The Roles Of Plant Hormones In Seasonal Bud Dormancy Of Japanese Apricot At Whole Genome-Wide Expression Level

Japanese apricot (Prunus mume Sieb. et Zucc.) originates in China, is a major subtropical fruit crop. Dormancy is one of the most important adaptive mechanisms developed by perennial plants. Dormancy biological process are under strong genetic regulated and, for many types of trees found in perennial plants. In order to investigate the mechanisms of seasonal bud dormancy in Japanese apricot, Illumina sequencing was employed to study differentially expressed genes at the transcriptional level taken ’Taoxingmei’and’Bungo’as the plant materials. We also detected the hormones of seasonal bud dormancy in Japanese apricot by LC-MS/MS methods. And the key differentially expressed genes were verified by qRT-PCR. The main results are as follows:1. Differentially expressed genes (DEGs) at the transcriptional were revealed by Illumina sequencing. The results demonstrated that 19,759,16,375,19,749 and 20,800 tag-mapped genes were sequenced from libraries of paradormancy (R1), endodormancy (R2), ecodormancy (R3) and dormancy release (R4) stages. Moreover,6,199,5,539, and 5,317 genes were differentially expressed in R1 vs. R2, R2 vs. R3, and R3 vs. R4, respectively. Gene Ontology (GO) analysis of dormancy-related genes showed that these were mainly related to the cytoplasm, cytoplasmic part metabolism, intracellular metabolism and membrane-bound organelle metabolism. Pathway-enrichment annotation revealed that highly ranked genes were involved in ribosome pathways and protein processing in the endoplasmic reticulum. We assume that the hormone response genes such as auxin, abscisic acid (ABA), gibberellin (GA), ethylene and jasmonic acid (JA), as well as zinc finger family protein genes, are expressed during the dormancy process in Japanese apricot. Moreover, the expression patterns of differentially expressed genes were verified using qRT-PCR.2. We identified ABA-releated genes, expressed in the flower bud dormancy at four critical stages in the two Japanese apricot cultivars, as well as in the young leaves and vegetative buds, as candidates for the dormancy-controlling genes. Seasonal expression analyses indicated that the ABA-related genes had high transcripts levels in flower buds of the two cultivars in paradormancy. And the ABA-related genes in vegetative buds were highly expressed in November relatively. These results suggest that ABA-related genes are possible important components in the signalling and dormancy transition of buds. We also detected the ABA content of seasonal bud dormancy atfour critical stages in Japanese apricot by LC-MS/MS methods. The results contribute to the further understanding of the bud dormancy mechanism in Japanese apricot.3. We detected the GA content of flower buds and vegetative buds at different periods in Japanese apricot by LC-MS/MS methods. At the same time, we also identified GA20ox gene by qRT-PCR, which expressed in the flower bud dormancy at four critical stages in the two Japanese apricot cultivars, as well as in the vegetative buds and young leaves, as candidates for the dormancy-controlling genes. The results suggested that GA hormone plays a very important role in controlling the release of bud dormancy. And the seasonal expression analyses indicated that the GA20ox plays a prominent role in seasonal dormancy by regulation of GA signaling in Japanese apricot. The results contribute to the further understanding of the GA mediated seasonal dormancy mechanism in Japanese apricot.4. LC-MS/MS was established to determine of JA in flower bud dormancy at four stages in different Japanese apricot cultivars. The sample was extracted by methanol and purified with Agela cleanert SPE-NH2. The separation was performed on a C18. The mobile phase was applied with the gradient elution of acetonitrile-water with 0.05% acetic acid (volume ratio). The identification and quantification were carried out by ESI, second contacts the mass spectrum and negative ions analysis. The result showed that satisfactory linear result have been got with R2 (JA)= 0.9992. The average recoveries and relative standard deviations were 78.18%-97.49% and 1.25%-8.27%, respectively. The method is sensitive and efficient. It is feasible for quantitative determination of JA in Japanese apricot. The results demonstrated that the JA content was significantly up-regulated at ecodormancy and dormancy release compared with paradormancy and endodormancy of the two Japanese apricot cultivars. It indicated that the JA might act as an inhibitory regulator of Japanese apricot dormancy, but played a active role in bud set.