High-level expression of a novel chromoplast phosphate transporter ClPHT4;2 is required for flesh color development in watermelon.
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.
['Zhang|Jie|J|', 'Guo|Shaogui|S|', 'Ren|Yi|Y|', 'Zhang|Haiying|H|', 'Gong|Guoyi|G|', 'Zhou|Ming|M|', 'Wang|Guizhang|G|', 'Zong|Mei|M|', 'He|Hongju|H|', 'Liu|Fan|F|', 'Xu|Yong|Y|']
D000040:Abscisic Acid D002338:Carotenoids D029773:Citrullus D060146:Ecotype D005638:Fruit D018506:Gene Expression Regulation, Plant D017343:Genes, Plant D005816:Genetic Complementation Test D005947:Glucose D005998:Glycine D009154:Mutation D009943:Organophosphorus Compounds D010641:Phenotype D028061:Phosphate Transport Proteins D010858:Pigmentation D010940:Plant Proteins D030821:Plants, Genetically Modified D018087:Plastids D011401:Promoter Regions, Genetic D011485:Protein Binding D011728:Pyridones D012333:RNA, Messenger D020218:Response Elements D013347:Subcellular Fractions D013395:Sucrose D014157:Transcription Factors D014158:Transcription, Genetic
chromoplast phosphate transporter flesh color Citrullus lanatus transcriptional regulation