Genome-Wide Identification of the CmTIFY Gene Family and Analysis of Its Expression Patterns under Cold Stress (Cucumis melo L.)

Plant-specific TIFY [TIF(F/Y)XG] transcription factors are critical for regulating plant stress responses. However, the CmTIFY gene family members in melon and their low-temperature response remain uncharacterized. Here, we identified 15 CmTIFY genes in melon, classified into TIFY, JAZ, ZML, and PPD subfamilies, distributed on 8 chromosomes with conserved gene structures and motifs. Phylogenetic analysis showed closer homology of CmTIFY proteins to cucumber homologs. Promoter cis-acting elements associated with hormone and abiotic stress responses indicated their roles in growth and stress adaptation. Analysis of tissue-specific gene expression patterns detected the highest levels of CmJAZ1, CmJAZ4 and CmJAZ8 mRNAs in six tissues consisting of the roots, stems, and leaves. CmJAZ2 and CmJAZ3 were mainly expressed in the vegetative tissues. In contrast, CmJAZ5 was predominantly expressed in the stamens and ovaries, thus making a major contribution to the growth and reproduction of melons. RT-qPCR results demonstrated distinct low-temperature responses: CmTIFY1, CmJAZ5, and CmZML1 were down-regulated, while CmJAZ1 and CmJAZ6 were up-regulated in leaves. This study provides a theoretical basis and genetic resources for cold-resistant melon molecular breeding, facilitating yield and stress resistance improvement.