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To explore differences in sucrose metabolism between peach fruit subjected to chilling stress (5 °C) and nonchilling stress (10 °C), sucrose concentration as well as the activities and gene expression levels for enzymes associated with sucrose metabolism were compared. Fruits stored at 5 °C accumulated higher concentrations of H2O2 and developed severe chilling injury (CI) compared with fruit kept at 10 °C. Activities and gene expression levels for enzymes related to sucrose metabolism, such as acid invertase (AI), neutral invertase (NI), sucrose synthase (SS), and sucrose phosphate synthase (SPS) were higher in fruit stored at 5 °C than at 10 °C throughout or late in storage. A sharp increase in net sucrose cleavage activity dramatically decreased sucrose concentration and increased reducing sugars at 5 °C. The sucrose concentration at 10 °C increased over the first 21 days and then declined slightly, and was higher than in fruit at 5 °C throughout storage. The increase in net sucrose cleavage activity at 5 °C is contrary to the expectation that biochemical reactions ordinarily proceed more rapidly with increasing temperature. We conclude that chilling stress stimulates the activities and transcription levels of enzymes involved in sucrose metabolism, resulting in increased sucrose cleavage.
Nitrogen (N) is a major element required for crop cultivation and an important factor affecting plant growth and development. Malabar chestnut (Pachira macrocarpa) is an important ornamental potted plant crop whose N requirement has been studied, and a rapid monitoring method to manage N fertilization during its commercial production is yet to be established. Malabar chestnut seedlings were fertilized weekly with 0, 4, 8, 16, or 24 mm N. After 12 weeks, 16 mm N was found to yield the greatest plant growth such as plant height, number of nodes, and total leaf area. Measurements of chlorophyll meter readings, leaf chlorophyll concentration, leaf N concentration, and leaf dry weight all indicated that the optimal level of N fertilization was 16 mm N. A chlorophyll meter can be used to monitor nondestructively whether sufficient N has been supplied to support optimal plant growth. In this study, a chlorophyll meter reading of 46.1 corresponded with a critical leaf N concentration of 2.65%, defined as the leaf N concentration when the leaf dry weight was at 90% of saturation point. Additional N supplied beyond this critical level increased foliar chlorophyll content and improved the rate of net photosynthesis. Therefore, chlorophyll meter readings, which are convenient and nondestructive can serve as a reliable reference for commercial production in monitoring N requirement for optimum growth of malabar chestnut. Weekly fertilization of malabar chestnut with 16 mm N and maintaining leaf chlorophyll meter readings between 46.1 and 58.4 are recommended.
Litchi trees flower at the apex of terminal shoots. Flowering is affected by the maturity of terminal shoots before growth cessation occurs during the winter. In this study, we focused on changes of flowering in three important cultivars, Guiwei, Feizixiao, and Huaizhi, from Dec. 2012 to Mar. 2013 under natural winter conditions. Flowering rate, carbohydrate accumulation, and expression of the flowering-related genes were determined at three different developmental stages of terminal shoots with dark green, yellowish green and yellowish red leaves, respectively. The results showed that the total soluble sugar and starch contents in the dark green leaves were the highest, whereas those in the yellowish red leaves were the lowest. Trees with dark green terminal shoots had the highest flowering rates, whereas those with yellowish green or yellowish red shoots had relatively lower flowering rates. SPAD was highest in dark green leaves and lowest in yellowish red leaves at the start of the trial. The SPAD value of yellowish red leaves slightly increased but did not reach the levels of the dark green leaves, whereas levels of the other leaf stages remained fairly constant. Expression level of the litchi homolog FLOWERING LOCUS C (LcFLC), the floral inhibitor in yellowish red leaves, increased from 16 Jan., whereas that in dark green leaves declined to a level lower than the yellowish red leaves on 4 Feb. Expression level of the litchi homolog CONSTANTS (LcCO), the floral promoter in dark green leaves, was higher than that of yellowish red leaves before 26 Jan. Expression level of the litchi homolog FLOWERING LOCUS T 2 (LcFT2), encoding florigen, was higher in dark green leaves than in the other two leaf types. Our results suggest that terminal shoots should be matured and leaves should turn green for successful flowering. Mature leaves had higher expression levels of the floral promoter and florigen. In litchi production, leaves of the terminal shoots (potential flowering branches) should be dark green during floral induction and differentiation stages, and winter flushes should be removed or killed.
The genus Dendrobium is important in traditional Chinese herbal medicine, and the precise identification of Dendrobium species is critical for the treatment and for pharmacological research. In the present study, a ribosomal DNA (rDNA) internal transcribed spacer (ITS) region-based analysis was used to ascertain the phylogenetic relationship among 20 Dendrobium species. The lengths of the ITS regions among the 20 species ranged from 636 to 653 bp, and the identities of the rDNA regions among the different species ranged from 75.7% to 99.1%. The results also showed that the ITS1 and ITS2 regions exhibit more variation than the 5.8S rDNA. A phylogenetic tree derived from the ITS sequence indicated that six medicinal Dendrobium species, of which five are common medicinal plants in the Taiwan market, were closely related and shared a common clade. Multiplex polymerase chain reaction (PCR) amplification was successfully performed to identify the six medicinal Dendrobium species, and amplification refractory mutation system (ARMS) PCR was used to distinguish D. tosaense specifically from the 19 other Dendrobium species. The established PCR-based (multiplex and ARMS) analyses can be used for the authentication of the raw materials of medicinal Dendrobium from other species.
As a wild apple species native to central Asia, Malus sieversii (Ledeb.) Roem. is distributed in a wide region covering most of the Tienshan Mountains. Malus sieversii is a useful genetic pool for apple breeding since rich with diversity. In this paper, we first describe the species range of this endangered species. We then describe an in situ reserve that has been established. We also investigated some reproductive characteristics of M. sieversii including pollen germination, seed dormancy, and seed viability. Both stratification and seedcoat removal efficiently released seed dormancy and accelerated seed germination. Pollen germination rate is around 60%. Our data suggest that injurious insects and human activities, rather than reproductive characters, limit the renewal of M. sieversii.
The DNA binding with one finger (Dof), as an important transcription factor, plays an important role in growth and development, primary and secondary metabolism, stress resistance, and plant hormone signal transduction. However, the identification and analysis of the Dof transcription factor family in Rosa is rarely reported. In this study, 28 Rosa chinensis Dof (RcDof) members were identified, which were located on seven chromosomes. The RcDofs were divided into 12 subfamilies according to evolutionary analysis. Through motif, gene structure, and cis-acting element analyses of the 12 subfamilies, the functions of RcDofs were analyzed and predicted. Furthermore, the Dof members in R. chinensis ‘Old Blush’ and another three species (Arabidopsis thaliana, Oryza sativa, and Zea mays) were systematically analyzed. Twelve subfamilies were found in these four species and the motifs and gene structures of Dof members in each subfamily were similar, which further proves that the RcDofs analysis is accurate. Through an intra- and interspecies collinearity analysis, it was found that the collinearity between A. thaliana and R. chinensis is closer in comparison. Tissue expression analysis of RcDofs was by quantitative reverse-transcription polymerase chain reaction (PCR). Quantitative real-time PCR analysis showed expressions of the RcDofs are tissue specific. The RcDofs had higher expression in leaves, roots, and flowers than other tissues. Taken together, this study provides valuable information for future research on functional exploration of RcDof genes and molecular breeding in Rosa.
Sequencing amplification fragments produced using simple-sequence repeat (SSR) primer pairs pchgms2 and UDP96008 in `Dayezhugan' japanese apricot showed that SSRs obtained included a microsatellite locus originally identified in peach. The microsatellite sequence homogeneity between UDP96008 in japanese apricot in this study and UDP96008 in the peach in GenBank was 98%. Twenty-four japanese apricot genotypes originating in diverse geographic areas had been identified with 14 SSR primer pairs developed in different species of Prunus. In total, 129 alleles were obtained and per primer pairs detected 2.5 alleles on the average. The results from cluster analysis showed that the genetic distance between `Nanhong' and `Zhonghong' was the closest, and cultivars from China and from Japan could not be separated completely.
An efficient biolistic transformation system of banana combined with a liquid medium selection system was developed during this study. An embryogenic cell suspension (ECS) of Musa acuminata cv. Baxi (AAA) was bombarded with a particle delivery system. After 7 days of restoring culture in liquid M2 medium, embryogenic cells were transferred to a liquid selection M2 medium supplemented with 10 μg/mL hygromycin for resistance screening. The untransformed cell clusters were inhibited or killed, and a small number of transformants proliferated in the liquid selection medium. After the 0th, first, second, and third generation of antibiotic screening, there were 0, 65, 212, and 320, respectively, vitality-resistant buds obtained from a 0.5-mL packed cell volume (PCV) of embryogenic cell suspension. The β-glucuronidase (GUS) staining, polymerase chain reaction (PCR) analysis, and Southern blot hybridization results all demonstrated a 100% positive rate of regenerated resistant seedlings. Interestingly, the number of buds obtained through third-generation screening was almost equal to that obtained from the original ECS in M2 medium without antibiotics. These results suggested that the liquid medium selection system facilitated the proliferation of a positive transgenic ECS, which significantly improved the regeneration rate of transformants. This protocol is suitable for the genetic transformation of all banana genotypes and is highly advantageous to varieties with low callusing potential.
Hydrogen sulfide (H2S) has been proven to be a multifunctional signaling molecule in plants. In this study, we attempted to explore the effects of H2S on the climacteric fruit tomato during postharvest storage. H2S fumigation for 1 d was found to delay the peel color transition from green to red and decreased fruit firmness induced by ethylene. Further investigation showed that H2S fumigation downregulated the activities and gene expressions of cell wall–degrading enzymes pectin lyase (PL), polygalacturonase (PG), and cellulase. Furthermore, H2S fumigation downregulated the expression of ethylene biosynthesis genes SlACS2 and SlACS3. Ethylene treatment for 1 d was found to induce the expression of SlACO1, SlACO3, and SlACO4 genes, whereas the increase was significantly inhibited by H2S combined with ethylene. Furthermore, H2S decreased the transcript accumulation of ethylene receptor genes SlETR5 and SlETR6 and ethylene transcription factors SlCRF2 and SlERF2. The correlation analysis suggested that the fruit firmness was negatively correlated with ethylene biosynthesis and signaling pathway. The current study showed that exogenous H2S could inhibit the synthesis of endogenous ethylene and regulate ethylene signal transduction, thereby delaying fruit softening and the ripening process of tomato fruit during postharvest storage.