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Title: Interplay between differentially expressed enzymes contributes to light color acclimation in marine Synechococcus

MarineSynechococcus, a globally important group of cyanobacteria, thrives in various light niches in part due to its varied photosynthetic light-harvesting pigments. ManySynechococcusstrains 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 howSynechococcuscells 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 ofmpeYtompeZmRNA determines if PEB or PUB is attached. Additionally, strains encoding only MpeY or MpeZ do not acclimate. Examination of strains ofSynechococcusisolated from across the globe indicates that the interplay between MpeY and MpeZ uncovered here is a critical feature of chromatic acclimation for marineSynechococcusworldwide.

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Proceedings of the National Academy of Sciences
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p. 6457-6462
Proceedings of the National Academy of Sciences
Sponsoring Org:
National Science Foundation
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