A Pathogenesis-Related Protein 1 of Cucurbita moschata responds to powdery mildew infection

Abstract Background: Pumpkin ( Cucurbita moschata Duch.) productivity is severely hindered by powdery mildew worldwide. The causative agent of pumpkin PM is Podosphaera xanthii , a biotrophic fungus. To identify genes involved in the defense response to PM attack, we performed a transcriptomic analysis of a highly-resistant pumpkin genotype by RNA-sequencing. Pathogenesis-related protein 1 (PR1) is among the most abundantly produced proteins in plants responding to pathogen attacks. In this study, we identified and investigated the effects of CmPR1 gene from C. moschata for resistance to powdery mildew. Results: Subcellular localization assay in Arabidopsis protoplasts revealed that CmPR1 is a cytoplasmic protein in plants. The expression of CmPR1 gene was strongly induced by P. xanthii and exogenous ethylene, jasmonic acid and NaCl treatments, but repressed by hydrogen peroxide and salicylic acid treatments. Visual disease symptoms, histological observations of fungal growth and host cell death, and accumulation of H 2 O 2 in transgenic tobacco plants indicated that CmPR1 overexpression significantly enhanced the resistance to Golovinomyces cichoracearum compared to wild type plants during powdery mildew pathogens infection, possibly due to inducing cell death and H 2 O 2 accumulation near infected sites. The expression of PR1a was significantly induced in transgenic tobacco plants in response to G. cichoracearum , suggesting that CmPR1 overexpression positively modulates the resistance to powdery mildew via the SA signaling pathway. Conclusions: These findings indicate that CmPR1 is a defense response gene in C. moschata and and can be exploited to develop disease-resistant crop varieties.