Genome-wide Identification and Expression of the SMXL Gene Family in Cucumis melo

Purpose To identify and analyze the suppressor of more axillary growth 2-like (SMXL) gene family in melon (Cucumis melo), providing a basis for further study of the biological functions of SMXL genes in melon.

Methods The melon SMXL gene family was identified by bioinformatics methods, and the physicochemical properties, structure and function, collinearity, protein structure, promoter cis-acting elements and expression patterns of the family members were analyzed.

Results A total of 15 CmSMXL genes in melon were identified, classifying into five subfamilies (I-V), with subfamily V being the largest and most species-specific. The upstream promoter region of CmSMXLs contained abundant cis-elements related to light signaling, hormones, and drought response, etc. Most SMXL proteins were predicted to localize in chloroplasts, and CmSMXL7, CmSMXL14, and CmSMXL15 showing high expression in leaves, suggesting photosynthetic roles. Under abiotic stresses (cold, salt, hormones), the expression levels of CmSMXL1, CmSMXL3, CmSMXL6, CmSMXL8, and CmSMXL10 exhibited significant changes. CmSMXL10 and CmSMXL12 responded to powdery mildew infection, while CmSMXL3 and CmSMXL6 expression correlated with Fusarium wilt resistance.

Conclusion SMXL genes involved in stress responses are identified in melon.