Genome-wide identification of the GLK transcription factor family in melon and its expression analysis under biotic and abiotic stresses

This study systematically identifies and characterizes the <i>GLK</i> gene family in melon (<i>Cucumis melo</i>), identifying 49 <i>GLK</i> genes within the melon genome, which are subsequently named <i>CmGLK1</i> to <i>CmGLK49</i> based on their chromosomal locations. The <i>CmGLK</i> family members exhibit significant variation in physicochemical properties, including amino acid length, molecular weight, and isoelectric point. Phylogenetic analysis classified the <i>CmGLK</i> genes into six groups (I-VI), demonstrating a high degree of conservation of <i>GLK</i> genes across melon, cucumber, and watermelon. Motif and domain analyses indicate that all <i>CmGLK</i> family members possess the characteristic <i>GLK</i> transcription factor domain. Moreover, genes within the same phylogenetic group display similar protein motifs and gene structures, suggesting that these genes may have a common function in regulating plant growth and development. Chromosomal localization reveals that <i>CmGLK</i> genes are unevenly distributed across 12 chromosomes, with nine pairs of segmental duplications and one pair of tandem repeats, indicating that gene duplication likely plays a key role in the expansion of this gene family. Additionally, <i>GLK</i> homologs were identified between melon and <i>Arabidopsis thaliana</i>, <i>Oryza sativa</i>, <i>Cucumis sativus</i>, and <i>Citrullus lanatus</i>, with the highest homology found between melon and cucumber, as well as melon and watermelon. <i>Cis</i>-regulatory element analysis of <i>CmGLK</i> promoters reveals a high abundance of elements associated with light response, hormone regulation, and stress responses, suggesting that the <i>CmGLK</i> family may be involved in the regulation of melon growth, development, and environmental stress responses. Expression profiling shows that <i>CmGLK</i> genes are expressed in a tissue-specific manner, with the highest expression levels found in the root, stem, and leaf tissues. Further Quantitative fluorescence analysis reveals that several <i>CmGLK</i> family members exhibit significant expression changes under <i>Fusarium</i> wilt and drought stress, suggesting their potential involvement in melon's stress response mechanisms. This study provides a comprehensive analysis of the structure, evolution, and stress-responsive expression of the <i>CmGLK</i> gene family. Our findings offer new insights into the potential molecular mechanisms of melon's stress adaptation and highlight candidate <i>CmGLK</i> genes for future functional studies aimed at improving disease resistance.