A pathogenesis-related protein 1 of Cucurbita moschata responds to powdery mildew infection
Wei-Li Guo, He-Lian Yang, Jinpeng Zhao, Shi-Jie Bian, Yanyan Guo, Xuejin Chen, Xinzheng Li
Abstract
Pumpkin ( Cucurbita moschata Duch.) productivity is severely hindered by powdery mildew (PM) worldwide. The causative agent of pumpkin PM is Podosphaera xanthii , a biotrophic fungus. Pathogenesis-related protein 1 (PR1) homolog was previously identified from transcriptomic analysis of a PM-resistant pumpkin. Here, we investigated the effects of CmPR1 gene from pumpkin for resistance to PM. Subcellular localization assay revealed that CmPR1 is a cytoplasmic protein in plants. The expression of CmPR1 gene was strongly induced by P. xanthii inoculation at 48 h and exogenous ethylene (ET), jasmonic acid (JA) and NaCl treatments, but repressed by H 2 O 2 and salicylic acid (SA) 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 PM 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 PM via the SA signaling pathway. These findings indicate that CmPR1 is a defense response gene in C. moschata and can be exploited to develop disease-resistant crop varieties.