Transcriptome and Small-RNA Sequencing Reveals the Response Mechanism of <i>Brassica napus</i> to Waterlogging Stress

Rapeseed (<i>Brassica napus</i>) is highly susceptible to waterlogging during the seedling stage; however, most of the studies on its gene expression under waterlogging stress have focused on transcriptional regulation, with little work conducted on post-transcriptional regulation to date. To elucidate this regulatory network, comparative transcriptome and miRNA analyses in the leaves and roots of rapeseed Zhongshuang11 (ZS11) were performed. Differentially expressed genes (DEGs) and miRNAs (DEmiRNAs) were identified by comparing the normal planting condition (the control group, CKT) with waterlogging treatment (WLT). DEGs identified in leaves and roots were enriched in different metabolic pathways, indicating their distinct mechanisms in response to waterlogging stress. In total, 68 and 82 DEmiRNAs were identified in leaves and roots, respectively, predicted to target 543 and 2122 DEGs in each tissue. Among these, 12 and 9 transcription factors (TFs) were exclusively targeted by DEmiRNAs in leaves and roots, respectively. Notably, six upregulated TFs in leaves were associated with the ethylene response and were predicted targets of bna-miR172 family members, and four TFs in roots participated in the ethylene response pathway. Furthermore, bna-miR169, along with novel-miR-23108 and novel-miR-42624 family members, played crucial roles in waterlogging response of rapeseed. Combining with the determination results of ethylene and jasmonic acid content, a preliminary model of miRNA-mediated gene expression regulation in rapeseed response to waterlogging stress was developed. These findings advance our understanding of transcriptional regulation under waterlogging and lay a theoretical foundation for improving rapeseed waterlogging tolerance.