水稻CIC1蛋白调节光合作用低温适应的分子机理研究

Low temperature is one of the major environmental factors limiting photosynthetic activities and yield of rice. Numerous reports indicate that chilling reduces photosynthetic function of rice seedlings, but its molecular mechanism is not clear. To study the mechanism of chilling sensitivity of rice plants, we obtained a chilling-induced chlorotic mutant from the rice mutant library. We isolated the gene by map-based cloning. The CIC1 protein was found to be localized in the chloroplast. Phenotypic and biochemical analyses revealed that cic1 mutant developed chlorotic leaves, showed reduced photosynthetic activities and accumulation of chloroplast-encoded proteins under chilling stress. In order to investigate the molecular mechanism of CIC1 protein in the chloroplast gene expression and photosynthesis of rice seedlings under chilling stress, phenotype of cic1 mutant, functional characterization of CIC1 gene expression and the associated proteins of CIC1 will be studied.

低温冷害是影响水稻光合功能和产量的重要环境胁迫因素之一，大量研究表明，低温导致水稻光合作用功能下降，但其分子机理一直不清楚。为了研究水稻低温敏感的分子机理，我们从水稻突变体库中筛选到一个低温黄化的突变体，图位克隆了突变基因CIC1，并证实CIC1蛋白定位于叶绿体。前期研究显示，CIC1基因突变引起低温下水稻叶片黄化，光合活性下降，叶绿体基因编码蛋白积累减少。本项目在已有工作的基础上，通过分析水稻cic1突变体低温下的表型和功能，研究CIC1蛋白在低温下水稻叶绿体基因表达和光合系统功能损伤中的作用，找寻和CIC1蛋白功能相关的其它调控因子，阐明CIC1蛋白参与低温下叶绿体基因表达和光合作用调控的分子机制。

冷害是影响水稻光合功能和产量的重要环境胁迫因素之一。在低温下如何维持光合系统的正常活性对于植物的生长发育具有重要的意义。我们从粳稻日本晴EMS诱变库中筛选到一个低温敏感突变体cic1，并对其低温下的功能进行了研究。与野生型相比，低温下cic1突变体叶片黄化、叶绿体发育异常、PS II和PSI活性降低、光合碳同化速率下降、光合蛋白积累减少、活性氧清除系统活性增强。研究结果表明，低温下突变体叶绿体编码基因的转录受到了严重抑制。突变体CIC1蛋白低温下失去与psbC，psbD mRNA的亲和力。进一步研究显示，CIC1蛋白通过与叶绿体转录因子sigma5相互作用，保护低温下叶绿体基因的正常表达。

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