Supriya Purru

Muskmelon (Cucumis melo L., Cucurbitaceae) is an important fruit crop worldwide. It is considered to be the most variable species in the genus Cucumis, and one of the most diverse among the cultivated vegetables. Moisture stress is one of the major restraining factors for musk melon production. To minimize the yield losses caused by moisture stress, there is a need to identify the genes possessing stress tolerance. The main objective of present study was to identify key genes that play a major role in moisture stress tolerance by de novo assembly and annotation of musk melon transcriptome. Transcriptomic analyses of plant responses to stress are an effective way in which genes, pathways and processes responsible for plant stress tolerance can be identified. In this study, a high-throughput, SOLiD sequencing technology was employed to characterize the de novo transcriptome of musk melon. A total of 47,035,393 and 45,152,235 high quality unique reads for cucumis melo control sample and stress sample were assembled into 12859 and 13448 transcripts, respectively using CAP3, DNA STAR and CLC de novo assembly programs. Merging of assemblies by CAP3 resulted in larger and robust transcripts instead of using a single program alone. This de novo assembly of melon transcriptome from control and stress samples provides a rich source for gene identification. These transcripts were annotated with gene ontology (GO) terms. All the GO terms were classified into 37 functional groups including biological processes, cellular component, and molecular function. Comparison of gene expression levels between control and stress transcriptomes by RNA-Seq mapping revealed that 122 stress responsive genes were commonly expressed in both the samples where as 72 genes were highly up regulated in stress sample such as kinases, DREB genes, heat shock proteins, MYB transcription factors, Zinc- finger, and AP2 / ERF domain containing transcription factors. Among these, 4 genes are involved in path ways such as plant-hormone signal transduction, protein processing in endoplasmic reticulum and Inositol phosphate metabolism. These selected genes will not only facilitate understanding of genetic basis of moisture stress response, but also accelerate genetic improvement in musk melon.