Katz, Ehud , Esumi, Tomoya , Fon, Mario , Nakano, Ryohei , Sadka, Avi , Phinney, Brett S. , Blumwald, Eduardo .
Fruit sugar transport and sugar homeostasis: Identification, gene expression and localization analysis of citrus juice sac cell vacuolar sugar transporters and identification of the citrus fruit proteome.
The sugar content of citrus fruit juice cells is a key determinant of citrus fruit quality. Fruit sugar content change during development and greatly influence the total soluble solids (TSS) of the fruit. The TSS, together with the total fruit acidity, will determine whether the fruit can be marketed. Total fruit sugar content is determined by sugar transport (accumulated in the vacuole) and metabolism (mostly cytosolic). To gain insights on the mechanisms regulating these processes we 1) isolated sugar transporters from citrus fruit juice cells and 2) characterized the juice cells proteome. The citrus ESTs database contains 114 ESTs encoding sugar transporters. We focused on two ESTs encoding sequences that are similar to previously identified putative vacuolar sugar transporters. Two full length cDNAs and genomic sequences have been obtained and analyzed. The predicted structures of these two putative vacuolar sugar transporters from citrus juice cells showed proteins comprising twelve transmembrane domains and a large central hydrophilic region. The expression of these genes increased during development and correlated well with sugar accumulation in the fruit. Heterologous expression of GFP-fused gene constructs in yeast revealed that both are localized to the tonoplast. In addition, we took a proteomic approach using LC-MS/MS analyses of membranes and soluble enriched fractions from mature citrus juice cells and searched against citrus ESTs and NCBInr databases to identify changes in juice cells. So far, we identified ca. 1400 proteins including several sugar transporters and key proteins acting in major metabolic pathways affecting sugars metabolism and homeostasis, citrate cycle, signaling, transport, processing, vesicular trafficking and others.
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1 - University of California, Plant Sciences Department, Plant Reproductive Biology, Mail Stop 5, Extension Center Drive, One Shields Ave., Davis, CA, 95616, USA
2 - Okayama University, Okayama City 700-8530 Japan, Department of Agriculture
3 - ARO, The Volcani Center, 50250 Bet Dagan, Israel, Department of Fruit Tree Species
4 - University of California, Genome Center, One Shields Ave., Davis, CA, 95616, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM