grown at 30/20 °C (day/night) with a 12-h photoperiod, a light irradiance of 400 μM·m−2·s−1, and a relative humidity of 60% to 70%. At the three-leaf stage, the melon seedlings were sprayed with 200 mL of either distilled water (as control), 200 μM SNP (a NO donor), 0.1% hemoglobin (Hb, a scavenger of NO), 200 μM NG-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NOS), or 200 μM sodium tungstate [a nitrite reductase (NR) inhibitor] for 7 d, and then half of the seedlings in each treatment were cultured at 25/15 °C (day/night), the other half of seedlings were exposed to 15/6 °C (day/night),light irradiation of 400 μM·m−2·s−1 for 4 d. The third fully expanded leaves were sampled for each treatment. Sampling for physiological, biochemical, and molecular analysis was performed at 4 d after treatment. The leaf samples were frozen in liquid nitrogen and stored at –80 °C for further analysis.
Determination of chlorophyll content.
NO content and NR activity.
NO content was measured by the method of Diao et al. (2016). Briefly, 0.5 g of sample was placed in 100 U of catalase (CAT) and 100 U of superoxide dismutase (SOD) for 5 min to remove endogenous ROS before adding 10 mL of 5 mm oxyhemoglobin (HbO2). After incubation, NO was determined from the conversion of HbO2 to methemoglobin (metHb).
NR activity was measured as described by Diao et al. (2016). Briefly, 0.5 g of leaves were ground with 100 mm HEPES buffer [pH 7.5, 5 mm dithiothreitol, 1 mm ethylenediaminetetraacetic acid (EDTA), 10% glycerol, 0.1% Triton X-100, 0.5 mm phenylmethylsulfonyl fluoride, 1 µM leupeptin, 20 µM flavin adenine dinucleotide, 5 µM Na2MoO4, and 1% polyvinyl polypyrrolidone (PVPP)]. The homogenates were then centrifuged at 4 °C, 10,000 gn, for 20 min, and the resulting supernatants were used for NR analysis.
Sucrose content.
Sucrose was extracted using 0.5 g samples with 4 mL of 80% (v/v) ethanol for 30 min heated in a water bath at 80 °C under agitation, and the resultant mixture was centrifuged at 4000 gn for 3 min. This process was repeated three times. The supernatant was collected and used for determination of sucrose content by a modified phenol-sulfuric acid method according to Buysse and Merckx (1993).
Sucrose-metabolizing enzyme activities.
SPS and SS were determined by the method of Rufty and Huber (1983). In brief, 0.5 g of leaves were homogenized with 5 mL HEPES NaOH buffer (pH 7.5) and centrifuged at 12,000 gn for 10 min at 4 °C. The supernatant was collected for measurement of enzyme activities. The reaction mixture contained 50 μL HEPES-NaOH (pH 7.5), 20 μL 50 mm MgCl2, 20 μL 100 mm UDP-glucose, 20 μL 100 mm fructose-6-phosphate, and 50 μL of crude enzyme extract. The absorbance was measured at 485 nm. SS activity was determined in a similar way except fructose was substituted with fructose 6-phosphate.
The activities of soluble acid invertase (AI) and neutral invertase (NI) were measured by the method of Schaffer et al. (1987) with some modifications. Briefly, 0.5-g leaf samples were homogenized in liquid nitrogen, mixed with 4 mL buffer solution (200 mm potassium phosphate, pH 7.5) containing 0.1% β-mercaptoethanol, 5 mm MgCl2, 0.05% bovine serum albumin, 0.05% Triton-X100, and 2% PVPP. After incubating at 4 °C for 20 min, the mixture was centrifuged at 12,000 gn for 30 min at 4 °C. The supernatant fraction was then 80% saturated with (NH4)2SO4, allowed to stand for 30 min, and centrifuged at 12,000 gn for 20 min at 4 °C. The supernatant was discarded and desalted buffer solution (200 mm potassium phosphate, pH 7.5) was added. The enzyme extract was used to determine enzyme activity.
Soluble solute contents.
The soluble sugar content was determined by the method of Dey (1990). Soluble protein content was determined by the method of Bradford (1976). Proline contents were measured by the method of Bates et al. (1973).
Antioxidant enzyme activities.
Leaf samples (0.5 g) were homogenized with 5 ml of 50 mm potassium phosphate buffer (pH 7.0), containing 0.2 mm EDTA and 2% (w/v) PVPP. The homogenate was centrifuged at 12,000 gn for 20 min at 4 °C. The supernatant was used to measure enzyme activities.
SOD activity was determined by measuring its ability to inhibit the photochemical reduction of nitro blue tetrazolium (NBT) following the method of Giannopolitis and Ries (1977). Peroxidase (POD) activity was measured by the method of Thomas et al. (1981). The absorbance of the solution was measured at 470 nm. CAT activity was determined by the method of Cakmak and Marschner (1992). The absorbance was measured at 240 nm. For ascorbate peroxidase (APX) activity was measured according to the method of Nakano and Asada (1981). The absorbance was measured at 240 nm.
Hydrogen peroxide content, malondialdehyde content, and O2– production.
H2O2 content was determined based on the method of Patterson et al. (1984). Leaf samples (0.5 g) were homogenized with ice-cold acetone, centrifuged at 3000 gn for 20 min at 4 °C. Titanium reagent (20% titanium tetrachloride in concentrated HCl), 0.2 ml, 17 M ammonia solution was added to extract the supernatant, and centrifuged at 4 °C, 3000 gn, for 10 min, the supernatant was discarded. The pellet was washed three times with ice-cold acetone, then drained and dissolved in 3 mL of 1 mm H2SO4. The absorbance of the solution was measured at 410 nm, which was compared with standard curve plotted with pure H2O2.
The O2– production rate was measured by the method of Elstner and Heupel (1976). Leaf sample (0.5 g) was homogenized in 65 mm phosphate buffer (pH 7.8) and centrifuged at 4 °C, 6000 gn for 15 min. the supernatant were mixed with 65 mm phosphate buffer, 10 mm hydroxylamine hydrochloride, after incubation for 20 min at 25 °C, the absorbance was measured at 530 nm.
Malondialdehyde (MDA) content was determined according to a method described previously (Dhindsa et al., 1981). Next, 0.5 g leaves were homogenized in 5 mL of 10% trichloroacetic acid and then centrifuged at 12,000 gn for 20 min. The supernatant was mixed with the 2 mL, 0.6% thiobarbituric acid; the mixture was heated in a boiling water bath for 30 min and then cooled immediately. Absorbance at 450, 532, and 600 nm was read after centrifugation at 3000 gn for 10 min. MDA content was calculated based on the following formula) MDA (μM) = [6.45(A532 – A600) –0.56A450].
RNA extraction and gene expression analysis.
Total RNA was extracted from melon leaves using a Vana RNA Isolation Kit according to the manufacturer’s specifications. The yield of RNA was determined using a NanoDrop 2000 spectrophotometer (Thermo Scientific, Waltham, MA), and the integrity was evaluated using agarose gel electrophoresis with ethidium bromide staining. Real-time polymerase chain reaction (PCR) was performed using a LightCycler 480 II real-time PCR Instrument (Roche, Basel, Switzerland). Each sample was analyzed in triplicate. At the end of the PCR cycling, melting curve analysis was performed to validate the specific generation of the expected PCR product. The primer sequences were designed in the laboratory and synthesized by Generay Biotech (Generay, Shanghai, China) based on the mRNA sequences obtained from the NCBI database (Table 1). The expression levels of mRNAs were normalized to Glyceraldehyde-3-phosphate (GAPDH) and calculated using the 2-ΔΔCt method.
Accession numbers and primer sequences of the genes analyzed in this study.
Statistical analysis.
Two independent experiments were performed with three replicates in each treatment. Data were statistically analyzed by using Duncan’s multiple range test at the 0.05 level of significance. The charts were prepared using Origin 8.0.
Results
Effects of SNP on the growth of melon seedlings under chilling stress.
As shown in Table 2, the growth of melon seedlings was significantly reduced under chilling treatment. Compared with the control, plant height, stem thickness, and fresh weight were decreased by 15.54%, 11.06%, and 20.01%, respectively. Exogenous application of SNP alleviated the harmfulness of chilling-induced stress. SNP treatment under chilling stress increased plant height, stem thickness, and fresh weight by 6.35%, 9.60%, and 5.51%, respectively, as compared with single chilling stress. However, in the presence of NO scavengers and inhibitors, the SNP-mediated effects were decreased. The plant height decreased by 6.65%, 4.24%, and 7.14% treated with Hb (NO scavenger), L-NAME (NOS inhibitor), and tungstate (NR inhibitor) compared with those under chilling stress alone. There were no significant differences in these parameters among all treatments under control condition.
Effects of exogenous nitric oxide on the plant height, stem thickness, and fresh weight of melon plants under chilling stress.
Effects of SNP on the chlorophyll content of melon leaves under chilling stress.
Compared with the control, decreased Chl contents were observed in chilling-stressed melon seedlings. Exogenous SNP application improved the Chl a, Chl b, and Car contents by 40.00%, 69.57%, and 35.00% under chilling stress conditions, compared with the chilling treatment alone. However, the increases in chlorophyll contents were suppressed by scavengers or inhibitors of NO. Hb treatment significantly decreased the Chl a, Chl b, Car, and total Chl contents by 16.67%, 20.51%, 29.63%, and 17.21%, respectively, compared with SNP treatment alone. There was also no significant difference in Chl contents among all treatments under control treatment (Supplemental Table 1). Thus, the results show that exogenous SNP improves the chlorophyll contents of melon seedlings. However, the scavenging and inhibition of NO have an adverse effect on Chl contents under chilling stress.
Effects of SNP on NO production in melon leaves under chilling stress.
There were no obvious differences in NO content and NR activity among all the treatments under control condition. Relative to the control, the NO content and NR activity in melon leaves significantly increased by 58.84% and 87.67% after chilling stress treatment, respectively. Compare with the chilling stress alone, the NO content and NR activity were both further increased by SNP treatment. Application of Hb, L-NAME, and tungstate result in decreased in NO content and NR activity by 50.51% and 42.20%, 51.94% and 31.54%, and 51.84% and 40.80% compared with that for SNP treatment, respectively (Supplemental Fig. 1). In this experiment, the two inhibitors both abolished the effect of SNP on the NO content (Supplemental Fig. 1). Therefore, we speculate that the NO production through both the NOS-like and NR pathways in melon leaves under chilling stress.
Effects of SNP on the sucrose contents of melon leaves under chilling stress.
As the main product of photosynthesis, sucrose is involved in plant growth, development, and stress response. It is considered a pivotal sugar in plant life (Salerno and Curatti, 2003). The present study shows that the content of sucrose elevated by 1.67-fold in melon leaves exposed to chilling stress. Furthermore, compared with chilling stress alone, the sucrose contents for SNP treatment are increased 2.41-fold. Moreover, exogenous applications of Hb, L-NAME, and tungstate decrease the contents of sucrose. There were no obvious differences in sucrose content among all the treatments under control condition (Fig. 1).
Effect of exogenous nitric oxide (NO) on the sucrose contents of melon seedlings under chilling-stress conditions. The whole leaves of melon seedlings (three leaf stage) were sprayed with 200 mL of distilled water (as control), 200 μM sodium nitroprusside (SNP, an NO donor), 0.1% hemoglobin (Hb, a scavenger of NO), 200 μM NG-nitro-L-arginine methyl ester [L-NAME, a nitric oxide synthase (NOS) inhibitor], or 200 μM tungstate [(a nitrite reductase (NR) inhibitor] for 7 d, and then half of the seedlings in each treatment were cultured at 25 °C, and the other half of seedlings were exposed to 15 /6 °C (day/night) for 4 d. Data are expressed as mean ± standard error; n = 3. Different letters denote significant differences at P ≤ 0.05 according to Duncan’s multiple range tests.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the sucrose contents of melon seedlings under chilling-stress conditions. The whole leaves of melon seedlings (three leaf stage) were sprayed with 200 mL of distilled water (as control), 200 μM sodium nitroprusside (SNP, an NO donor), 0.1% hemoglobin (Hb, a scavenger of NO), 200 μM NG-nitro-L-arginine methyl ester [L-NAME, a nitric oxide synthase (NOS) inhibitor], or 200 μM tungstate [(a nitrite reductase (NR) inhibitor] for 7 d, and then half of the seedlings in each treatment were cultured at 25 °C, and the other half of seedlings were exposed to 15 /6 °C (day/night) for 4 d. Data are expressed as mean ± standard error; n = 3. Different letters denote significant differences at P ≤ 0.05 according to Duncan’s multiple range tests.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the sucrose contents of melon seedlings under chilling-stress conditions. The whole leaves of melon seedlings (three leaf stage) were sprayed with 200 mL of distilled water (as control), 200 μM sodium nitroprusside (SNP, an NO donor), 0.1% hemoglobin (Hb, a scavenger of NO), 200 μM NG-nitro-L-arginine methyl ester [L-NAME, a nitric oxide synthase (NOS) inhibitor], or 200 μM tungstate [(a nitrite reductase (NR) inhibitor] for 7 d, and then half of the seedlings in each treatment were cultured at 25 °C, and the other half of seedlings were exposed to 15 /6 °C (day/night) for 4 d. Data are expressed as mean ± standard error; n = 3. Different letters denote significant differences at P ≤ 0.05 according to Duncan’s multiple range tests.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effects of SNP on the activities and gene expression of sucrose-metabolizing enzymes in melon leaves under chilling stress.
It is well known that sucrose is synthesized by SPS and SS, whereas AI and NI are involved with sucrose decomposition (Burger and Schaffer, 2007). Comparing the activities and gene expression levels of these enzymes for different treatments, we observe that, compared with chilling stress alone, exogenous SNP enhances SPS activity 3.64-fold. However, relative to SNP treatment under chilling stress, Hb, L-NAME, and tungstate treatments decreased SPS activity 53.62%, 59.81%, and 55.33%, respectively (Fig. 2A). Although chilling stress increased SS activity, it is not significantly affected by SNP under chilling stress (Fig. 2B). Increased AI and NI activities are observed for chilling-stressed melon seedlings. However, exogenous SNP decreased AI and NI activities. In addition, application of scavengers and inhibitors of NO enhanced AI and NI activities compared with SNP treatment in chilling conditions (Fig. 2C–D).
Effect of exogenous nitric oxide on the activities and expression of sucrose-metabolism enzymes in melon seedlings under chilling-stress conditions. SS = sucrose synthesis; AI = acid invertase; NI = neutral invertase.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide on the activities and expression of sucrose-metabolism enzymes in melon seedlings under chilling-stress conditions. SS = sucrose synthesis; AI = acid invertase; NI = neutral invertase.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide on the activities and expression of sucrose-metabolism enzymes in melon seedlings under chilling-stress conditions. SS = sucrose synthesis; AI = acid invertase; NI = neutral invertase.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Additionally, compared with the control, SNP application increased the expression levels of CmSPS and CmSS (Fig. 2E–F). However, exposure to SNP caused a significant decrease in the expression of CmAI in the leaves of the seedlings, which was decreased by 25.90% compared with that of the control (Fig. 2G). SNP treatment had no obvious effect on the expression of CmNI, relative to the control (Fig. 2H). Therefore, exogenous SNP significantly enhances the activity of SPS under chilling stress by upregulating its expression, which is consistent with the increase in sucrose content. The expression of CmSS increased, whereas CmAI expression decreased, which maintains a relative stability of sucrose content under chilling stress. There were no obvious differences in the activities and gene expression of SPS, SS, AI, and NI among all of the treatments under control condition (Fig. 2).
Effects of SNP on the activities and gene expression of antioxidant enzymes in melon leaves under chilling stress.
Antioxidant enzymes play an important protective role in plants under chilling stress. As shown in Fig. 3, exposure to chilling stress resulted in a drastic increase in antioxidant enzyme activities, including those of SOD, POD, CAT, and APX, compared with the control. Furthermore, the application of SNP under chilling stress enhanced the activities of SOD, POD, CAT, and APX by 26.98%, 33.68%, 37.50%, and 31.64%, respectively, relative to the control (Fig. 3A–D). NO scavenger and inhibitor treatments inhibited the activities of antioxidant enzymes in melon leaves under chilling stress. For instance, the SOD activities decreased by ≈19.87%, 31.13%, and 21.26% under Hb, L-NAME, and tungstate treatment, respectively, compared with that for SNP treatment alone (Fig. 3A). Furthermore, treatments with the scavenger and inhibitor led to lower levels of antioxidant enzyme activities under chilling stress condition, compared with the control (Fig. 3A–D).
Effect of exogenous nitric oxide (NO) on the activities and relative expression levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in leaves of melon seedling under chilling-stress conditions. The expression levels of CmSOD, CmPOD, CmCAT, and CmAPX were quantified by real-time polymerase chain reaction, normalized to the host actin gene and set relative to control sample according to the 2-ΔΔCt method.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the activities and relative expression levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in leaves of melon seedling under chilling-stress conditions. The expression levels of CmSOD, CmPOD, CmCAT, and CmAPX were quantified by real-time polymerase chain reaction, normalized to the host actin gene and set relative to control sample according to the 2-ΔΔCt method.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the activities and relative expression levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in leaves of melon seedling under chilling-stress conditions. The expression levels of CmSOD, CmPOD, CmCAT, and CmAPX were quantified by real-time polymerase chain reaction, normalized to the host actin gene and set relative to control sample according to the 2-ΔΔCt method.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Remarkable increases in the expression levels of CmSOD (162.37%), CmPOD (40.00%), CmCAT (16.51%), and CmAPX (9.83%) were observed in chilling-stressed plants sprayed with SNP (Fig. 3E–H). This result indicates that SNP application significantly enhances SOD, POD, CAT, and APX activities by upregulating the expression levels of the corresponding genes, thereby protecting against oxidative stress. The activities and gene expression of antioxidant enzymes showed no significant difference among all the treatments under nonstressed condition.
Effects of SNP on the ROS contents in melon leaves under chilling stress.
In this study, there was no obvious difference in the ROS content among all the treatments under control condition. Significant increases in MDA, O2–, and H2O2 contents under chilling stress conditions are observed. SNP treatment decreased H2O2, and MDA accumulation by 16.78% and 10.33%, respectively, compared with chilling stress treatment (Fig. 4). However, compared with the SNP treatment, the levels of MDA, O2–, and H2O2 after Hb application increased by 32.12%, 32.34%, and 109.24%, respectively. Exposure to L-NAME increased in the MDA, O2–, and H2O2 contents by 14.65%, 56.70%, and 30.79%, respectively, compared with SNP application (Fig. 4).
Effect of exogenous nitric oxide (NO) on the production of superoxide anion radicals (O2–), hydrogen peroxide (H2O2), and malondialdehyde (MDA) in melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the production of superoxide anion radicals (O2–), hydrogen peroxide (H2O2), and malondialdehyde (MDA) in melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the production of superoxide anion radicals (O2–), hydrogen peroxide (H2O2), and malondialdehyde (MDA) in melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effects of SNP on the solutes contents in melon leaves under chilling stress.
Compatible solutes like proline, soluble sugars, and soluble proteins maintain osmoregulation and the integrity of the plasma membrane (Ashraf and Foolad, 2007; Hasanuzzaman et al., 2019; Mansour and Ali, 2017). Our data reveal that all the soluble solute contents increased under chilling stress and that they are further elevated by application of SNP (Supplemental Fig. 2). The proline, soluble sugar, and soluble protein improved by 19.04%, 15.50%, and 8.43%, respectively, over their respective controls. Conversely, exogenous application of Hb on chilling-stressed melon seedlings markedly decreases their soluble sugar, soluble protein, and proline contents by 32.05%, 19.98%, and 22.37% respectively, relative to SNP-treated seedlings. Moreover, melon seedlings treated with L-NAME and tungstate exhibit significant reductions in soluble sugar, soluble protein, and proline contents by 27.37% and 41.09%, 42.31% and 17.40%, and 16.03% and 19.13%, respectively, compared with SNP treatment. There were no obvious differences in soluble solutes content among all treatments under the control condition (Supplemental Fig. 2).
Discussion
The reduction in biomass production of plants under chilling stress is a common response through photoinhibition and oxidative stress (Hu et al., 2010; Wang et al., 2016). Melon is an important thermophilic crop and susceptible to chilling stress. Hence, finding an effective way to cope with chilling stress is of great importance for the melon industry. Previous studies have demonstrated that exogenous NO alleviated the adverse effects of chilling stress in many plant species, including rice and walnut (Dong et al., 2018; Sohag et al., 2020). In the present study, chilling treatment significantly decreased the plant height, stem thickness, and fresh weight of melon plant. The pretreatment with SNP recuperated the growth performance of chilling-stressed melon seedling, perhaps by reducing ROS accumulation and lipid peroxidation (Fig. 4). A similar increase of plant growth was also observed previously in Chinese cabbage (Fan et al., 2014) and tomato (Ahmad et al., 2017) under chilling stress.
Previous research has shown that increased production of NO was observed in cold-stressed plants, which plays a crucial role in enhancing stress tolerance (Liu et al., 2010; Xu et al., 2012). Our experiment revealed that chilling treatment increased the NO content in melon leaves, exogenous application of NO can further increase NO levels, but the NO content was declined by NO scavenger and NO synthesis inhibitor (Supplemental Fig. 1). Likewise, Arabidopsis NO-deficient mutant Atnoa1 impaired with endogenous NO levels was reported to have increased sensitivity to salt stress compared with wild-type plants (Zhao et al., 2007). Therefore, NO, produced by SNP treatment under chilling stress may serve as a signal that could further regulate the physiological and biochemical processes of plants, thus conferring better chilling resistance in melon seedling.
Chl contents are important key pigments to absorb and transport light energy during photosynthesis (Arnao and Hernández, 2010). In the present study, we observed increases of Chl content under chilling stress by SNP application (Supplemental Table 1), which is consistent with Fan et al. (2014) and Hatamzadeh et al. (2015). Previous studies have shown that NO-induced increase in Chl content may be due to increased Fe availability because NO contains iron in its molecule. Iron is directly associated with electron transport chain reactions and Chl biosynthesis (Graziano et al., 2002). Moreover, NO has been shown to prevent stress-induced Chl loss and maintain the activity of PSII, thereby mitigating the reduction in photosynthesis (Anil et al., 1986). Thus, exogenous NO protects Chl from degradation and may improve cold resistance of melon seedlings.
As the major product of photosynthesis, carbohydrates—particularly soluble sugars—can act as osmolytes, antioxidants, and signaling molecules to cope with stress (Gil et al., 2013; Hajihashemil et al., 2018). In many plant species, accumulation of carbohydrates such as sucrose has been observed in response to various stress conditions (Li et al., 2015; Parvaiz and Satyawati, 2008; Richter et al., 2015). SPS is known to be a key enzyme for sucrose synthesis and accumulation, whereas SS and invertases catalyze the hydrolysis of sucrose (Winter and Huber, 2000). In the present study, the content of sucrose significantly elevated by chilling stress could be attributed to the higher SPS activity (Fig. 1). SNP application did not change the levels of sucrose in the leaves, nor did it alter the activities of enzymes involved in their synthesis and catalysis in nonstress conditions (Fig. 2). However, under chilling stress, exogenous SNP treatment mediated the accumulation of sucrose levels, which could be attributed to increased SPS activity and decreased activities of the degrading enzymes AI and NI. In addition, exogenous NO treatment had no obvious effect on the SS activity under chilling stress. Similarly, the results showed that SNP application increased CmSPS and CmSS gene expression and decreased CmAI expression, but SNP addition had little effect on the CmAI expressions under chilling stress (Fig. 2). High carbohydrate levels participate in poplar plant tolerance and are responsible for maintaining the integrity of cell membranes under flooding stress (Béjaoui et al., 2016). NO participates in low-temperature-induced accumulation of carbohydrates and starch in tomato (Amooaghaie and Nikzad, 2013). Thus, all these results suggest that exogenous SNP treatment modulated accumulation of carbohydrates may act as an osmoprotectant that stabilizes cellular membranes to improve chilling stress tolerance in melon plants. Similar conclusions were also drawn by Wu et al. (2011) and Shams et al. (2019). Our results are in agreement with an earlier study in walnut shoots suggesting that exogenous NO alleviated the damage caused by chilling stress by elevating the soluble sugar content (Dong et al., 2018).
When plants are subjected to chilling stress, ROS including H2O2, O2–, and OH– are formed, which results in oxidative damage of cellular membranes and components (Lukatkin et al., 2012; Anwar et al., 2018). In this study, significantly enhanced levels of MDA, H2O2, and O2– content were found in chilling-treated melon seedlings. On the contrary, exogenous NO application reduced the MDA and H2O2 levels in chilling stress (Fig. 4). This result may be caused by the increase in antioxidant enzyme activity resulting from upregulation of CmSOD, CmPOD, CmCat, and CmAPX (Fig. 4). Likewise, several studies have reported that the antioxidant defense system and ROS scavenging can be modulated by NO treatment under various stresses (Ahmad et al., 2016; Dong et al., 2018; Lin et al., 2011). For example, spraying with SNP improves antioxidative defense by increasing the activity of antioxidant enzymes in mustard plants (Sami et al., 2020). However, levels of antioxidant enzymes decreased upon NO treatment in Oryza sativa L. under arsenic stress (Praveen and Gupta, 2018). NO reduces the activities of antioxidant enzymes because it acts directly as an ROS scavenger (Wei et al., 2019). Therefore, it was speculated that reducing ROS content through NO and positive regulation by NO of antioxidants enzyme could be major mechanisms in alleviating the oxidative damage from chilling stress.
Under stress conditions, plant cells accumulate compatible solutes such as proline, soluble sugar, and protein to maintain the osmotic homeostasis (Hasanuzzaman et al., 2019). Consistent with previous studies, our results reveal that only chilling stress increased the contents of proline, soluble sugar, and protein in melon seedlings. In addition, exogenous NO treatment further promoted the accumulation of these three osmolytes (Supplemental Fig. 1), implying that application of NO increased contents of proline, soluble sugar, and soluble protein, which might be closely related to improved cold resistance in melon. The accumulation of compatible solutes by NO in stressed plants has been found in various plants (Ahmad et al., 2016; Dong et al., 2018; Shams et al., 2019; Sohag et al., 2020). Furthermore, foliar spraying of maize plants with NO under drought stress enhances proline content by inducing the activity of proline-synthesizing enzymes (Majeed et al., 2020). However, NO is not necessary for proline accumulation (Xiong et al., 2012). Therefore, the effect of NO on proline may depend on species, stress type, and stress conditions.
Conclusions
The results of this study indicate that NO application is a good way to alleviate low-temperature stress in plants. The effective ways to improve the chilling tolerance of plants are by breeding, agronomic measures, and exogenous substance application. The beneficial effects of NO treatment appear to be due to the promotion of sucrose accumulation, which occurs by upregulating the expression of sucrose-metabolizing genes and inducing NR activity, leading to enhanced NO production. Moreover, NO application increases Chl and soluble solute (proline, soluble sugars, and soluble proteins) content; reduces ROS accumulation by decreasing MDA, O2–, and H2O2 contents; and elevates the activities and gene expression of antioxidant enzymes (SOD, POD, CAT, and APX), directly or indirectly decreasing excessive intracellular ROS levels. However, the presence of scavengers and inhibitors of NO synthesis (Hb, L-NAME, and tungstate) blocks the effect of NO. Thus, NO application has a positive effect on melon seedlings under chilling-stress conditions.
Literature Cited
Ahmad, P., Ahanger, M.A., Alyemeni, M.N., Wijaya, L. & Alam, P. 2017 Exogenous application of nitric oxide modulates osmolyte metabolism, antioxidants, enzymes of ascorbate-glutathione cycle and promotes growth under cadmium stress in tomato Protoplasma 255 79 93 https://doi.org/10.1007/s00709-017-1132-x
Ahmad, P., Latef, A., Hashem, A., Allah, E.F. & Tran, L.S. 2016 Nitric oxide mitigates salt stress by regulating levels of osmolytes and antioxidant enzymes in chickpea Front. Plant Sci. 7 868 11 https://doi.org/10.3389/fpls.2016.00347
Amooaghaie, R. & Nikzad, K. 2013 The role of nitric oxide in priming-induced low-temperature tolerance in two genotypes of tomato Seed Ence. Res. 23 2 123 131 https://doi.org/10.1017/S0960258513000068
Amrani, A.E., Couée, I., Berthomé, R., Ramel, F. & Sulmon, C. 2019 Involvement of polyamines in sucrose-induced tolerance to atrazine-mediated chemical stress in Arabidopsis thaliana J. Plant Physiol. 238 7 1 11 https://doi.org/10.1016/j.jplph.2019.04.012
Anil, G., Chandra, S.S. & Prasanna, M. 1986 Effect of temperature on photosynthetic activities of senescing detached wheat leaves Plant Cell Physiol. 27 1 117 126 https://doi.org/10.1094/Phyto-76-124
Anwar, A., Bai, L., Miao, L., Liu, Y., Li, S., Yu, X. & Li, Y. 2018 24-epibrassinolide ameliorates endogenous hormone levels to enhance low-temperature stress tolerance in cucumber seedlings Int. J. Mol. 19 9 2497 https://doi.org/10.3390/ijms19092497
Arnao, M.B. & Hernández, R.J. 2010 Protective effect of melatonin against chlorophyll degradation during the senescence of barley leaves J. Pineal Res. 46 1 58 63 https://doi.org/10.1111/j.1600-079X.2008.00625.x
Ashraf, M. & Foolad, M.R. 2007 Roles of glycine betaine and proline in improving plant abiotic stress resistance Environ. Exp. Bot. 59 206 216 https://doi.org/10.1016/j.envexpbot.2005.12.006
Bates, L.S., Waldren, R.P. & Teare, I.D. 1973 Rapid determination of free proline for water-stress studies Plant Soil 39 1 205 207 https://doi.org/10.1007/BF00018060
Béjaoui, Z., Mguis, K., Abassi, M., Albouchi, A. & Lamhamedi, M.S. 2016 Involvement of carbohydrates in response to preconditioning flooding in two clones of Populus deltoides Marsh. × P. nigra L J. Plant Growth Regul. 35 2 492 503 https://doi.org/10.1007/s00344-015-9555-0
Bradford, M.M 1976 A rapid and sensitive method for the quantitation of microgram quantities of protein using the principle of protein-dye binding Anal. Biochem. 6 248-56 3177 3188 https://doi.org/10.1016/0003-2697(76)90527-3
Burger, Y. & Schaffer, A.A. 2007 The contribution of sucrose metabolism enzymes to sucrose accumulation in Cucumis melo J. Amer. Soc. Hort. Sci. 132 5 704 712 https://doi.org/10.21273/JASHS.132.5.704
Buysse, J. & Merckx, R. 1993 An important colorimetric method to quantify sugar content of plant tissue J. Expt. Bot. 44 10 1627 1629 https://doi.org/10.1093/ jxb/44.10.1627
Cakmak, I. & Marschner, H. 1992 Magnesium deficiency and high light intensity enhance activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase in bean leaves Plant Physiol. 98 4 1222 1227 https://doi.org/doi.org/10.1104/pp.98.4.1222
Dey, P.M 1990 Oligosaccharides 189 218 Dey, P.M. Methods in Plant Biochemistry: Carbohydrates Vol. 2 Academic Press London
Dhindsa, R.S., Pulmb-Dhindsa, P. & Thorpe, T.A. 1981 Leaf senescence: Correlated with increased levels of membrane permeability and lipid peroxidation and decreased levels of superoxide dismutase and catalase J. Expt. Bot. 32 1 93 101 https://doi.org/10.1093/jxb/32.1.93
Diao, Q.N., Song, Y.J., Shi, D.M. & Qi, H.Y. 2016 Nitric oxide induced by polyamines involves antioxidant systems against chilling stress in tomato (Lycopersicon esculentum Mill.) seedling J. Zhejiang Univ-SC. B. 17 12 916 930 https://doi.org/10.1631/jzus.B1600102
Ding, Y., Shi, Y. & Yang, S. 2020 Molecular regulation of plant responses to environmental temperatures Mol. Plant 13 4 544 564 https://doi.org/10.1016/j.molp.2020.02.004
Dong, N., Li, Y., Qi, J., Chen, Y. & Hao, Y. 2018 Nitric oxide synthase-dependent nitric oxide production enhances chilling tolerance of walnut shoots in vitro via involvement chlorophyll fluorescence and other physiological parameter levels Scientia Hort. 230 68 77 https://doi.org/10.1016/j.scienta.2017.11.016
Elstner, E.F. & Heupel, A. 1976 A Inhibition of nitrite formation from hydroxylammonium chloride: A simple assay for superoxide dismutase Anal. Biochem. 70 2 616 620 https://doi.org/10.1016/0003-2697(76)90488-7
Fan, H., Du, C. & Xu, Y. 2014 Exogenous nitric oxide improves chilling tolerance of Chinese cabbage seedlings by affecting antioxidant enzymes in leaves Hort. Environ. Biotechnol. 55 3 159 165 https://doi.org/10.1007/s42729-019-00158-0
Fancy, N.N., Bahlmann, A.K. & Loake, G.J. 2017 Nitric oxide function in plant abiotic stress Plant Cell Environ. 40 462 472 https://doi.org/10.1111/pce.12707
Geigenberger, P. & Stitt, M. 1993 Sucrose synthase catalyses a readily reversible reaction in vivo in developing potato tubers and other plant tissues Planta 189 3 329 339 https://doi.org/10.1007/BF00194429
Giannopolitis, C.N. & Ries, S.K. 1977 Superoxide dismutases: I. Occurrence in higher plants Plant Physiol. 59 309 314 https://doi.org/10.1104/pp.59.2.309
Gil, R., Boscaiu, M., Lull, C., Iautista, B., Lido’n, A. & Vicente, O. 2013 Are soluble carbohydrates ecologically relevant for salt tolerance in halophytes? Funct. Plant Biol. 40 9 805 818 https://doi.org/10.1071/FP12359
Gong, H.L. & Chen, Q. 2021 Exogenous sucrose protects potato seedlings against heat stress by enhancing the antioxidant defense system J. Soil Sci. Plant Nutr. 21 1511 1519 https://doi.org/10.1007/s42729-021-00457-5
Graziano, M., Beligni, M.V. & Lamattina, L. 2002 Nitric oxide improves internal iron availability in plants Plant Physiol. 130 1852 1859 https://doi.org/10.1016/B978-044452236-8/50008-3
Guo, A., Hu, Y., Shi, M., Wang, H. & Wang, Y. 2020 Effects of iron deficiency and exogenous sucrose on the intermediates of chlorophyll biosynthesis in Malus halliana PLoS One 15 5 e0232694 https://doi.org/10.1371/journal.pone.0232694
Hajihashemil, S., Noedoostl, F., Geuns, J.M., Djalovic, L. & Siddique, K.H.M. 2018 Effect of cold stress on photosynthetic traits, carbohydrates, morphology, and anatomy in nine cultivars of Stevia rebaudiana Front. Plant Sci. 9 1430 https://doi.org/10.3389/fpls.2018.01430
Hasanuzzaman, M., Anee, T.I., Bhuiyan, T.F., Nahar, K. & Fujita, M. 2019 Emerging role of osmolytes in enhancing abiotic stress tolerance in rice 677 708 Hasanuzzaman, M., Fujita, M., Nahar, K. & Biswas, J.K. Advances in Rice Research for Abiotic Stress Tolerance. Woodhead Publishing Duxford, UK https://doi.org/10.1016/B978- 0-12-814332-2.00033-2
Hatamzadeh, A., Molaahmad, A., Ghasemnezhad, M. & Biglouei, M.H. 2015 The potential of nitric oxide for reducing oxidative damage induced by drought stress in two turfgrass species, creeping bentgrass and tall fescue Grass Forage Sci. 70 3 538 548 https://doi.org/10.1111/gfs.12135
Huber, S.C. & Huber, J.L. 1991 In vitro phosphorylation and inactivation of spinach leaf sucrose-phosphate synthase by an endogenous protein kinase. Biochimica et Biophysica Acta (BBA)- Molecular Cell Research 1091 3 393 400 https://doi.org/10.1016/0167-4889(91)90205-C
Hu, M., Shi, Z., Zhang, Z., Zhang, Y. & Hui, L. 2012 Effects of exogenous glucose on seed germination and antioxidant capacity in wheat seedlings under salt stress Plant Growth Regulat. 68 2 177 188 https://doi.org/10.1007/s10725-012-9705-3
Hu, W.H., Wu, Y., Zeng, J.Z., He, L. & Zeng, Q.M. 2010 Chill-induced inhibition of photosynthesis was alleviated by 24-epibrassinolide pretreatment in cucumber during chilling and subsequent recovery Photosynthetica 48 4 537 544 https://doi.org/10.1007/s11099-010-0071-y
Kaur, S., Gupta, A.K. & Kaur, N. 2003 Indole acetic acid mimics the effect of salt stress in relation to enzymes of carbohydrate metabolism in chickpea seedlings Plant Growth Regulat. 39 1 91 98 https://doi.org/10.1023/A:1021858802856
Kumar, S., Sreeharsha, R.V., Mudalkar, S., Sarashetti, P.M. & Reddy, A.R. 2017 Molecular insights into photosynthesis and carbohydrate metabolism in Jatropha curcas grown under elevated CO2 using transcriptome sequencing and assembly Sci. Rep. 7 11066 https://doi.org/10.1038/s41598-017-11312-y
Lichtenthaler, H.K. & Wellburn, A.R. 1983 Determination of total carotenoids and chlorophylls a and b of leaf extracts in different solvents Biochem. Soc. Trans. 11 5 591 592 https://doi.org/10.1042/bst0110591
Lin, C.C., Jih, P.J., Lin, H.H., Lin, J.S., Chang, L.L. & Shen, Y.H. 2011 Nitric oxide activates superoxide dismutase and ascorbate peroxidase to repress the cell death induced by wounding Plant Mol. Biol. 77 3 235 249 https://doi.org/10.1007/s11103-011-9805-x
Li, T., Heuvelink, E. & Marcelis, L.F.M. 2015 Quantifying the source sink balance and carbohydrate content in three tomato cultivars Front. Plant Sci. 6 416 https://doi.org/10.3389/fpls.2015.00416
Liu, F., Jensena, C. & Andersen, M. 2004 Drought stress effect on carbohydrate concentration in soybean leaves and pods during early reproductive development: Its implication in altering pod set Field Crops Res. 86 1 1 13 https://doi.org/10.1016/S0378-4290(03)00165-5
Liu, Y., Jiang, H., Zhao, Z. & An, L. 2010 Nitric oxide synthase like activity dependent nitric oxide production protects against chilling-induced oxidative damage in Chorispora bungeana suspension cultured cells Plant Physiol. Biochem. 48 12 936 944 https://doi.org/10.1016/j.plaphy.2010.09.001
Lukatkin, A.S., BrazaitytÄ—, A., Bobinas, C. & Duchovskis, P. 2012 Chilling injury in chilling-sensitive plants: A review Zemdirbyste 99 2 111 124
Majeed, S., Nawaz, F., Naeem, M., Ashraf, M.Y., Ejaz, S., Ahmad, K.S., Tauseef, S., Farid, G., Khalid, I. & Mehmood, K. 2020 Nitric oxide regulates water status and associated enzymatic pathways to inhibit nutrients imbalance in maize (Zea mays L.) under drought stress Plant Physiol. Biochem. 155 147 160 https://doi.org/10.1016/j.plaphy.2020.07.005
Mansour, M.M. & Ali, E.F. 2017 Evaluation of proline functions in saline conditions Phytochemistry 140 52 68 https://doi.org/10.1016/j.phytochem.2017.04.016
Nakano, Y. & Asada, K. 1981 Hydrogen peroxide is scavenged by ascorbate-specific peroxidase in spinach chloroplasts Plant Cell Physiol. 22 5 867 880 https://doi.org/10.1093/oxfordjournals.pcp.a076232
Parvaiz, A. & Satyawati, S. 2008 Salt stress and phytobiochemical responses of plants—A review Plant Soil Environ. 54 3 89 99 https://doi.org/10.17221/2774-PSE
Patterson, B.D., MacRae, E.A. & Ferguson, I.B. 1984 Estimation of hydrogen peroxide in plant extracts using titanium (IV) Anal. Biochem. 139 2 487 492 https://doi.org/10.1016/0003-2697(84)90039-3
Paull, R 1990 Chilling injury of crops of tropical and subtropical origin 7 36 Wang, C.Y. Chilling injury of horticultural crops. CRC Press Boca Raton, FL
Praveen, A. & Gupta, M. 2018 Nitric oxide confronts arsenic stimulated oxidative stress and root architecture through distinct gene expression of auxin transporters, nutrient related genes and modulates biochemical responses in Oryza sativa L Environ. Pollut. 240 SEP 950 962 https://doi.org/10.1016/j.envpol.2018.04.096
Ranwala, A.P. & Miller, W.B. 2010 Sucrose-cleaving enzymes and carbohydrate pools in Lilium longiflorum floral organs Physiol. Plant. 103 4 541 550 https://doi.org/10.1034/j.1399-3054.1998.1030413.x
Richter, J.A., Erban, A., Kopka, J. & Zörb, C. 2015 Metabolic contribution to salt stress in two maize hybrids with contrasting resistance Plant Sci. 233 107 115 https://doi.org/10.1016/j.plantsci.2015.01.006
RodrÃguez-López, J.N., EspÃn, J.C., Amor, F.D., Tudela, J., MartÃnez, V. & Cerdá, A. 2000 Purification and kinetic characterization of an anionic peroxidase from melon (Cucumis melo L.) cultivated under different salinity conditions J. Agr. Food Chem. 48 5 1537 1541 https://doi.org/10.1021/jf9905774
Rosa, M., Hilal, M., González, J.A. & Prado, F.E. 2004 Changes in soluble carbohydrates and related enzymes induced by low temperature during early developmental stages of quinoa (Chenopodium quinoa) seedlings J. Plant Physiol. 161 6 683 689 https://doi.org/10.1078/0176-1617-01257
Ruelland, E., Vaultier, M.N., Zachowski, A. & Hurry, V. 2009 Cold signaling and cold acclimation in plants Adv. Bot. Res. 49 35 150 https://doi.org/10.1016/S0065-2296(08)00602-2
Rufty, T.W. & Huber, S.C. 1983 Changes in starch formation and activities of sucrose phosphate synthase and cytoplasmic fructose-1,6-bisphosphatase in response to source-sink alterations Plant Physiol. 72 2 474 480 https://doi.org/10.1104/pp.72.2.474
Salerno, G.L. & Curatti, L. 2003 Origin of sucrose metabolism in higher plants: When, how and why? Trends Plant Sci. 8 2 63 69 https://doi.org/10.1016/S1360-1385(02)00029-8
Sami, F., Siddiqui, H. & Hayat, S. 2020 Nitric oxide-mediated enhancement in photosynthetic efficiency, ion uptake and carbohydrate metabolism that boosts overall photosynthetic machinery in mustard plants J. Plant Growth Regul. 40 3 1088 1110 https://doi.org/10.1007/s00344-020-10166-5
Schaffer, A.A., Aloni, B. & Fogelman, E. 1987 Sucrose metabolism and accumulation in developing fruit of Cucumis Phytoche. 26 7 1883 1887 https://doi.org/10.1016/S0031-9422(00)8172 1-5
Shams, M., Ekinci, M., Ors, S., Turan, M. & Yildirim, E. 2019 Nitric oxide mitigates salt stress effects of pepper seedlings by altering nutrient uptake, enzyme activity and osmolyte accumulation Physiol. Mol. Biol. Plants 25 3 1149 1161 https://doi.org/10.1007/s12298-019-00692-2
Sharma, A., Soares, C., Sousa, B., Martins, M., Kumar, V., Shahzad, B., Sidhu, G.P.S., Bali, A.S., Asgher, M., Bhardwaj, R., Thukral, A.K., Fidalgo, F. & Zheng, B. 2020 Nitric oxide-mediated regulation of oxidative stress in plants under metal stress: A review on molecular and biochemical aspects Physiol. Plant. 168 318 344 https://doi.org/10.1111/ppl.13004
Simontacchi, M., GarcÃa-Mata, C., Bartoli, C.G., Santa-MarÃa, G.E. & Lamattina, L. 2013 Nitric oxide as a key component in hormone-regulated processes Plant Cell Rep. 32 853 866 https://doi.org/10.1007/s00299-013-1434-1
Sohag, A.A.M., Tahjib-Ul-Arif, M., Afrin, S., Khan, M.K., Hannan, M.A., Skalicky, M., Mortuza, M.G., Brestic, M., Houssain, M.A. & Murata, Y. 2020 Insights into nitric oxide-mediated water balance, antioxidant defence and mineral homeostasis in rice (Oryza sativa L.) under chilling stress Nitric Oxide 100 7 16 https://doi.org/10.1016/j.niox.2020.04.001
Theocharis, A., Clement, C. & Barka, E.A. 2012 Physiological and molecular changes in plants grown at low temperatures Planta 235 1091 1105 https://doi.org/10.1007/s00425-012-1641-y
Thomas, R.L., Jen, J.J. & Morr, C.V. 1981 Changes in soluble and bound peroxidase, IAA oxidase during tomato fruit development J. Food Sci. 47 1 158 161 https://doi.org/10.111 1/j.1365-2621.1982.tb11048.x
Tossi, V., Lamattina, L. & Cassia, R. 2009 An increase in the concentration of abscisic acid is critical for nitric oxide-mediated plant adaptive responses to UV-B irradiation New Phytol. 181 4 871 879 https://doi.org/10.1111/j.1469-8137.2008.02722.x
Wang, L.Z., Wang, L.M., Xiang, H.T., Luo, Y. & Li, R. 2016 Relationship of photosynthetic efficiency and seed-setting rate in two contrasting rice cultivars under chilling stress Photosynthetica 54 581 588 https://doi.org/10.1007/s11099-016-0648-1
Wasternack, C., Stenzel, I., Hause, B., Hause, G., Kutter, C., Maucher, H., Neumerkel, J., Feussner, I. & Miersch, O. 2006 The wound response in tomato-role of jasmonic acid J. Plant Physiol. 163 3 297 306 https://doi.org/10.1016/j.jplph.2005.10.014
Wei, L., Zhang, J., Wang, C. & Liao, W. 2019 Recent progress in the knowledge on the alleviating effect of nitric oxide on heavy metal stress in plants Plant Physiol. Biochem. 147 161 171 https://doi.org/10.1016/j.plaphy.2019.12.021
Winter, H. & Huber, S.C. 2000 Regulation of sucrose metabolism in higher plants: Localization and regulation of activity of key enzymes Crit. Rev. Plant Sci. 19 31 67 https://doi.org/10.1080/10409230008984165
Wu, X., Zhu, W., Zhang, H., Ding, H. & Hong, J.Z. 2011 Exogenous nitric oxide protects against salt-induced oxidative stress in the leaves from two genotypes of tomato (Lycopersicom esculentum Mill.) Acta Physiol. Plant. 33 1199 1209 https://doi.org/10.1007/s11738-010-0648.-x
Xing, W.W., Li, L., Gao, P., Li, H., Shao, Q., Shu, S., Sun, J. & Guo, S. 2015 Effects of grafting with pumpkin rootstock on carbohydrate metabolism in cucumber seedlings under Ca (NO3)2 stress Plant Physiol. Biochem. 87 124 132 https://doi.org/10.1016/j.plaphy.2014.12.011
Xiong, J., Zhang, L., Guan, F. & Fu, G. 2012 Drought-induced proline accumulation is uninvolved with increased nitric oxide, which alleviates drought stress by decreasing transpiration in rice J. Plant Res. 125 1 155 164 https://doi.org/10.1007/s10 265-011-0417-y
Xu, M., Dong, J., Zhang, M., Xu, X. & Sun, L. 2012 Cold-induced endogenous nitric oxide generation plays a role in chilling tolerance of loquat fruit during postharvest storage Postharvest Biol. Technol. 65 5 12 https://doi.org/10.1016/j.postharvbio.2011.10.008
Xu, J., Wang, W., Yin, H., Liu, X., Hong, S. & Mi, Q. 2010 Exogenous nitric oxide improves antioxidative capacity and reduces auxin degradation in roots of Medicago truncatula seedlings under cadmium stress Plant Soil 326 321 330 https://doi.org/10.1007/s11104-009-0011-4
Zeng, F., Sun, F., Li, L., Liu, K. & Zhan, Y. 2014 Genome-scale transcriptome analysis in response to nitric oxide in birch cells: Implications of the triterpene biosynthetic pathway PLoS One 9 116 157 https://doi.org/10.1371/journal.pone.0116157
Zhang, L., Guo, X., Zhang, Z., Wang, A. & Zhu, J. 2021 Cold-regulated gene LeCOR413PM2 confers cold stress tolerance in tomato plants Gene 764 145097 https://doi.org/10.1016/j.gene.2020.145097
Zhang, T., Che, F., Zhang, H., Pan, Y., Xu, M., Ban, Q., Han, Y. & Rao, J. 2017 Effect of nitric oxide treatment on chilling injury, antioxidant enzymes and expression of the CmCBF1 and CmCBF3 genes in cold-stored Hami melon (Cucumis melo L.) fruit Postharvest Biol. Technol. 127 88 98 https://doi.org/10.1016/j.postharvbio.2017.01.005
Zhao, M.G., Tian, Q.Y. & Zhang, W.H. 2007 Nitric oxide synthase-dependent nitric oxide production is associated with salt tolerance in Arabidopsis Plant Physiol. 144 1 206 217 https://doi.org/10.1104/pp.107.096842
Zhu, H., Ai, H., Hu, Z., Du, D., Sun, J., Chen, K. & Chen, L. 2020 Comparative transcriptome combined with metabolome analyses revealed key factors involved in nitric oxide (NO)-regulated cadmium stress adaptation in tall fescue BMC Genomics 21 601 613 https://doi.org/10.1186/s12864-020-07017-8
Effect of exogenous nitric oxide (NO) on the NO content and nitrite reductase (NR) activity of melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the NO content and nitrite reductase (NR) activity of melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on the NO content and nitrite reductase (NR) activity of melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on proline, soluble protein, and soluble sugar contents of melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on proline, soluble protein, and soluble sugar contents of melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous nitric oxide (NO) on proline, soluble protein, and soluble sugar contents of melon seedlings under chilling-stress conditions.
Citation: HortScience 57, 10; 10.21273/HORTSCI16677-22
Effect of exogenous sodium nitroprusside on the chlorophyll contents of melon seedlings under chilling stress.
