Search Results
The objective of the study was to determine whether the expression of a cytokinin (CK) biosynthesis gene encoding adenine isopentenyl transferase (ipt) would delay or suppress leaf senescence induced by nitrogen (N) or phosphorus (P) deficiency in a C3 grass species, creeping bentgrass (Agrostis stolonifera). The ipt gene was ligated to a senescence-associated promoter, SAG12, and was transferred into creeping bentgrass using an agrobacterium (Agrobacterium tumefaciens)-mediated transformation technique. Plants from an SAG12-ipt transgenic line (S41) and a null transformant (NT) control line were grown in nutrient solutions with all essential elements or without N (−N) or P (−P) for 21 days. Significant declines in leaf photochemical efficiency (Fv/Fm) and chlorophyll content of mature leaves were detected in NT and SAG12-ipt plants exposed to N or P deficiency. Compared to the NT control line, SAG12-ipt plants had higher levels of Fv/Fm, chlorophyll, and CK contents in leaves, and these differences between the NT control and SAG12-ipt line became more pronounced with treatment duration. The ipt expression was detected in the −P-treated and the −N-treated plants after 21 days, although the level of expression decreased under N or P deficiency. Under −P treatment, root acid phosphatase activity was greater in SAG12-ipt line than in the NT control line. No significant differences in nitrate reductase activity were detected in leaves or roots between the SAG12-ipt and the NT control lines. Our results demonstrated that SAG12-ipt expression suppressed leaf senescence induced by N or P deficiency in a perennial grass species. The suppressing effects on leaf senescence under P deficiency may be related to CK regulation of more efficient use of P in roots of the SAG12-ipt plants.
We studied the effects of exogenous spermidine (Spd) on plant growth and nitrogen metabolism in two cultivars of tomato (Solanum lycopersicum) that have differential sensitivity to mixed salinity-alkalinity stress: ‘Jinpeng Chaoguan’ (salt-tolerant) and ‘Zhongza No. 9’ (salt-sensitive). Seedling growth of both tomato cultivars was inhibited by salinity-alkalinity stress, but Spd treatment alleviated the growth reduction to some extent, especially in ‘Zhongza No. 9’. Exogenous Spd may help reduce stress-induced increases in free amino acids, ammonium (NH4 +) contents, and NADH-dependent glutamate dehydrogenase (NADH-GDH) activities; depress stress-induced decreases in soluble protein and nitrate content; and depress nitrate reductase, nitrite reductase, glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), glutamate oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase (GPT) activities, especially for ‘Zhongza No. 9’. Based on our results, we suggest that exogenous Spd promotes the assimilation of excess toxic NH4 + by coordinating and strengthening the synergistic action of NADH-GDH, GS/NADH-GOGAT, and transamination pathways, all during saline-alkaline stress. Subsequently, NH4 + and its related enzymes (GDH, GS, GOGAT, GOT, and GPT), in vivo, are maintained in a proper and balanced state to enable mitigation of stress-resulted damages. These results suggest that exogenous Spd treatment can relieve nitrogen metabolic disturbances caused by salinity-alkalinity stress and eventually promote plant growth.
Centipedegrass [Eremochloa ophiuroides (Munro) Hack] is a native grass of China, and information on soil adaptation ranges, including acid soils, among centipedegrass cultivars is limited. Therefore, objectives of this study were 1) to conduct a preliminary evaluation of relative aluminum tolerance of 48 centipedegrass accessions plus a cultivar, TifBlair, and a common centipedegrass under aluminum (Al) stress (0 and 1500 μM Al) by using a solution culture method; and 2) to determine Al effects on nutrient uptake between resistant-group and sensitive-group accessions among the 50 accessions and cultivars. Differences were found among accessions and cultivars, and the CV of relative root weight, relative shoot weight, and relative total weight were 39.9%, 32.9%, and 33.6%, respectively. After growing 28 days in an acid subsoil, the resistant-group accessions showed much better growth than the sensitive-group accessions. The Al concentrations in roots and shoots of the two groups of accessions were increased under Al treatment, but most absorbed Al remained in roots with greater Al absorption among the sensitive group compared with the resistant group. The concentrations of phosphorus (P), magnesium (Mg), calcium (Ca), and potassium (K) in the two groups were reduced under Al stress with reductions of 59.3%, 54.8%, 47.9%, and 41.3% in shoots and reductions of 8.70%, 52.5%, 43.2%, and 34.4% in roots, respectively. Under Al stress, differences in P, Mg, and Ca concentrations were found between the two groups; however, differences were not found for K. The resistant-group accessions maintained higher concentrations of Mg and Ca than the sensitive group.
Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a warm-season grass for low-maintenance lawns. The objective of our study was to assess the genetic variation in 10 accessions of buffalograss obtained from the Chinese Academy of Agricultural Sciences by random amplified polymorphic DNA (RAPD) markers. Fourteen of the 60 primers screened generated 72 highly repeatable polymorphic bands. A dendrogram constructed on the basis of the unweighted pair group method arithmetic average clustering algorithm revealed that nine of 10 accessions formed two distinct clusters. Genetic similarity coefficients calculated from the RAPD data ranged from 0.30 to 0.89 with the lowest value of 0.30 measured between No. 4 and No. 7 from Japan and the United States, respectively. The highest value of 0.89 was measured between No. 6 and No. 8 from the United States and Mexico, respectively. The cophenetic correlation coefficient (r) was 0.92, indicative of a very good fit between the data matrix and the resulting cluster analysis. Principal coordinate analysis (PCO) clearly grouped nine accessions on the two axes with a single accession from the United States that did not cluster with others. The PCO clustering pattern corresponded well with the dendrogram. No. 7 from the United States did not cluster with any other accessions either in the dendrogram or on the basis of the PCO.
MicroRNAs (miRNAs) related to phytohormone signal transduction and self-incompatibility may play an important role in the xenia effect. However, associated research in this area is still lacking in rabbiteye blueberry (Vaccinium ashei). In this study, we identified miRNAs, predicted their target genes, performed functional enrichment analysis of the target genes, and screened for miRNAs related to phytohormone signaling and self-incompatibility. A total of 491 miRNAs were identified, of which 27 and 67 known miRNAs as well as 274 and 416 new miRNAs were found in the rabbiteye blueberry cultivars Brightwell and Premier, respectively. Compared with ‘Premier’, 31 miRNAs were upregulated and 62 miRNAs were downregulated in ‘Brightwell’. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis indicated that the 4985 target genes predicted were involved in biosynthesis of amino acids, plant–pathogen interaction, and spliceosome pathways. A total of 10, one, one, five, two, five, and two candidate miRNAs related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling, respectively, in rabbiteye blueberry pollen were identified. Further analysis indicated that novel_miR_49 was a candidate miRNA related to self-incompatibility, and their target gene was maker-VaccDscaff21-snap-gene-21.37. In addition, the KEGG enrichment analysis of the target genes of novel_miR_49 showed that they were involved in the ribosome, aminoacyl-tRNA biosynthesis, and glycosylphosphatidylinositol-anchor biosynthesis pathways. The results revealed that the microRNAs of rabbiteye blueberry pollen regulated to phytohormone signal transduction and self-incompatibility signal transduction based on related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling. Results suggest that more research of the effects of miRNAs on regulation of hormone signal transduction and self-incompatibility is necessary for elucidating the molecular mechanism of the xenia effect.
Solid-state 1H-NMR and 13C-NMR spectroscopy were used to investigate the chemical components of sweet cherry tree leaves under rain-shelter cultivation (RS) and open-field cultivation (CK). The 1H-NMR spectral chemical shifts of RS and CK showed differences in height and integral value. The δ 1–3, δ 3–4, δ 4–6, and δ 6–10 regions were attributed to the hydrogen signals of aliphatic compounds, unsaturated carbohydrate compounds, and aromatic compounds, respectively. Among the four regions, the percentage of signal strength and the integral value of hydrogen signals of RS and CK were 34.25% and 28.34%, 11.64% and 12.26%, 26.71% and 31.06%, 27.4% and 28.34%, respectively. The 13C-NMR results showed that the CK sample had slightly stronger spectral lines and contained slightly more carbon atoms than the RS sample. Sweet cherry leaves contain aromatic and carboxyl carbons, mainly from carboxylic acids, esters, and amides. The alkyl carbons exhibited the lowest ratio, whereas the alkyl and alkoxy carbons were mainly derived from carbohydrates (cellulose, polysaccharides).
Bletilla is an Orchidaceae genus with high medical value, including detumescence, antibacterial, and hemostasis. In this study, detailed estimates of ploidy level, karyotype, and genome size were first obtained, and a comprehensive cytological analysis was carried out to better understand the evolution of the genus. The karyotypes of Bletilla were mainly composed of metacentric and submetacentric chromosomes with lengths ranging from 1.25 to 4.93 μm. There was moderate cytological variation in Bletilla (chromosome number 2n = 32 to 76). Diploid with 2n = 34 and 2n = 36 was detected in Bletilla ochracea and Bletilla formosana, respectively, whereas diploid (2n = 32) was dominant in Bletilla striata, dysploidy (2n = 34, 2n = 36) and polyploid (2n = 48, 51, 64, 76) variations were also observed. Three species had a relatively symmetric karyotype, and which of B. ochracea was more asymmetry. The genome size (1C-values) varied from 2.94 pg (B. striata) to 3.33 pg (B. ochracea), of which B. ochracea was significantly larger than the others (P < 0.05). A positive correlation (P < 0.01) between 1Cx vs. haploid chromosome length (HCL) and asymmetry coefficient of karyotypes (AsK%) was observed.
Marigold (Tagetes erecta) is an important commercial plant because of its ornamental, industrial, and medicinal values. Male-sterile two-type lines are important for heterosis utilization and breeding of marigold. Mining of fertility-related genes may help to elucidate the mechanisms underlying male sterility. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) is a popular and useful tool for analyzing the expression level of a specific gene. Notably, identifying a suitable reference gene is important for data normalization because it affects the accuracy of quantitative analysis. However, at present, no reference genes are available for marigold. During the current study, 10 candidate reference genes were selected and their expression levels in different samples were analyzed by qRT-PCR. The expression level of each gene was analyzed across different developmental stages of male-sterile and male-fertile flower buds by four software programs (geNorm, NormFinder, BestKeeper, and RefFinder). The results showed that different reference genes are required for male-sterile and male-fertile samples, even if they belong to the same line. For male-sterile samples, the ribosomal protein S5/18S ribosomal RNA (RPS5/18S) gene pair was the best reference for qRT-PCR normalization, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) could be used as an alternative. For male-fertile samples, elongation factor 1-alpha (EF1α) and RPS5 were the most suitable reference genes, and Ubiquitin-conjugating enzyme (UBC) could be used as an alternative. Beta-actin (ACTB), tubulin beta (TUB), and phenylalanine ammonia-lyase (PAL) should not be used as reference genes because they were the most unstable genes in flower buds of marigold. The results of the current study may facilitate the selection of reference genes for analyzing the expression patterns of genes involved in flower development related to male sterility in marigold.
Application of sugar alcohol zinc (SA-Zn) spray to apple trees at certain developmental stages can improve fruit quality. Increasing the Zn concentration of fruit can improve nutritional content and promote human health. We conducted foliar application of SA-Zn to 13-year-old ‘Fuji’ apple trees at different developmental stages. The effects of SA-Zn application on Zn concentration, reducing sugar content, and carbohydrate metabolism-related enzyme activity in fruit were investigated. The foliar treatment increased Zn and reducing sugar concentrations significantly in mature fruit. Sorbitol dehydrogenase activity was higher in the fruit of trees treated before budbreak and 3 weeks after flowering compared with the control at the early fruit stage and was higher during fruit expansion in plants treated after termination of spring shoot growth. Mature fruit of trees treated during the fruit expansion stage showed higher sorbitol dehydrogenase activity than the control. Foliar SA-Zn treatment did not have a significant effect on sorbitol oxidase activity in apple fruit. Treatment before budbreak and at 3 weeks after flowering led to a significant increase in the activity of sucrose synthase and acid invertase at the early fruit stage. Treatment during the fruit expansion stage significantly increased the activity of acid invertase at maturity but had no effect on the activity of neutral invertase. Our results indicate that foliar SA-Zn application resulted in biofortification of Zn in apples, which led to higher activity of carbohydrate metabolism-related enzymes and accumulation of sugars.