芥菜型油菜耐旱相关miRNA的挖掘及功能研究OA

Due to the influence of karst landforms,Guizhou is more susceptible to drought under extreme weather events,posing a serious threat to rapeseed production.Compared to Brassica napus,Brassica juncea exhibits greater drought tolerance in pro-duction.Therefore,mining drought-tolerant-related genes and elucidating their molecular functions is of great significance for improving stress resistance and yield in rapeseed.MicroRNAs(miRNAs)have been shown to play critical regulatory roles in plant drought stress response,yet studies in B.juncea remain limited.In this study,two B.juncea lines with contrasting drought responses(G160 and G170)were used.Combined small RNA(sRNA)sequencing and molecular functional assays were per-formed to predict and functionally analyze drought-responsive miRNAs and their target genes.A total of 44 known and novel drought-responsive miRNAs were identified.RT-qPCR validated the dynamic expression patterns of eight miRNAs under drought stress,revealing that their expression levels were lower in the drought-tolerant line G170 than in the sensitive line G160.Target gene prediction indicated that some target genes are involved in drought response(e.g.,ATHBs,PCL5)and ABA signaling path-ways(e.g.,AHA1,CAR9).Furthermore,heterologous overexpression of BjuMIR9552a in B.napus was performed.Drought-rehydration tests and physiological/biochemical measurements showed that transgenic plants exhibited lower drought tolerance than wild-type plants.RT-qPCR analysis revealed significant downregulation of AHA family genes in the transgenic lines,suggesting that BjuMIR9552a may negatively regulate drought resistance in rapeseed by targeting AHA family genes.This study identified eight miRNAs that may act as repressors of drought stress;overexpression of BjuMIR9552a reduces drought resistance and downregulates AHA family gene expression.These findings provide a new theoretical basis for further dissecting the miRNA-mediated drought response regulatory network in B.juncea.