Effects of exogenous salicylic acid on flavonoid biosynthesis and expression patterns of related genes in tartary buckwheat
Salicylic acid(SA)is an important signaling molecule that regulates plant secondary metabo-lites.Previous studies have shown that exogenous salicylic acid can promote total flavonoid accumulation and related gene expression in Tartary buckwheat seedlings.However,the effects of flavonoid metabolism in Tartary buckwheat grains are rarely reported.In this study,at the green ripening stage of Tartary buck-wheat grains,the total flavonoid content of'Heifeng 1'was increased by 1.21 times compared with the control when 0.5 mmol L-1 SA was applied externally.A total of 2 317 differentially expressed genes,in-cluding 988 up-regulated and 1 329 down-regulated genes,were identified by comparative transcriptome analysis.KEGG enrichment analysis revealed that the differentially expressed genes were mainly concen-trated in the flavonoid biosynthesis pathway,and 26 key enzyme genes with significant differences in ex-pression were identified in this pathway,phenylalanine ammonia-lyase(PAL)and trans-cinnamate 4-mono-oxygenase(C4H),were both up-regulated and down-regulated,while 4-coumarate-CoA ligase(4CL),chaicone synthase(CHS)and flavanone 3-hydroxylase(F3H)were up-regulated by 1.32-4.33 times.qRT-PCR showed that the expression trend was consistent with that of transcriptome analysis.The promoter analysis of 26 genes of flavonoid metabolism pathway found that 12 genes contained SA response ele-ments,indicating that the key enzyme genes of this pathway were involved in the function of responding to SA signal.Based on weighted coexpression network analysis and homologous gene analysis,3 tran-scription factors were identified that regulate flavonoid synthesis mediated by exogenous salicylic acid Ft-WRKY7(FtPinG0002142900),FtWRKY2(FtPinG0002177700)and FtWRKY65(FtPinG0002493300).These results suggested that exogenous salicylic acid in-directly regulated the expression level of genes related to flavonoid metabolic pathway,thereby increasing the total flavonoid accumulation in Tartary buckwheat grains.This study preliminarily revealed the molecular mechanism of salicylic acid regulating flavonoid synthesis in Tartary buckwheat grains.It provided some theoretical reference for exogenous SA biospray-ing to enhance the flavonoid in Tartary buckwheat grains and improve its nutritional value.
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