Putative Transcriptional Regulation of HaWRKY33-AOA251SVV7 Complex-Mediated Sunflower Head Rot by Transcriptomics and...

HaWRKY33 is induced by salicylic acid and participates in the disease resistance signaling pathway of sunflower rust disease; however, the transcriptional regulatory mechanism of this protein against Sclerotinia sclerotiorum in sunflowers remains unclear. Given this, we conducted a survey of 426 sunflower accessions at the natural disease nursery in Gannan County and identified a single dominant physiological race, MCG1, using simple sequence repeat methods. Additionally, we performed indoor inoculation tests using this dominant race and obtained disease-resistant varieties, W227 and BC2202-03, as well as susceptible varieties, N241 and Z155. Further, we inoculated the above resistant and susceptible combination materials with MCG1 and conducted transcriptomic analysis and RT-qPCR validation. Through KEGG analysis, we found that HaWRKY33 is involved in the plant-pathogen interaction pathway, suggesting that HaWRKY33 may regulate sunflower defense responses against Sclerotinia sclerotiorum through the plant-pathogen interaction pathway. Finally, yeast two-hybrid screening and AI prediction using AlphaFold 3 revealed strong interactions between ARG-189 and GLU-344 amino acids in the HaWRKY33-AOA251SVV7 proteins, indicating that the HaWRKY33-AOA251SVV7 pattern regulates the sunflower defense response against Sclerotinia sclerotiorum in a transcriptional complex form. In summary, these results provide new insights into the disease resistance mechanisms of sunflowers against Sclerotinia sclerotiorum and promote the development of molecular breeding for sunflower resistance to Sclerotinia sclerotiorum.