研究表明拟南芥中的单糖转运（OsTMTs）促进了糖在液泡中的区域化分布，但人们对于单糖转运在其它作物中的作用却不清楚。韩国Kyung Hee大学的Jung-Il Cho和来自苏黎世大学及另外两所大学的同事开展了一项研究，他们对水稻中OsTMT1和OsTMT2的表达和功能进行了考查。
绿色荧光蛋白（GFP）常用于亚细胞定位，它可以区分OsTMT1和OsTMT2。这些研究人员发现单糖转运发生在液泡膜内，同时反转录PCR实验也表明，维管束鞘细胞中同时含有OsTMT1 和OsTMT2，而维管薄壁细胞和伴细胞中则分别只含有OsTMT1 和OsTMT2。研究人员还研究了转基因突变拟南芥的液泡中葡萄糖的转运能力，结果表明OsTMTs也能对葡萄糖进行转运。(生物谷Bioon.com)
生物谷推荐原文出处：
New Phytologist 10.1111/j.1469-8137.2010.03194.x
Expression analysis and functional characterization of the monosaccharide transporters, OsTMTs, involving vacuolar sugar transport in rice (Oryza sativa)
Jung-Il Cho 1 , Bo Burla 2,3 , Dae-Woo Lee 1 , Nayeon Ryoo 1 , Soon-Kwan Hong 4 , Hyun-Bi Kim 1 , Joon-Seob Eom 1 , Sang-Bong Choi 5 , Man-Ho Cho 1 , Seong Hee Bhoo 1 , Tae-Ryong Hahn 1 , H. Ekkehard Neuhaus 6 , Enrico Martinoia 2,3 and Jong-Seong Jeon 1,7
1 Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 446-701, Korea ; 2 Institute of Plant Biology, University Zurich, CH–8008 Zurich, Switzerland ; 3 POSTECH-UZH Global Research Laboratory, Division of Molecular Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea ; 4 Department of Plant Biotechnology, Kangwon National University, Chuncheon 200-701, Korea ; 5 Division of Bioscience and Bioinformatics, Myongji University, Yongin 449-728, Korea ; 6 Plant Physiology, University of Kaiserslautern, D–67653 Kaiserslautern, Germany ; 7 Crop Biotech Institute, Kyung Hee University, Yongin 446-701, Korea
ABSTRACT
In Arabidopsis, the compartmentation of sugars into vacuoles is known to be facilitated by sugar transporters. However, vacuolar sugar transporters have not been studied in detail in other plant species.
To characterize the rice (Oryza sativa) tonoplast monosaccharide transporters, OsTMT1 and OsTMT2, we analysed their subcellular localization using green fluorescent protein (GFP) and expression patterns using reverse-transcription polymerase chain reaction (RT-PCR), performed histochemical β-glucuronidase (GUS) assay and in situ hybridization analysis, and assessed sugar transport ability using isolated vacuoles.
Expression of OsTMT–GFP fusion protein in rice and Arabidopsis revealed that the OsTMTs localize at the tonoplast. Analyses of OsTMT promoter-GUS transgenic rice indicated that OsTMT1 and OsTMT2 are highly expressed in bundle sheath cells, and in vascular parenchyma and companion cells in leaves, respectively. Both genes were found to be preferentially expressed in the vascular tissues of roots, the palea/lemma of spikelets, and in the main vascular tissues and nucellar projections on the dorsal side of the seed coats. Glucose uptake studies using vacuoles isolated from transgenic mutant Arabidopsis (tmt1-2-3) expressing OsTMT1 demonstrated that OsTMTs are capable of transporting glucose into vacuoles.
Based on expression analysis and functional characterization, our present findings suggest that the OsTMTs play a role in vacuolar glucose storage in rice.
