Geographic Mapping for sugar and nitrogen compands and their transporters

本文研究了水稻对糖的吸收和运输。种子萌发过程中的胚芽。以水稻胚芽为材料，研究了外源糖对水稻胚芽内源糖水平、淀粉粒积累和水稻蔗糖转运蛋白(OsSUT1)基因表达的影响。由于胚胎摄取了糖，维管束周围的细胞中显著积累了淀粉颗粒，这表明被摄取的糖被瞬时转化为淀粉。在筒仓中检测到OsSUT1的mRNA，表明其定位于韧皮部伴生细胞。此外，Northern印迹和原位杂交分析表明，在糖饥饿条件下的胚胎中没有检测到OsSUT1的表达，但随着内源糖水平的增加，OsSUT1的表达增强。总体结果表明，伴随细胞特异性蔗糖转运蛋白OsSUT1的表达受内源糖状态和光照的调节。本研究旨在研究水稻单糖转运蛋白基因的克隆和功能。0sMST1-3(水稻单糖转运体1-3)有两组推测的6个跨膜区，中间有一个长长的亲水区。OsMST3蛋白在酿酒酵母中的异源表达表明，OsMST3对一些单糖具有转运活性，并具有能量依赖性的H+共转运方式。Northern杂交和原位杂交分析表明，OsMST3mRNA在叶片、叶鞘、愈伤组织和根中均有表达，尤其是在木质部和根的厚壁组织细胞中均有表达。这些结果表明，OsMST3参与了细胞增厚阶段细胞壁合成所需单糖的积累。

We investigated sugar uptake and transport in rice (Oryza sativa L.) embryo during grain germination. Endogenous sugar levels, accumulation of starch granules and gene expression of a rice sucrose transporter (OsSUT1) were examined using rice embryos germinated with or without exogenous sugar supply. Starch granules remarkably accumulated in the cells around vascular bundles, as a consequence of the sugar taken up by the embryos, indicating that the taken up sugars are transiently converted into starch. In silo detection for OsSUT1 mRNA indicated its localization in the phloem companion cells. Furthermore, northern blot and in situ hybridization analyses showed that OsSUT1 expression is not detectable in embryos subjected to sugar starvation conditions while its expression is enhanced by an increased endogenous sugar level. Overall results indicate that the expression of companion cell-specific sucrose transporter, OsSUT1 is regulated by the endogenous sugar status as well as light exposure.This study examines the cloning and characterization of monosaccharide transporter cDNAs in rice. The 0sMST1-3 (Oryza sativa monosaccharide transporter 1-3) has two sets of putative six transmembrane domains separated by a central long hydrophilic region. Heterologous expression of the OsMST3 protein in yeast Saccharomyces cerevisiae revealed that OsMST3 has transport activity for some monosaccharides and an energy-dependent H+ co-transport manner. Northern blot and in situ hybridization analysis showed that OsMST3 mRNA is detectable in leaf blade, leaf sheath, callus and root, especially the xylem as well as in sclerenchyma cells in root. These results suggested that OsMST3 is involved in the accumulation of monosaccharides required for cell wall synthesis at the stage of cell thickness.