Two Cyanobacterial Photoreceptors Regulate Photosynthetic Light Harvesting by Sensing Teal, Green, Yellow, and Red Light
Two Cyanobacterial Photoreceptors Regulate Photosynthetic Light Harvesting by Sensing Teal, Green, Yellow, and Red Light
复制标题
两种蓝藻光感受器通过感测青色、绿色、黄色和红色光来调节光合光收集
作者：
Lisa Wiltbank;D. Kehoe
摘要许多光合细菌和非光合细菌的基因组编码许多光敏色素超家族光受体，其功能和相互作用在很大程度上尚不清楚。蓝细菌基因组编码大量的光敏色素超家族成员，称为蓝细菌色素。它们具有不同的光颜色感知能力，它们的功能和相互作用才刚刚开始被理解。这些功能的最佳特征之一是在蓝藻Fremyella diplosiphon的光合捕光天线组合物的调节由蓝细菌色素RcaE响应于红色和绿色光，被称为色驯化的过程。我们已经确定了一种新的蓝细菌色素命名为DpxA，最大限度地感知青色（吸收最大值，494 nm）和黄色（吸收最大值，568 nm）光，并抑制积累的一个关键的捕光蛋白称为藻红蛋白，这也是由RcaE在色驯化过程中调节。与RcaE一样，DpxA是一种双组分系统激酶，尽管这两种光感受器可以通过不同的信号通路影响藻红蛋白的表达。DpxA对蓝绿色和黄色光的峰值响应在绿色光谱区域中提供高度精细的颜色辨别，这为蓝细菌中的光合光捕获提供了重要波长。这些结果重新定义了蓝细菌的色驯化，并表明蓝细菌色素可以协调地赋予复杂的光的颜色传感整个可见光谱，以调节重要的光合驯化过程。蓝藻基因组编码的大量蓝藻色素光感受器表明，这些生物体能够非常复杂的光的颜色传感和响应，但很少有人知道他们的功能和相互作用。我们的工作揭示了以前未描述的合作，两个感光器具有非常不同的光颜色感应能力，共同调节一个重要的光合捕光蛋白，以响应蓝绿色，绿色，黄色和红色光。其他已经被证明在功能上相互作用的蓝细菌色素可以感知彼此接近的光波长，这使得很难清楚地识别它们在细胞中的生理作用。我们发现了两种具有广泛的光色感知能力和明确定义的生理作用的光感受器，这为复杂的光色感知及其调节提供了新的见解。蓝藻基因组编码的大量蓝藻色素光感受器表明，这些生物体能够非常复杂的光的颜色传感和响应，但很少有人知道他们的功能和相互作用。我们的工作揭示了以前未描述的合作，两个感光器具有非常不同的光颜色感应能力，共同调节一个重要的光合捕光蛋白，以响应蓝绿色，绿色，黄色和红色光。其他已经被证明在功能上相互作用的蓝细菌色素可以感知彼此接近的光波长，这使得很难清楚地识别它们在细胞中的生理作用。我们发现了两种具有广泛的光色感知能力和明确定义的生理作用的光感受器，这为复杂的光色感知及其调节提供了新的见解。
ABSTRACT The genomes of many photosynthetic and nonphotosynthetic bacteria encode numerous phytochrome superfamily photoreceptors whose functions and interactions are largely unknown. Cyanobacterial genomes encode particularly large numbers of phytochrome superfamily members called cyanobacteriochromes. These have diverse light color-sensing abilities, and their functions and interactions are just beginning to be understood. One of the best characterized of these functions is the regulation of photosynthetic light-harvesting antenna composition in the cyanobacterium Fremyella diplosiphon by the cyanobacteriochrome RcaE in response to red and green light, a process known as chromatic acclimation. We have identified a new cyanobacteriochrome named DpxA that maximally senses teal (absorption maximum, 494 nm) and yellow (absorption maximum, 568 nm) light and represses the accumulation of a key light-harvesting protein called phycoerythrin, which is also regulated by RcaE during chromatic acclimation. Like RcaE, DpxA is a two-component system kinase, although these two photoreceptors can influence phycoerythrin expression through different signaling pathways. The peak responsiveness of DpxA to teal and yellow light provides highly refined color discrimination in the green spectral region, which provides important wavelengths for photosynthetic light harvesting in cyanobacteria. These results redefine chromatic acclimation in cyanobacteria and demonstrate that cyanobacteriochromes can coordinately impart sophisticated light color sensing across the visible spectrum to regulate important photosynthetic acclimation processes. IMPORTANCE The large number of cyanobacteriochrome photoreceptors encoded by cyanobacterial genomes suggests that these organisms are capable of extremely complex light color sensing and responsiveness, yet little is known about their functions and interactions. Our work uncovers previously undescribed cooperation between two photoreceptors with very different light color-sensing capabilities that coregulate an important photosynthetic light-harvesting protein in response to teal, green, yellow, and red light. Other cyanobacteriochromes that have been shown to interact functionally sense wavelengths of light that are close to each other, which makes it difficult to clearly identify their physiological roles in the cell. Our finding of two photoreceptors with broad light color-sensing capabilities and clearly defined physiological roles provides new insights into complex light color sensing and its regulation. The large number of cyanobacteriochrome photoreceptors encoded by cyanobacterial genomes suggests that these organisms are capable of extremely complex light color sensing and responsiveness, yet little is known about their functions and interactions. Our work uncovers previously undescribed cooperation between two photoreceptors with very different light color-sensing capabilities that coregulate an important photosynthetic light-harvesting protein in response to teal, green, yellow, and red light. Other cyanobacteriochromes that have been shown to interact functionally sense wavelengths of light that are close to each other, which makes it difficult to clearly identify their physiological roles in the cell. Our finding of two photoreceptors with broad light color-sensing capabilities and clearly defined physiological roles provides new insights into complex light color sensing and its regulation.