title: Identification and Functional Characterization of a Tonoplast Dicarboxylate Transporter in Tomato (Solanum lycopersicum).
abstract: Acidity plays an important role in flavor and overall organoleptic quality of fruit and is mainly due to the presence of organic acids. Understanding the molecular basis of organic acid metabolism is thus of primary importance for fruit quality improvement. Here, we cloned a putative tonoplast dicarboxylate transporter gene (SlTDT) from tomato, and submitted it to the NCBI database (GenBank accession number: KC733165). SlTDT protein contained 13 putative transmembrane domainsin silicoanalysis. Confocal microscopic study using green fluorescent fusion proteins revealed that SlTDT was localized on tonoplast. The expression patterns ofSlTDTin tomato were analyzed by RT-qPCR. The results indicated thatSlTDTexpressed in leaves, roots, flowers and fruits at different ripening stages, suggestingSlTDTmay be associated with the development of different tissues. To further explore the function ofSlTDT, we constructed both overexpression and RNAi vectors and obtained transgenic tomato plants by agrobacterium-mediated method. Gas chromatography-mass spectrometer (GC-MS) analysis showed that overexpression ofSlTDTsignificantly increased malate content, and reduced citrate content in tomato fruit. By contrast, repression ofSlTDTin tomato reduced malate content of and increased citrate content. These results indicated that SlTDT played an important role in remobilization of malate and citrate in fruit vacuoles.
authors.affiliation: Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of SciencesBeijing, China; College of Life Sciences, University of Chinese Academy of SciencesBeijing, China.
authors.forename: Ruiling
authors.initials: R
authors.lastname: Liu
authors.affiliation: Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences Beijing, China.
authors.forename: Boqiang
authors.initials: B
authors.lastname: Li
authors.affiliation: Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences Beijing, China.
authors.forename: Guozheng
authors.initials: G
authors.lastname: Qin
authors.affiliation: Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences Beijing, China.
authors.forename: Zhanquan
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of SciencesBeijing, China; College of Life Sciences, University of Chinese Academy of SciencesBeijing, China.
authors.forename: Shiping
authors.initials: S
authors.lastname: Tian
keywords: RNAi; organic acid composition; overexpression; tomato; tonoplast transporters