Genome-Wide Identification of Gene Family in Six Cucurbitaceae Species and Its Expression Profiles in Melon.

The carotenoid cleavage dioxygenase (CCD) gene family in plants comprises two subfamilies: CCD and 9-cis-epoxycarotenoid dioxygenase (NCED). Genes in the subfamily are mainly involved in plant responses to abiotic stresses such as salt, low temperature, and drought. Members of the subfamily are the most important rate-limiting enzymes in the biosynthesis of abscisic acid (ABA). In the present study, genome-wide analysis was performed to identify gene members in six Cucurbitaceae species, including watermelon (), melon (), cucumber (), pumpkin (), bottle gourd (), and wax gourd (). A total of 10, 9, 9, 13, 8, 8 genes were identified in the six species, respectively, and these genes were unevenly distributed in different chromosomes. Phylogenetic analysis showed that genes of the six species clustered into two subfamilies: and , with five and three independent clades, respectively. The number of exons ranged from 1 to 15, and the number of motifs were set to 15 at most. The cis-acting elements analysis showed that a lot of the cis-acting elements were implicated in stress and hormone response. Melon seedlings were treated with salt, low temperature, drought, and ABA, and then tissue-specific analysis of expression were performed on the root, stem, upper leaf, middle leaf, female flower, male flower, and tendril of melon. The results showed that genes in family exhibited various expression patterns. Different genes of melon showed different degrees of response to abiotic stress. This study presents a comprehensive analysis of gene family in six species of Cucurbitaceae, providing a strong foundation for future studies on specific genes in this family.