Interplay between differentially expressed enzymes contributes to light color acclimation in marine Synechococcus-猫眼课题宝

DOI：

10.1073/pnas.1810491116

发表时间：

2019-03

期刊：

Proceedings of the National Academy of Sciences

影响因子：

--

通讯作者：

中科院分区：

其他

文献类型：

--

作者：

Joseph E. Sanfilippo;Adam A. Nguyen;L. Garczarek;J. Karty;S. Pokhrel;Johann A Strnat;F. Partensky;W. Schluchter;D. Kehoe

海洋浮游植物负责地球上近一半的初级生产力，而微蓝细菌聚球藻贡献了这一总数的16%。聚球藻菌株通过在不同的光色生态位中使用不同的发色团进行光合捕光来优化它们的适应性。许多聚球藻属菌株使用色驯化来调节发色团组成以适应环境蓝光与绿色光的比率。我们确定，两个发色团附着酶，MpeY和MpeZ之间的相互作用，发挥了作用，在基因表达水平的色驯化。这两种酶将不同发色团连接到同一残基的独特能力使它们可能用于荧光成像技术中该残基的差异标记。海洋聚球藻是一种重要的蓝细菌类群，其光合捕光色素的多样性决定了其在不同光环境中的生长。许多聚球藻菌株使用一种称为色驯化的过程来优化其捕光复合物中两种发色团，吸收绿光的藻红胆素（PEB）和吸收蓝光的藻胆素（PUB）的比例。一个完整的机制，了解如何聚球藻细胞调整其PEB的PUB比例在色驯化尚未获得。在这里，我们表明，两种酶命名MpeY和MpeZ控制不同的PEB和PUB共价连接到相同的半胱氨酸残基之间的相互作用。MpeY在绿色光中将PEB附着到捕光蛋白MpeA上，而MpeZ在蓝光中将PUB附着到MpeA上。我们证明了mpeY与mpeZ mRNA的比率决定了是否附着PEB或PUB。另外，仅编码MpeY或MpeZ的菌株不适应。对从地球仪分离的聚球藻菌株的检查表明，这里揭示的MpeY和MpeZ之间的相互作用是全球海洋聚球藻颜色驯化的关键特征。

Significance Marine phytoplankton are responsible for nearly half of the primary productivity on Earth, and the picocyanobacterium Synechococcus contributes up to 16% of this total. Synechococcus strains optimize their fitness by using different chromophores for photosynthetic light-harvesting in different light color niches. Many Synechococcus strains use chromatic acclimation to adjust chromophore composition to ambient blue to green light ratios. We determined that interplay between two chromophore attachment enzymes, MpeY and MpeZ, plays a role in chromatic acclimation at the level of gene expression. The unique ability of these two enzymes to attach different chromophores to the same residue makes them potentially useful for differential labeling of that residue for fluorescence-imaging technologies. Marine Synechococcus, a globally important group of cyanobacteria, thrives in various light niches in part due to its varied photosynthetic light-harvesting pigments. Many Synechococcus strains use a process known as chromatic acclimation to optimize the ratio of two chromophores, green-light–absorbing phycoerythrobilin (PEB) and blue-light–absorbing phycourobilin (PUB), within their light-harvesting complexes. A full mechanistic understanding of how Synechococcus cells tune their PEB to PUB ratio during chromatic acclimation has not yet been obtained. Here, we show that interplay between two enzymes named MpeY and MpeZ controls differential PEB and PUB covalent attachment to the same cysteine residue. MpeY attaches PEB to the light-harvesting protein MpeA in green light, while MpeZ attaches PUB to MpeA in blue light. We demonstrate that the ratio of mpeY to mpeZ mRNA determines if PEB or PUB is attached. Additionally, strains encoding only MpeY or MpeZ do not acclimate. Examination of strains of Synechococcus isolated from across the globe indicates that the interplay between MpeY and MpeZ uncovered here is a critical feature of chromatic acclimation for marine Synechococcus worldwide.