W233
A Tonoplast Sugar Transporter Mediates Sugar Accumulation in Dessert Watermelon (Citrullus lanatus) Fruit

Date: Sunday, January 15, 2017
Time: 4:40 PM
Room: Pacific Salon 4-5 (2nd Floor)
Yi Ren , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Jie Zhang , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Shaogui Guo , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Hongju He , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Honghe Sun , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Shouwei Tian , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Guoyi Gong , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Haiying Zhang , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
Yong Xu , National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
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Domestication of watermelon fruit was associated with the evolvement of the dessert watermelon, which accumulates large quantities of sugars, mainly sucrose. Sugar accumulates in the watermelon fruit cells vacuoles in a yet unknown molecular mechanism. We sequenced 96 RILs, derived from crossing a high sugar content cultivar with a low sugar content accession, to create an ultrahigh-density SNP map. The fine mapping narrowed previously described major sugar content QTL on chromosome 2, to a 797.4 Kb segment that includes only 20 genes. One of these genes was annotated as Tonoplast Sugar Transport (ClTST2) gene and we show that its protein product is located in the vacuolar membrane of watermelon fruit cells and is responsible for the uptake of sucrose, fructose and glucose into the vacuoles. The expression of ClTST2 is highly correlated with watermelon fruit sugar accumulation. Functional analyses of the ClTST2 promoter region identified a SNP in a SUSIBA2 transcription factor recognition site, located in a SURE (sugar responsive) element.We found that a watermelon SUSIBA2-like, termed SUSIWM1, binds to domestication SURE cis element to active ClTST2 expression. Revealing the identity and the role of ClTST2 in watermelon fruit sugar accumulation and the mechanism by which its activity is regulated, creates new tools to increase sugar sink strength in watermelon and possibly in other fruits.
Back to: Cucurbit Genomics
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