Transcriptome uncovers BnaFBH3-mediated regulatory networks associated with tolerant to abiotic stress in Brassica napus

Environmental stresses limit various stages of plant growth, including germination, seedling establishment, reproductive growth, yield and quality. Rapeseed (Brassica napus L.) is a crucial oil crop in the world, yet salt and osmotic stresses cause significant losses in its production annually. This study aimed to comprehend the molecular mechanisms of response to salt and osmotic stresses in rapeseed, achieved by analyzing transcriptomes from rapeseed roots treated with salt and PEG (Polyethylene Glycol 6000). A total of 5251 (up/down: 2416/2835), 5169 (up/down: 2532/2637), and 7375 (up/down: 4014/3361) differentially expressed genes (DEGs) were identified in salt treatment 3 h, 6 h, and 12 h, respectively. A set of 2789 (up/down: 1142/1647), 6807 (up/down: 2757/4050), and 2524 (up/down: 1258/1266) DEGs were identified in PEG treatment 3 h, 6 h, and 12 h, respectively. Among those DEGs, 1809 early regulated genes were found in both salt treatment 3 h and PEG treatment 3 h. There are 165 early expressed transcription factors in the 1809 DEGs. One bHLH transcription factor BnaFBH3-C06 (BnaC06g04380D/BnaC06G0054400ZS), a homologous gene of Arabidopsis AtFBH3/AtbHLH122, was strongly induced by salt, osmotic, PEG, low temperature and ABA. Overexpression of BnaFBH3-C06 resulted in early flowering and increased the salt tolerance in rapeseed, as evidenced by higher survival rate and chlorophyll content compared to the wild type (WT) under NaCl treatment. KEGG, GO, and PPI-network analysis showed that BnaFBH3-C06 associated with ABA signaling and stress-related genes in response to salt and osmotic stresses in rapeseed. These findings of this study provide insights into the response for abiotic stresses in rapeseed and offer an ideal candidate gene (BnaFBH3-C06) for molecular breeding of salt-tolerant and early-maturing rapeseed cultivars.