The transcription factor BnaWRKY75 enhances resistance to the necrotrophic pathogen Sclerotinia sclerotiorum by promoting salicylic acid biosynthesis in oilseed rape.

Abstract

Sclerotinia sclerotiorum, a devastating necrotrophic fungus causing stem rot in oilseed rape, results in significant global yield losses. Deciphering plant-S. sclerotiorum interactions is crucial for disease control. Here, we report that the transcription factor BnaWRKY75 positively regulates resistance to this pathogen. BnaWRKY75 was the most highly induced WRKY genes upon S. sclerotiorum infection. Overexpressing BnaA10.WRKY75 in both Arabidopsis and oilseed rape enhanced resistance to S. sclerotiorum, whereas BnaWRKY75 knockout plants exhibited reduced resistance. RNA sequencing and DNA affinity purification sequencing showed that the isochorismate synthase gene BnaICS1, a key gene required for salicylic acid (SA) biosynthesis, is a potential target of BnaA10.WRKY75. Yeast one-hybrid, dual-luciferase, and electrophoresis mobility shift assays indicated that BnaA10.WRKY75 directly binds to the BnaCnn.ICS1 promoter to activate its transcription, thereby promoting SA biosynthesis and activating SA-dependent defenses. Genetic analysis in Arabidopsis confirmed ICS1 functions downstream of BnaA10.WRKY75. SA treatment significantly enhanced resistance to S. sclerotiorum in oilseed rape, further highlighting the importance of SA in defense against this pathogen. Finally, we observed differences in transcriptional regulation among BnaICS1 homologous genes in allotetraploid oilseed rape. Our findings suggest that the BnaWRKY75-BnaICS1 module regulates SA-dependent resistance to S. sclerotiorum, expanding our understanding of plant immune responses to necrotrophic pathogens.