Genome-wide identification and characterization of transcription factors involved in defense responses against Sclerotinia sclerotiorum in Brassica juncea

Sclerotinia sclerotiorum could cause significant yield losses of up to 70% in rapeseed cultivation. Nevertheless, the availability of immune or highly resistant germplasm and mechanisms to combat S. sclerotiorum, particularly in B. juncea, remains insufficient. Transcription factors (TFs) are recognized for their critical role in plant defense against S. sclerotiorum. In the present study, a total of 4807 TFs from 48 families were expressed and identified at 12, 24, and 36 h after inoculation (HAI) in two B. juncea lines: G21-912, exhibiting higher S. sclerotiorum resistance (HR), and G21-853, displaying lower S. sclerotiorum resistance (LR). The number of differentially expressed TFs (DETs) between the HR and the LR lines peaked at 24 HAI, with 202 upregulated and 105 downregulated TFs. Through expression and subcellular localization analyses, three candidate DETs, namely BjuA037408 (ETHYLENE RESPONSIVE FACTOR 59, ERF59), BjuB028842 (RELATED TO ABI3/VP1 1, RAV1), and BjuA016484 (WRKY25), were identified as the primary TFs in defense against S. sclerotiorum inoculation. The expression of these three genes was validated in the double haploid lines of BC₃ (the third backcrossing generation) derived from the HR×LR cross. This study serves as a valuable case study for the characterization of TFs associated with defense mechanisms against S. sclerotiorum in B. juncea. The confirmed resistant B. juncea line of HR, along with the three key DETs, is expected to significantly contribute to future breeding efforts aimed at developing Sclerotinia-resistant varieties.