CmFUL1 was potentially involved in fruit elongation in melon

Abstract Melon (Cucumis melo L.) is a fruit crop in the world; fruit size and fruit shape are major traits for melon quality. Fruit length is a crucial indicator affecting fruit size and shape, but few genes regulating this trait have been identified. Here, we identified the transcription factor CmFUL1 (FRUITFULL) as a candidate for regulating fruit length using genome-wide association analysis (GWAS) and phylogenetic analysis. CmFUL1 is mainly expressed during flower and ovary development by tissue-specific expression. Transcriptional analysis revealed that CmFUL1 expression levels exhibited a negative correlation with fruit length across diverse melon germplasm. Furthermore, functional characterization demonstrated that CmFUL1 acts as a negative regulator of fruit elongation, CR-Cmful1 mutants generated by CRISPR-Cas9 showing enhanced longitudinal fruits. This repressive role was evolutionarily conserved, as heterologous overexpression of CmFUL1 in tomato consistently inhibited fruit elongation. Collectively, the results suggested that CmFUL1 is a candidate gene involved in regulating fruit length in melon, and provided genetic resources for molecular breeding of melon.