Genome-Wide GRAS Gene Family Analysis Reveals the Classification, Expression Profiles in Melon (Cucumis melo L.)

Melon (Cucumis melo), belonging to the Cucurbitaceae family, is a globally important economic crop. GRAS (GAI, RGA, SCR) genes, which are a type of transcription factor, play a critical role in plant growth and development, including processes such as radial root patterning, light signalling, abiotic/biotic stress, axillary shoot meristem formation, and phytohormone (gibberellin) signal transduction. In this study, the GRAS family in melon was analysed comprehensively with respect to chromosomal location, motif prediction, gene structure, and expression pattern. A total of 37 GRAS genes were first identified in melon, after which a phylogenetic tree was built with the GRAS genes of three model species (Arabidopsis, rice, and sacred lotus) and were divided into nine groups based on the findings of previous studies. Motif and gene structure analysis showed typical conserved domains in all melon GRAS and similar structures in the same subfamilies. The expression analysis of GRAS genes done using RNA-seq data, showed that these genes were differentially expressed in different melon leaves under powdery mildew stress. Furthermore, the real-time quantitative PCR for GRAS genes revealed gene expression corresponding to powdery mildew stress. Our results provide useful information for a better understanding of GRAS genes and provide the foundation for additional functional exploration of the melon GRAS gene family in the powdery mildew stress response.