Signal Transduction Mechanisms Controlling Chromatic Adaptation

本研究探讨了控制细菌光反应的信号转导机制。它旨在揭示蓝藻Fremyella diplosiphon如何感知和响应光的颜色变化。这个过程被称为“互补色适应”（CCA），涉及这种光合生物的捕光触角的大量再合成，导致完全的颜色变化。这种可逆的适应过程允许细胞有效地利用环境中的主要光波长进行光合作用。CCA由两条光响应途径控制，这两条途径介导许多基因转录的变化。Rca途径似乎是一个复杂的磷酸化继电器，控制红色和绿色光诱导的基因的表达，并包含三个已知的组件，光敏色素样感光器和两个响应调节器。Cgi途径仅控制绿色光诱导的基因。该途径中的任何组分都未被分离。Rca和Cgi系统可以通过OmpR样控制机制整合在称为“R盒”的DNA序列处。这些研究将回答有关CCA调节机制的基本问题。他们将确定（i）红光如何通过缺失和连接子扫描分析、蛋白结合和足迹研究以及CCA转录因子的纯化来增加pcyA和cpc 2表达水平;（ii）Cgi和Rca系统如何通过启动子和R盒缺失分析来调节cpeCDESTR表达;以及（iii）通过转座子诱变和分析推定的cgi突变体来确定哪些组分构成Cgi系统。更广泛的影响包括增加对光合物种如何适应光线的理解，以及对科学中代表性不足的群体成员的培训。

This research investigates signal transduction mechanisms controlling light responses in bacteria. It seeks to uncover how the cyanobacterium Fremyella diplosiphon senses and responds to changes in light color. This process, called "complementary chromatic adaptation" (CCA), involves massive resynthesis of this photosynthetic organism's light harvesting antennae, resulting in a complete color change. This reversible acclimation process allows cells to efficiently use the predominant light wavelength(s) in the environment for photosynthesis. CCA is controlled by two light-responsive pathways that mediate changes in transcription of many genes. The Rca pathway appears to be a complex phosphorelay that controls the expression of red and green light-induced genes and contains three known components, a phytochrome-like photoreceptor and two response regulators. The Cgi pathway controls only green light induced genes. None of the components in this pathway have been isolated. The Rca and Cgi systems may integrate at DNA sequences called "R Boxes" through an OmpR-like control mechanism. These studies will answer fundamental questions concerning the mechanism of CCA regulation. They will determine (i) how red light increases pcyA and cpc2 expression levels through deletion and linker scanning analyses, protein binding and footprinting studies, and purification of CCA transcription factors (ii) how the Cgi and Rca systems regulate cpeCDESTR expression through promoter and R Box deletion analysis and (iii) what components make up the Cgi system by transposon mutagenesis and analysis of putative cgi mutants. Broader impacts include increased understanding of how photosynthetic species acclimate to light and training of members of underrepresented groups in science.