The rapeseed transcription factor BnabZIP1 modulates defense responses in Arabidopsis

Rapeseed ( Brassica napus ) suffers substantial losses from diverse pathogens. Transcription factors (TFs) regulate immune-associated transcriptional reprogramming during pathogen invasion. However, the function of rapeseed bZIP TFs in pathogen defense remains largely unknown. A previously uncharacterized Sclerotinia sclerotiorum -induced rapeseed group I bZIP TF, BnabZIP1 , was investigated through heterologous expression in Arabidopsis thaliana . BnabZIP1 transgenic lines (BnabZIP1-OE) enhanced resistance to hemibiotrophic bacterium Pseudomonas syringae pv. tomato DC3000 ( Pst DC3000). This phenotype was associated with reduced coronatine-triggered stomatal reopening and increased callose deposition. BnabZIP1-OE lines decreased sensitivity to exogenous methyl jasmonate and accumulated lower levels of jasmonic acid (JA) after Pst DC3000 infection. In addition, BnabZIP1 contributes to early pattern-triggered immunity responses, as BnabZIP1-OE lines elevated flg22-triggered reactive oxygen species production and mitogen-activated protein kinase (MAPK) phosphorylation. Conversely, BnabZIP1-OE lines compromised defense responses against necrotrophic pathogen S. sclerotiorum and Botrytis cinerea . Overall, BnabZIP1 was associated with resistance to Pst DC3000 but susceptibility to S. sclerotiorum in Arabidopsis. These results provide new insights into the roles of rapeseed bZIP TFs in plant immunity and establish a foundation for future functional studies in rapeseed.