title: Functional characterization and expression analysis of cucumber (Cucumis sativus L.) hexose transporters, involving carbohydrate partitioning and phloem unloading in sink tissues.
abstract: Many hexose transporters (HTs) have been reported to play roles in sucrose-transporting plants. However, little information about roles of HTs in RFOs (raffinose family oligosaccharides)-transporting plants has been reported. Here, three hexose transporters (CsHT2, CsHT3, and CsHT4) were cloned from Cucumis sativus L. Heterologous expression in yeast demonstrated that CsHT3 transported glucose, galactose and mannose, with a K(m) of 131.9 μM for glucose, and CsHT4 only transported galactose, while CsHT2 was non-functional. Both CsHT3 and CsHT4 were targeted to the plasma membrane of cucumber protoplasts. Spatio-temporal expression indicated that transcript level of CsHT3 was much higher than that of CsHT2 and CsHT4 in most tissues, especially in peduncles and fruit tissues containing vascular bundles. GUS staining of CsHT3-promoter-β-glucuronidase (GUS) transgenic Arabidopsis plants revealed CsHT3 expression in tissues with high metabolic turnover, suggesting that CsHT3 is involved in sugar competition among different sink organs during plant development. The transcript levels of CsHT3 and cell wall invertase genes increased in peduncles and fruit tissues along with cucumber fruit enlargement, and CsHT3 localized to phloem tissues by immunohistochemical localization; These results suggest that CsHT3 probably plays an important role in apoplastic phloem unloading of cucumber fruit.
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,; Huazhong Agricultural University, Wuhan 430070, China. Electronic address: angeldream520@126.com.
authors.forename: Jin-Tao
authors.initials: JT
authors.lastname: Cheng
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,. Electronic address: 978602801@qq.com.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,. Electronic address: 574476853@qq.com.
authors.forename: Feng-Zhen
authors.initials: FZ
authors.lastname: Yao
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,. Electronic address: nannanshan@163.com.
authors.forename: Nan
authors.initials: N
authors.lastname: Shan
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,. Electronic address: 784881129@qq.com.
authors.forename: Ya-Hui
authors.initials: YH
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,. Electronic address: zhangzx@cau.edu.cn.
authors.forename: Zhen-Xian
authors.initials: ZX
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China,. Electronic address: sui-office@cau.edu.cn.
authors.forename: Xiao-Lei
authors.initials: XL
authors.lastname: Sui
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D050260:Carbohydrate Metabolism; D002473:Cell Wall / Q000201:enzymology; D018553:Cucumis sativus / Q000235:genetics / Q000378:metabolism*; D005638:Fruit / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D052585:Phloem / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011523:Protoplasts; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins; D043324:beta-Fructofuranosidase
keywords: Cell wall invertase; Cucumber (Cucumis sativus L.); Fruit; Hexose transporter; Phloem unloading