Translational Control of RuBPCase Gene Expression in Amaranth

浆果9316806光形态发生是对光反应的生长发育现象，为研究环境刺激对基因表达的调控提供了有价值的实验系统。在苋菜幼苗中，光协同调节核酮糖1，5-二磷酸羧化酶(RuBPCase)的大亚基(LSU)和小亚基(SSU)基因的表达，RuBPCase是光合作用固碳的主要酶。虽然RuBPCase基因表达的长期变化是在mRNA积累水平上受到光的调控，但RuBPCase基因表达的快速变化是在两个翻译水平上诱导的。当暗培养的幼苗转入光照(光移)时，RuBPCase的合成在翻译起始水平上被迅速诱导，而当光照生长的幼苗转入黑暗时，RuBPCase的合成在翻译延伸水平上被迅速阻止。我们建议在这两个翻译步骤中研究叶绿体编码的LSU和核编码的SSU的调节。通过对多聚体相关蛋白的分析、与RuBPCase mRNAs相关的蛋白质的分析，以及对RNA序列和相关因子的体内和体外分析，将研究光生长、暗生长和光移幼苗中翻译启动的调节。将通过分析核糖体的分布和核糖体停顿的位置，分析同源翻译径流提取物中的伸长区块，以及多聚体相关蛋白的分析，来研究光生长和暗移位幼苗翻译伸长的调节。拟议的研究将为在翻译水平上协调调控核和叶绿体编码基因的表达提供新的见解。在植物中，光是调节生长的环境信号。对植物光调节反应的研究对于确定控制植物发育的因素如何对环境刺激(如光)做出反应是重要的。为了开始了解这是如何发生的，我们将研究植物基因的光控制，这些基因负责在籽粒植物苋菜中形成二氧化碳固定酶。将进行实验，以观察光照如何控制植物中酶的数量的快速变化。这似乎发生在信使RNA的水平上，信使RNA由DNA产生，然后被翻译成植物二氧化碳固定蛋白。这一研究结果将为光在光合作用中的遗传控制提供独特的视角。此外，我们与Amaranth的基础研究将有助于将该植物发展为一种重要的粮食生产和工业作物。***

Berry 9316806 Photomorphogenesis, the phenomenon of growth and development in response to light, provides a valuable experimental system to study the control of gene expression by environmental stimuli. In Amaranth seedlings, light coordinately regulates the expression of genes encoding the large subunit (LSU) and small subunit (SSU) of ribulose 1,5-bisphosphate carboxylase (RuBPCase), a principle enzyme in photosynthetic carbon fixation. While long-term changes in RuBPCase gene expression are regulated by light at the level of mRNA accumulation, very rapid changes in RuBPCase gene expression are induced at two translational levels. RuBPCase synthesis is rapidly induced at the level of translation initiation when dark- grown seedlings are transferred to light (light-shift), and is rapidly blocked at the level of translation elongation when light- grown seedlings are transferred to darkness. We propose to investigate the regulation of chloroplast-encoded LSU and nuclear- encoded SSU at these two translation steps. Regulation of translation initiation will be investigated in light-grown, dark- grown, and light-shifted seedlings by analysis of polysome- associated proteins, analysis of proteins that associate with RuBPCase mRNAs, and by in vivo and in vitro analysis of RNA sequences and associated factors. Regulation of translation elongation will be studied in light-grown and dark-shifted seedlings by analysis of ribosome distribution and sites of ribosome pausing, analysis of the elongation block in homologous translation runoff extracts, and analysis of polysome-associated proteins. The investigations proposed will provide new insights into coordinate regulation of expression of nuclear- and plastid- encoded genes at the translational level. %%% In plants, light serves as an environmental signal that regulates development. Investigations into light-regulated responses in plants are important in determining how factors that control plant development respo nd to environmental stimuli, such as light. To begin to understand how this occurs, we will study light-control of plant genes responsible for forming the carbon dioxide fixation enzyme in Amaranth, a grain plant. Experiments will be performed to observe how light exposure can control rapid changes in the amounts of the enzyme in the plant. This appears to happen at the level of messenger RNA, which is produced from DNA and afterwards is translated into the plant carbon dioxide fixation protein. Results of this research will provide unique perspectives about light on the genetic control in photosynthesis. In addition, our basic research with Amaranth will contribute to the development of the plant as an important agricultural crop for food production and for industry. ***