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Molecular mechanisum of starch metabolism in the leaf sheaths and culms of rice plants

水稻叶鞘和秆淀粉代谢的分子机制

基本信息

批准号：
15580016
负责人：
HIROSE Tatsuro
金额：
$ 2.43万
依托单位：
National Agriculture Research Organization
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15580016/
关键词：
rice leaf sheath starch gene expression enzyme 稈分子生物学

项目摘要

To elucidate the molecular mechanisms of the accumulation and the degradation of starch in the leaf sheaths and culms of rice plants (Oryza sativa L.), a comprehensive expression pro filing of the genes potentially involved in starch metabolism was conducted, and the following results were obtained.1.The enzyme activities of starch synthesizing enzymes, ADP-glucose pyrophosphorylase, starch synthase and branching enzyme in leaf sheaths were higher in the leaf sheaths before heading than in those after heading, which mirrored the starch content. The three enzymes are shown to be encoded by 20 genes. And, in the leaf sheaths, it was observed that AGPL1 and AGPS1 for ADP-glucose pyrophosphorylase, SSI,SSIIb, SSIIIb and GBSSII for starch synthase and BEIIa for branching enzymes are predominantly expressed. These genes, besides the leaf sheaths, are expressed at relatively high levels in the vegetative tissues such as elongating leaf blades, but at very low levels in the endosperm where other members of the gene families of each enzyme are predominantly expressed.2.In the leaf sheaths, GPT2,one of the two genes encoding plastidial glucose-6-phosphate translocator was highly expressed, and the temporal pattern of its transcript level was very similar to that of starch synthesizing enzyme genes such as AGPL1. This implies that import of the substrate for starch synthesis as well as starch synthesis could be under coordinated transcriptional regulation.3.The activity of alpha-amylase in the leaf sheaths rose after heading when the starch content continued to decline. However, the transcript levels of the ten genes for alpha-amylase did not show any obvious change, suggesting that the rise in the enzyme activity is under post-transcriptional control(s).

为了阐明水稻(Oryza sativa L.)叶鞘和秆中淀粉积累和降解的分子机制，对可能参与淀粉代谢的基因进行了全面的表达谱分析，得到以下结果： 1.淀粉合成酶、ADP-葡萄糖焦磷酸化酶、淀粉酶的酶活性叶鞘中的合酶和分支酶在抽穗前的叶鞘中高于抽穗后的叶鞘，这反映了淀粉含量。这三种酶由 20 个基因编码。并且，在叶鞘中，观察到ADP-葡萄糖焦磷酸化酶的AGPL1和AGPS1、淀粉合酶的SSI、SSIIb、SSIIIb和GBSSII以及分支酶的BEIIa主要表达。除叶鞘外，这些基因在营养组织（例如伸长的叶片）中表达水平相对较高，但在胚乳中表达水平非常低，每种酶基因家族的其他成员主要表达。 2.在叶鞘中，编码质体葡萄糖-6-磷酸转位子的两个基因之一的 GPT2 高表达，其时间模式转录水平与淀粉合成酶基因如 AGPL1 的转录水平非常相似。这表明淀粉合成底物的输入以及淀粉合成可能受到转录调控的协调作用。3.抽穗后叶鞘中淀粉含量持续下降时,α-淀粉酶活性上升。然而，α-淀粉酶的十个基因的转录水平没有显示任何明显的变化，表明酶活性的升高是在转录后控制之下的。