Genome-Wide Characterization and Expression Profiling of the Jacalin-Related Lectin (JRL) Gene Family Under Salt and Hormone Stresses in Melon (Cucumis melo L.)

Jacalin-related lectins (JRLs) are carbohydrate-binding proteins that play essential roles in plant growth, disease resistance, and abiotic stress responses; nevertheless, systematic genome-wide analyses of the JRL family remain limited in cucurbit crops. Here, we identified seven JRL genes in the melon (Cucumis melo L.) genome, all located on chromosomes 3 and 4, with six forming a tandem cluster on chromosome 4. All seven encoded proteins contain a conserved Jacalin domain, and two members additionally possess N-terminal C1_2 domains, indicating structural and functional divergence within the family. Phylogenetic analysis using homologs from melon, cucumber, and watermelon resolved the seven genes into five subgroups. Promoter analysis revealed multiple hormone- and stress-responsive cis-acting elements. Public transcriptome data uncovered distinct tissue-specific expression patterns: MELO3C010973 was constitutively expressed, MELO3C003821 showed root-enriched expression, and MELO3C003823 was enriched in both male and female floral organs, whereas MELO3C003822 and MELO3C003824 maintained low basal transcript levels. qRT-PCR revealed temporal expression changes under NaCl, ABA, and MeJA treatments relative to the 0-h calibrator: MELO3C003819 showed pronounced ABA-responsive expression, peaking at 12 h, MELO3C003821 showed elevated transcript levels under salt stress at 24 h, MELO3C003823 showed elevated transcript levels under MeJA and salt, and MELO3C010973 showed an early transcript increase under salt. Collectively, these results provide a foundation for functional studies of melon JRL genes and highlight MELO3C003819 and MELO3C003823 as promising salt-responsive candidates whose functions require further genetic and physiological validation.