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Molecular mechanisms of the effects of water stress on the reduction of the rate of leaf photosynthesis during senescence

水分胁迫对衰老过程中叶片光合作用速率降低影响的分子机制

基本信息

批准号：
14360010
负责人：
HIRASAWA Tadashi
金额：
$ 9.41万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Water stress enhances the reduction of the rate of leaf photosynthesis during senescence, which results in the reduction of dry matter production in crop plants under water stress. The objective of this research was undertaken to investigate molecular mechanisms of the effects of water stress on the rate of leaf photosynthesis during senescence. The followings are obtained results in the research.(1)The reduction in leaf levels of nitrogen and ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) was responsible for the significant reduction of the rate of leaf photosynthesis during senescence under water stress in rice plants.(2)The amount of cytokinins, especially trans-zeatin, transported from roots to shoot decreased significantly in rice plants under water stress and there were close correlations between the total amount of the cytokinins and the rate of leaf photosynthesis, the leaf levels of nitrogen and Rubisco.(3)Application of additional cytokinin increased the nitrogen partitioning and the level of Rubisco mRNA (rbcL and rbcS).(4)From the results mentioned above, it was suggested that cytokinins transported from roots to shoot might be included in the mechanisms of the enhancement of the reduction in the rate of leaf photosynthesis. The reduction in the cytokinins transport under water stress might cause the decreased portioning of nitrogen to leaves and the decreased Rubisco synthesis and/or might enhance the Rubisco decomposition.(5)In order to elucidate the mechanism of molecular responses to water stress, the protein kinase activities were analyzed in cucumber cotyledons subjected to water stress. It has been found that ABA and salt stress, which induce the water stress responsible,-amylase, activate a 38 kDa protein kinase in cucumber cotyledons. This result suggests that the 38kDa protein kinase may play an important role in responses to water stress.

水分胁迫加剧了衰老过程中叶片光合作用速率的降低，从而导致水分胁迫下作物干物质生产的减少。本研究旨在探讨水分胁迫影响叶片衰老过程中光合作用速率的分子机制。研究结果表明：(1)水分胁迫下水稻植株衰老过程中叶片氮素和核酮糖-1，5-二磷酸羧基/加氧酶(Rubisco)水平的降低是导致叶片光合作用速率显著降低的原因。(2)水分胁迫下水稻植株从根向地上部运输的细胞分裂素，尤其是反式玉米素的含量显著减少，细胞分裂素总量与叶片光合作用速率密切相关。(3)外源细胞分裂素提高了叶片的氮素分配和Rubisco mRNA(rbcL和rbcs)水平。(4)上述结果表明，细胞分裂素从根向地上部运输可能是促进叶片光合作用速率降低的机制之一。水分胁迫下细胞分裂素转运减少可能导致叶片氮素分配减少，Rubisco合成减少和/或可能促进Rubisco分解。(5)为了阐明水分胁迫下黄瓜子叶蛋白激酶活性的变化，阐明了水分胁迫下黄瓜子叶对水分胁迫的分子响应机制。研究发现，ABA和盐胁迫诱导了水分胁迫相关的-淀粉酶，激活了黄瓜子叶中一个38 kDa的蛋白激酶。这一结果表明，38 kDa的蛋白激酶可能在水分胁迫的应答中发挥重要作用。