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

Abstract Sclerotinia sclerotiorum could cause significant yield losses of up to 70% in rapeseed cultivation. However, the availability of immunological or highly resistant germplasms and mechanisms against S. sclerotiorum, particularly in B. juncea, remains limited. Transcription factors (TFs) are known to play a crucial role in plant defense against S. sclerotiorum. In this study, a total of 4,807 TFs from 48 families were expressed and identified within the time frame of 0 h to 36 h after innovation (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 analysis, 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 through real-time qRT-PCR and BC3 (third backcrossing generation) population from HR×LR. This study presents a valuable case study in B. juncea for the characterization of TFs implicated in defense against the S. sclerotiorum inoculation. The confirmed resistant B. juncea line of HR and the three key DETs are anticipated to play a significant role in the future breeding of Sclerotinia-resistant varieties.