The Study Of Bud Dormancy In Grapes And Its Response Towards ABA And H₂CN₂

Grape(Vitis vinifera L.)is the most widely grown fruit crop worldwide and the table grapes are considered as the major horticultural crop of China,The berries are mainly categorized as table grapes(fresh)and wine grapes(wine).In the current study,we used transcriptome sequencing technology to study the molecular mechanism of dormancy in grapes at different stages of dormancy.During three dormancy stages,6096 transcripts were differentially expressed(log2 ratio? 1,FDR?0.001).Out of the 127 total pathways,Kyoto Encyclopedia of Genes and Genomes(KEGG)analysis revealed that secondary metabolites biosynthesis and plant hormone signaling were found most enriched.Differentially expressed transcripts(DEGs)related to redox activity were found abundantly in the GO biological process category.Secondly,the study was carried out to elucidate promoting and inhibiting effects of hydrogen cynamide(HC)and abscisic acid(ABA)on quiescence release of grape buds.Physiological and molecular approaches were used to explore the mechanisms of quiescence based on metabolic and gene expression analysis.The results indicated that bud quiescence was promoted and regulated by HC and ABA pre-treatment with 5%HC,100 mM ABA and combination of ABA-HC(5%HC+100 mM ABA)during quiescence under forcing condition.Exogenous application of ABA elevated the activities related to superoxide dismutase(SOD),peroxidase(POD)and ascorbate peroxidase(APX),while catalase(CAT)activity was increased during the initial period of forcing and then decreased onwards.The concentration of plant growth hormones including gibberellins(GA)and indole acetic acid(IAA)increased upon HC application but decreased the ABA contents under forcing condition.ABA increased the fructose contents during quiescence under forcing condition while sucrose and total soluble sugars peaked in HC treated buds as compared to control.Genes related to ABA pathway,protein phosphatase 2C(PP2C family)were down regulated in the buds treated with HC,ABA and ABA-HC as compared to control while two genes related to GA pathway(GID1 family),out of which one gene(LOC100260853(probable carboxylesterase 8)down regulated during initial period of forcing while the other gene LOC100255710(probable carboxylesterase 8)was up regulated in response to HC and ABA-HC treatments as compared to control.Exogenous application of ABA up regulated the genes related to antioxidant enzymes as compared to control.The gene probable fructose-bisphosphate aldolase chloroplastic-like,was up regulated in response to ABA treatment as compared to control.Thirdly,the study was conducted to investigate the mechanism of ABA and GA signaling during three different stages of dormancy using transcriptomic approach.The results revealed that most of the transcripts related to protein phosphatase 2C(PP2C)were down regulated during Endodormancy(ED)vs Paradormancy(PD)comparison.The three transcripts related to PYR/PYLs showed up regulation in summer buds(SB)vs ED while one transcript down regulated in PD vs ED comparison.Four transcripts related to serine/threonine-protein kinase(SnRK2)were down regulated in PD vs ED comparison.In GA signaling pathway,six transcripts encoding DELLA proteins were found down regulated in SB vs ED while 10 transcripts were found up regulated in PD vs ED comparison.Nine genes encoding GID2 proteins were up regulated in PD vs ED comparison while 6 genes were down regulated in SB vs ED comparison,respectively.Taken together,these findings reveal that the underlying molecular and physiological mechanism will be helpful for understanding the mechanism of dormancy.