Genome-Wide Identification and Expression Analysis of the YABBY Gene Family in Bitter Gourd

YABBYs are transcription factors involved in fruit development, leaf polarity establishment, and adaptation to stresses in plants. Bitter gourd (Momordica charantia L.) is an important cucurbit crop, but YABBY genes have not been reported in this species. In this study, the YABBY gene family of bitter gourd was digitally identified using its T2T genome, and the sequence characteristics, phylogenetic relationships, and expression profiles of each gene member were analyzed through bioinformatic and experimental approaches. A total of eight YABBY homologous genes, designated McYABBY1 (Momordica charantia YABBY1) to McYABBY8, were identified and clustered into five clades in the phylogenetic tree, each showing a clear orthologous relationship to a corresponding Arabidopsis gene. RNA-seq data and RT-qPCR revealed distinct expression patterns among McYABBY genes across various organs and fruit developmental stages. Notably, McYABBY3 and McYABBY8 are actively and constitutively expressed during fruit ripening. Additionally, RT-qPCR showed that members of the McYABBY gene family exhibit differential expression in response to abiotic stress, with six up-regulated and two down-regulated under salt stress, and five up-regulated, two down-regulated, and one relatively unchanged under PEG-induced osmotic stress. These findings provide a basis for future functional studies and breeding applications of McYABBY genes in bitter gourd.