Characterization and Expression Analysis of Peroxidases and Glucan Synthase Like Genes in Cucumis melo L.

Powdery mildew (PM) is a severe fungal disease for melon cultivation worldwide. Stress resistance related genes could be important tools to address this problem. In this study, we retrieved defense related peroxidase and glucan synthase genes from Melon Genome Database ‘Melonomics’. Thereafter, we analyzed the genes in silico. We conducted protein blast in the NCBI database and found a high degree of homology among them. Based on the highest protein homology we named two isoforms of Cucumis melo peroxidase 2-like genes (CmPrx2-1 and CmPrx2-2) and one glucan synthase1-like gene (CmGLS1). In reverse transcriptionpolymerase chain reaction (PCR), all 3 genes showed organ specific expression in a C. melo line, SCNU1154. Real-time quantitative PCR expression of these 3 genes was conducted in the infected leaf samples by PM fungus Podosphaera xanthii and also treated leaf samples by exogenous phytohormones (salicylic acid and methyl jasmonate). The CmPrx2-2 gene was up-regulated in response to all seven races of PM fungus whereas up-regulation or down-regulation of CmPrx2-1 gene was race-specific. The CmGLS1 gene was down-regulated in response to all races except one race. The CmPrx2-1, CmPrx2-2, and CmGLS1 genes were up-regulated under both salicylic acid and methyl jasmonate treatments but their level of expression was higher in salicylic acid treated plants compared to methyl jasmonate. Therefore, we speculate that defense response of the three tested genes is largely mediated by the salicylic acid signaling pathway under PM infection. Taken together, the data presented herein may be useful resources in the development of PM stress resistant in C. melo L.