Abstract：
Light perception by photoreceptors impacts plastid transcription, development, and differentiation. This photoreceptor-dependent activity suggests a mechanism for photoregulation of gene expression in the nucleus and plastid that serves to coordinate expression of critical genes of these two organelles. This coordinate expression is required for proper stoichiometric accumulation of components needed for assembly of plastids, photosynthetic light-harvesting complexes and components such as phytochromes. Chloroplast-targeted sigma factors, which function together with the plastid-encoded RNA polymerase to regulate expression of plastid-encoded genes, and nuclear-encoded plastid development factors, such as GLK1 and GLK2, are targets of phytochrome regulation. Such phytochrome-dependent functions are hypothesized to allow light-dependent regulation, and feasibly tuning, of plastid components and function in response to changes in the external environment, which directly affects photosynthesis and the potential for light-induced damage. When the size and protein composition of the light-harvesting complexes are not tuned to the external environment, imbalances in electron transport can impact the cellular redox state and cause cellular damage. We show that phytochromes specifically regulate the expression of multiple factors that function to modulate plastid transcription and, thus, provide a paradigm for coordinate expression of the nuclear and plastid genomes in response to changes in external light conditions. As phytochromes respond to changes in the prevalent wavelengths of light and light intensity, we propose that specific phytochrome-dependent molecular mechanisms are used during light-dependent signaling between the nucleus and chloroplast during photomorphogenesis to coordinate chloroplast development with plant developmental stage and the external environment.
摘要：
光感受器的光感知会影响质体转录，发展,和差异化。这种光感受器依赖性活性表明了一种在细胞核和质体中基因表达的光调节机制，该机制用于协调这两个细胞器的关键基因的表达。该坐标表达式是质体组装所需的组分的适当化学计量积累所必需的。光合捕光复合物和成分，如植物色素。叶绿体靶向σ因子，它们与质体编码的RNA聚合酶一起调节质体编码基因的表达，和核编码质体发育因子，例如GLK1和GLK2是植物色素调节的目标。假设这种植物色素依赖性功能允许光依赖性调节，和可行的调谐，质体成分和功能响应外部环境的变化，直接影响光合作用和光致损伤的可能性。当捕光复合物的大小和蛋白质组成不适应外部环境时，电子传输的不平衡会影响细胞的氧化还原状态并导致细胞损伤。我们表明，植物色素特异性调节多种因子的表达，这些因子具有调节质体转录的功能，因此，为响应外部光条件的变化而协调表达核和质体基因组提供范例。由于植物色素响应于普遍的光波长和光强度的变化，我们建议在光形态发生过程中，在细胞核和叶绿体之间的光依赖性信号传导过程中使用特定的植物色素依赖性分子机制来协调叶绿体发育与植物发育阶段和外部环境。
