Translational Control of RuBPCase Gene Expression

[9728547]浆果苋菜是一种双子叶的谷物植物，利用高效的c4光合作用途径。在苋菜中，编码1,5-二磷酸核酮糖（RuBPCase）大亚基（LSU，由质体编码的rbcL基因产生）和小亚基（SSU，由核编码的rbcL基因产生）的基因的表达受光照和发育过程的强烈调节。在此之前，已经有研究表明，光照变化会诱导LSU和SSU多肽的合成发生非常快速的变化，这些变化是由于翻译水平的调控。此外，rbcL和rbc mrna翻译的改变与叶片光合能力的变化有关，并且似乎发生在叶片发育的各个阶段。即将进行的研究将分析发生在rbcL mRNA 5' UTR处的光依赖性mRNA/蛋白质相互作用。两个47 kDa蛋白的光依赖性结合和慢迁移凝胶迁移复合物对加工rbcL 5'UTR序列的形成与我们观察到的光诱导活化RuBPCase LSU翻译密切相关。为了更好地理解mRNA/蛋白相互作用在调控这种质体编码的光合多肽合成中的作用，我们将对主要的47 kDa rbcL 5' UTR mRNA结合蛋白进行表征并确定其相关因子。我们将研究由光生长植物的质体提取物产生的慢迁移rbcL 5' UTR RNA结合复合物的形成和组成，以及由暗生长植物的质体提取物产生的快速迁移复合物。此外，还将确定rbcL 5' UTR长度的加工差异如何阻止或增强光依赖性蛋白结合和复合物的形成。从长远来看，从这些深入的生化研究中获得的信息将用于表征光依赖性蛋白/ RNA相互作用的动力学特性，并确定使用转基因C4 dicot系统的RNA结合蛋白的作用。这些研究将为C4苋菜和其他高等植物在翻译水平上调控光合基因表达的机制提供新的见解。在高等植物中，光既是主要的能量来源，也是调节发育的环境信号。研究植物的光调节反应对于确定控制植物发育的因子如何响应环境刺激具有重要意义。在所有生物体中，蛋白质翻译过程是整个基因表达途径中不可分割的一部分。特定mrna翻译的快速变化可能是一种适应可能影响生物体生存的突然环境变化的机制。除了为光合作用的遗传控制提供独特的视角外，这项对苋菜的基础研究将有助于其发展成为一种重要的农业作物，用于粮食生产和工业。

9728547 Berry/Gollnick Amaranth is a dicotyledonous grain plant that uses the highly efficient c4 pathway of photosynthesis. In amaranth, the expression of genes encoding the large subunit (LSU, produced from the plastid-encoded rbcL gene) and small subunit (SSU, produced from nuclear-encoded rbcS genes) of ribulose 1,5-bisphosphate (RuBPCase) is strongly regulated by light and by developmental processes. Previously, it has been shown that very rapid changes in synthesis of the LSU and SSU polypeptides are induced in response to changes in illumination, and that these changes are due to regulation at the translations/level. In addition, alterations in translation from rbcL and RbcS mRNAs are associated with changes in leaf photosynthetic capacity, and appear to occur during various stages of leaf development. The research to be conducted will analyze light-dependent mRNA/protein interactions that occur at the 5' UTR of rbcL mRNA. The light-dependent binding of two 47 kDa proteins and the formation of a slow-migrating gel mobility shift complex to processed rbcL 5'UTR sequences are tightly associated with our observations of light-induced activation of RuBPCase LSU translation. To better understand the role of mRNA/protein interactions in regulating the synthesis of this plastid-encoded photosynthetic polypeptide, the predominant 47 kDa rbcL 5' UTR mRNA binding proteins will be characterized and their associated factors identified. The formation and composition of the slow-migrating rbcL 5' UTR RNA binding complex produced by plastid extracts from light-grown plants will be investigated, as will the fast-migrating complex produced by the dark-plastid extracts. In addition, it will be determined how processing differences in the length of the rbcL 5' UTR prevent or enhance light-dependent protein binding and complex formation. In the long term, the information acquired from these in depth biochemical studies will be used to characterize the kinetic properties of the light-dependent protein/R NA interactions, and to determine the role of the RNA binding proteins using a transgenic C4 dicot system. These investigations will provide novel insights into mechanisms that regulate photosynthetic gene expression at the translational level in the C4 dicot amaranth and other higher plants. In higher plants light serves both as a primary energy source and as an environmental signal that regulates development. Investigations into light-regulated responses in plants are of fundamental importance in determining how factors controlling plant development respond to environmental stimuli. The process of protein translation is an integral part of the overall pathway of gene expression in all organisms. Rapid changes in the translation of specific mRNAs may be a mechanism for adapting to sudden environmental changes that could affect the survival of the organism. In addition to providing unique perspectives about the genetic control of photosynthesis, this basic research with amaranth will aid in its development as an agriculturally important crop for food production and for industry.