High‐level expression of a novel chromoplast phosphate transporter ClPHT4;2 is required for flesh color development in watermelon. Issue 3 (27th October 2016)

• Record Type: Journal Article
• Authors: Zhang, Jie; Guo, Shaogui; Ren, Yi; Zhang, Haiying; Gong, Guoyi; Zhou, Ming; Wang, Guizhang; Zong, Mei; He, Hongju; Liu, Fan; Xu, Yong
• Is Part Of: New phytologist. Volume 213:Issue 3(2017)
• Page Start: 1208
• Page End: 1221
• Publication Date: 2016-10-27
• Subjects: chromoplast -- Citrullus lanatus -- flesh color -- phosphate transporter -- transcriptional regulation; Botany -- Periodicals; 580
• DOI: 10.1111/nph.14257
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: Chromoplast development plays a crucial role in controlling carotenoid content in watermelon flesh. Modern cultivated watermelons with colorful flesh are believed to originate from pale‐colored and no‐sweet progenitors. But the molecular basis of flesh color formation and regulation is poorly understood. More chromoplasts and released carotenoid globules were observed in the red‐fleshed fruit of the 97103 cultivar than in the pale‐colored fruits of the PI296341‐FR line. Transcriptome profiles of these two materials identified Cla017962, predicted as ClPHT4;2, was dramatically up‐regulated during flesh color formation. High ClPHT4;2 expression levels were closely correlated with increased flesh carotenoid contents among 198 representative watermelon accessions. Down‐regulation of ClPHT4;2 expression in transgenic watermelons reduced the fruit carotenoid accumulation. ClPHT4;2 as a function of chromoplast‐localized phosophate transporter was tested by heterologous expression into a yeast phosphate‐uptake‐defective mutant, western blotting, subcellular localization, and immunogold electron microscopy analysis. Two transcription factors, ClbZIP1 and ClbZIP2, were identified, which responded to ABA and sugar signaling to regulate ClPHT4;2 transcription only in cultivated watermelon species. Our findings suggest that elevated ClPHT4;2 gene expression is necessary for carotenoid accumulation, and may help to characterize the co‐development of flesh color and sweetness during watermelon development and domestication.