Isolation and Activity Analysis of Phytoene Synthase (ClPsy1) Gene Promoter of Canary-Yellow and Golden Flesh-Color Watermelon

Watermelon (Citrullus lanatus) is an economically important cucurbit crop. Its pulp rich in antioxidant carotenoids, which confer a variety of flesh colors. ClPsy1 (Phytoene Synthase) the rate-limiting enzyme for carotenoid synthesis; however, promoter activity still unknown. In present study, sequences were isolated from four watermelon accessions: Cream Saskatchewan pale yellow (COS), canary (PI 635597), golden 192938), and red (LSW-177), all express at extremely high levels. Sequence alignment cis-element analysis disclosed six SNPs between lines COS, two (at 598th 1257th positions) caused MYC MYB binding sequence variations, respectively. To confirm gene activity, full-length deletion fragments constructed connected to β-D-glucosidase (GUS) vector transferred into tomato fruits. GUS staining was performed analyze key segment promoter. The PI 192938 exceeded that COS. fragment −1521 bp −1043 exhibited strong contained transcription factor-binding site mutation. We combined RNA-seq with qRT-PCR expression pattern factor Cla97C10G196920 found (ClMYB21) showed same trend ClPsy1, positively regulates synthesis metabolism.