Abstract
The flesh color of oriental melons is an important commercial trait that affects consumer preferences. To explore the mechanisms underlying the flesh color formation and regulation during fruit ripening, carotenoid-targeted metabolomic and RNA-seq analysis were conducted between white-fleshed (WF) and orange-fleshed (OF) oriental melon cultivars at different stages. The carotenoid-targeted metabolomic analysis indicated that β-carotene was the major metabolite that caused differences in flesh color between the two cultivars. Additionally, through KEGG pathway enrichment and weighted gene co-expression network (WGCNA) analysis, metabolic pathways and related transcription factors that are associated with carotenoid metabolism were selected and transcriptome data was verified using RT-qPCR. Finally, the yeast one hybrid and luciferase activity showed that the transcription factor CmWRKY49 could directly bind to the CmPSY1 promoter to activate its expression in the ‘OF’ cultivar. Transient overexpression of CmWRKY49 in ‘OF’ cultivar increased the β-carotene content, while the β-carotene content decreased when it was silenced in the same cultivar. This study provides insights into the underlying regulatory network of carotenoid metabolism in oriental melon fruit.
