The genetic fusion of thaumatin-like proteins with antimicrobial peptides or receptor-like kinases at different evolutionary time points contributes to plant resistance against Sclerotinia disease

Although gene fusion by the juxtaposition of the coding regions of two independent genes has been investigated in plant metabolism, the role of gene fusion in plant disease resistance remains to be fully elucidated. In this study, we found that gene fusions occurred in rapeseed between antimicrobial thaumatin-like proteins (TLPs) and proline-rich antimicrobial peptides (PRPs), as well as between TLPs and receptor-like kinase proteins (RLKs). Evolutionary analysis revealed that the gene fusion event between TLPs and PRPs occurred approximately 40 million years ago, before the split of Cleomaceae species, while gene fusions between TLPs and RLKs occurred at different time points in Brassicaceae species, and tended to form non-collinear genes due to translocation to a collinear region. A genome-wide association study in a diverse rapeseed panel revealed strong associations between the fused genes BnTLP-RLK1, BnTLP-PRP1, and BnTLP-PRP2 with Sclerotinia disease (SD) resistance, which were functionally verified by individual transgenic expression in Arabidopsis. Furthermore, overexpression of truncated TLP or PRP domains in Arabidopsis exhibited significantly higher SD resistance levels than the wild type, demonstrating that both parts of the gene fusion domains function in defense against SD in plants. Our study provides insights into the cause and consequences of gene fusion in plant disease resistance.