Dataset Information

Adaptation to Blue Light in Marine Synechococcus Requires MpeU, an Enzyme with Similarity to Phycoerythrobilin Lyase Isomerases.

ABSTRACT: Marine Synechococcus has successfully adapted to environments with different light colors, which likely contributes to this genus being the second most abundant group of microorganisms worldwide. Populations of Synechococcus that grow in deep, blue ocean waters contain large amounts of the blue-light absorbing chromophore phycourobilin (PUB) in their light harvesting complexes (phycobilisomes). Here, we show that all Synechococcus strains adapted to blue light possess a gene called mpeU. MpeU is structurally similar to phycobilin lyases, enzymes that ligate chromophores to phycobiliproteins. Interruption of mpeU caused a reduction in PUB content, impaired phycobilisome assembly and reduced growth rate more strongly in blue than green light. When mpeU was reintroduced in the mpeU mutant background, the mpeU-less phenotype was complemented in terms of PUB content and phycobilisome content. Fluorescence spectra of mpeU mutant cells and purified phycobilisomes revealed red-shifted phycoerythrin emission peaks, likely indicating a defect in chromophore ligation to phycoerythrin-I (PE-I) or phycoerythrin-II (PE-II). Our results suggest that MpeU is a lyase-isomerase that attaches a phycoerythrobilin to a PEI or PEII subunit and isomerizes it to PUB. MpeU is therefore an important determinant in adaptation of Synechococcus spp. to capture photons in blue light environments throughout the world's oceans.

SUBMITTER: Mahmoud RM

PROVIDER: S-EPMC5318389 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Adaptation to Blue Light in Marine Synechococcus Requires MpeU, an Enzyme with Similarity to Phycoerythrobilin Lyase Isomerases.

Mahmoud Rania M RM Sanfilippo Joseph E JE Nguyen Adam A AA Strnat Johann A JA Partensky Frédéric F Garczarek Laurence L Abo El Kassem Nabil N Kehoe David M DM Schluchter Wendy M WM

Frontiers in microbiology 20170221

Marine Synechococcus has successfully adapted to environments with different light colors, which likely contributes to this genus being the second most abundant group of microorganisms worldwide. Populations of Synechococcus that grow in deep, blue ocean waters contain large amounts of the blue-light absorbing chromophore phycourobilin (PUB) in their light harvesting complexes (phycobilisomes). Here, we show that all Synechococcus strains adapted to blue light possess a gene ...[more]

PMID: 28270800

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Project description:Synechococcus are among the most abundant and widely distributed picocyanobacteria on earth. Cluster 5 phycoerythrobilin-containing (PEB-containing) Synechococcus, the major marine Synechococcus, were considered to prefer high salinity, and they are absent in estuarine ecosystems. However, we have detected PEB-containing Synechococcus in some low-salinity (<15-ppt) areas of the Pearl River estuary at an abundance up to 1.0?×?105 cells ml-1 Two PEB-containing Synechococcus strains (HK01 and LTW-R) were isolated, and tests on them revealed their ability to cope with variations in the salinity (from 14 to 44 ppt). Phylogenetic analysis showed that HK01 belonged to a novel Synechococcus clade (HK1), whereas LTW-R was clustered with S5.2 strains. Whole-genome analysis revealed that a membrane channel protein with glycine zipper motifs is unique to euryhaline Synechococcus The upregulation of this protein, the osmotic sensors, and the heat shock protein HSP20 and the downregulation of the osmolyte biosynthesis enable euryhaline Synechococcus to well adapt to the low and fluctuating salinity in the estuarine environment. In addition, decreasing the salinity in LTW-R strongly downregulated several important metabolic pathways, including photosynthesis, and the Calvin-Benson cycle, whereas its growth was not significantly affected. Moreover, obtaining PEB genes from horizontal gene transfer expands the light niche significantly for euryhaline Synechococcus These results provided new insights into the life strategies and ecological function of marine PEB-containing Synechococcus under the unique environmental condition of estuarine waters, particularly in response to salinity variations.IMPORTANCE Understanding the strategies developed by different microbial groups to adapt to specific niches is critical. Through genome and transcriptome analyses of two newly isolated novel euryhaline Synechococcus strains, this study revealed that cluster 5 phycoerythrobilin-containing Synechococcus, which are thought to be strictly marine strains, could be abundant in low-salinity waters of the Pearl River estuary (salinity <15 ppt) and explained the molecular mechanisms that enabled them to adapt the low and fluctuating salinity in the estuarine environment. This study expands current understanding on mechanisms involved in niche separation of marine Synechococcus lineages.

Dataset Information

Adaptation to Blue Light in Marine Synechococcus Requires MpeU, an Enzyme with Similarity to Phycoerythrobilin Lyase Isomerases.

Publications

Adaptation to Blue Light in Marine <i>Synechococcus</i> Requires MpeU, an Enzyme with Similarity to Phycoerythrobilin Lyase Isomerases.

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