Figure 6.

Regulation of ClTST2 and SUSIWM1. A, ChIP analysis of SUSIWM1 recruitment to the ClTST2 promoter W box3, which contains the −1,368 SNP (A/C) in a SURE element. The results are expressed as means ± sd. B, Changes in fruit sugar content (Brix) and color 3 d after injection of 1 mL 10% Suc into 10 DAP immature watermelon fruit. C, Relative level of SUSIWM1 mRNA after treatment with Suc. D, Proposed model for regulation of ClTST2 by SUSIWM1 based on RNA-seq transcriptome data. Suc induces the expression of SUSIWM1, which up-regulates ClTST2 in cultivar sweet 97103 fruit flesh, while transcription of ClTST2 is repressed during all stages of fruit maturation in low-sugar-content tissues such as PI296341-FR fruit and 97103 fruit rind.