@article {dufour_differential_2024,
	title = {Differential acclimation kinetics of the two forms of type IV chromatic acclimaters occurring in marine Synechococcus cyanobacteria},
	journal = {Frontiers in Microbiology},
	volume = {15},
	year = {2024},
	pages = {1349322},
	abstract = {Synechococcus , the second most abundant marine phytoplanktonic organism, displays the widest variety of pigment content of all marine oxyphototrophs, explaining its ability to colonize all spectral niches occurring in the upper lit layer of oceans. Seven Synechococcus pigment types (PTs) have been described so far based on the phycobiliprotein composition and chromophorylation of their light-harvesting complexes, called phycobilisomes. The most elaborate and abundant PT (3d) in the open ocean consists of cells capable of type IV chromatic acclimation (CA4), i.e., to reversibly modify the ratio of the blue light-absorbing phycourobilin (PUB) to the green light-absorbing phycoerythrobilin (PEB) in phycobilisome rods to match the ambient light color. Two genetically distinct types of chromatic acclimaters, so-called PTs 3dA and 3dB, occur at similar global abundance in the ocean, but the precise physiological differences between these two types and the reasons for their complementary niche partitioning in the field remain obscure. Here, photoacclimation experiments in different mixes of blue and green light of representatives of these two PTs demonstrated that they differ by the ratio of blue-to-green light required to trigger the CA4 process. Furthermore, shift experiments between 100\% blue and 100\% green light, and vice-versa , revealed significant discrepancies between the acclimation pace of the two types of chromatic acclimaters. This study provides novel insights into the finely tuned adaptation mechanisms used by Synechococcus cells to colonize the whole underwater light field.},
	keywords = {RCC2319, RCC2369, RCC2374, RCC2533, RCC2553, RCC2571, RCC515, rcc555, RCC751},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2024.1349322},
	url = {https://www.frontiersin.org/articles/10.3389/fmicb.2024.1349322/full},
	author = {Dufour, Louison and Garczarek, Laurence and Gouriou, Bastian and Clairet, Julia and Ratin, Morgane and Partensky, Fr{\'e}d{\'e}ric}
}
@article {ferrieux_comparative_2022,
	title = {Comparative Thermophysiology of Marine Synechococcus CRD1 Strains Isolated From Different Thermal Niches in Iron-Depleted Areas},
	journal = {Frontiers in Microbiology},
	volume = {13},
	year = {2022},
	abstract = {Marine Synechococcus cyanobacteria are ubiquitous in the ocean, a feature likely related to their extensive genetic diversity. Amongst the major lineages, clades I and IV preferentially thrive in temperate and cold, nutrient-rich waters, whilst clades II and III prefer warm, nitrogen or phosphorus-depleted waters. The existence of such cold (I/IV) and warm (II/III) thermotypes is corroborated by physiological characterization of representative strains. A fifth clade, CRD1, was recently shown to dominate the Synechococcus community in iron-depleted areas of the world ocean and to encompass three distinct ecologically significant taxonomic units (ESTUs CRD1A-C) occupying different thermal niches, suggesting that distinct thermotypes could also occur within this clade. Here, using comparative thermophysiology of strains representative of these three CRD1 ESTUs we show that the CRD1A strain MITS9220 is a warm thermotype, the CRD1B strain BIOS-U3-1 a cold temperate thermotype, and the CRD1C strain BIOS-E4-1 a warm temperate stenotherm. Curiously, the CRD1B thermotype lacks traits and/or genomic features typical of cold thermotypes. In contrast, we found specific physiological traits of the CRD1 strains compared to their clade I, II, III, and IV counterparts, including a lower growth rate and photosystem II maximal quantum yield at most temperatures and a higher turnover rate of the D1 protein. Together, our data suggests that the CRD1 clade prioritizes adaptation to low-iron conditions over temperature adaptation, even though the occurrence of several CRD1 thermotypes likely explains why the CRD1 clade as a whole occupies most iron-limited waters.},
	keywords = {RCC2374, RCC2385, RCC2533, RCC2534, RCC2571, RCC515, rcc539, rcc791},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2022.893413},
	url = {https://www.frontiersin.org/article/10.3389/fmicb.2022.893413},
	author = {Ferrieux, Mathilde and Dufour, Louison and Dor{\'e}, Hugo and Ratin, Morgane and Gu{\'e}neugu{\`e}s, Audrey and Chasselin, L{\'e}o and Marie, Dominique and Rigaut-jalabert, Fabienne and Le Gall, Florence and Sciandra, Th{\'e}o and Monier, Garance and Hoebeke, Mark and Corre, Erwan and Xia, Xiaomin and Liu, Hongbin and Scanlan, David J. and Partensky, Fr{\'e}d{\'e}ric and Garczarek, Laurence}
}
@article {carrigee_phycoerythrobilin_2022,
	title = {The phycoerythrobilin isomerization activity of MpeV in Synechococcus sp. WH8020 is prevented by the presence of a histidine at position 141 within its phycoerythrin-I β-subunit substrate},
	journal = {Frontiers in Microbiology},
	volume = {13},
	year = {2022},
	pages = {1011189},
	abstract = {Marine Synechococcus efficiently harvest available light for photosynthesis using complex antenna systems, called phycobilisomes, composed of an allophycocyanin core surrounded by rods, which in the open ocean are always constituted of phycocyanin and two phycoerythrin (PE) types: PEI and PEII. These cyanobacteria display a wide pigment diversity primarily resulting from differences in the ratio of the two chromophores bound to PEs, the green-light absorbing phycoerythrobilin and the blue-light absorbing phycourobilin. Prior to phycobiliprotein assembly, bilin lyases post-translationally catalyze the ligation of phycoerythrobilin to conserved cysteine residues on α- or β-subunits, whereas the closely related lyase-isomerases isomerize phycoerythrobilin to phycourobilin during the attachment reaction. MpeV was recently shown in Synechococcus sp. RS9916 to be a lyase-isomerase which doubly links phycourobilin to two cysteine residues (C50 and C61; hereafter C50, 61) on the β-subunit of both PEI and PEII. Here we show that Synechococcus sp. WH8020, which belongs to the same pigment type as RS9916, contains MpeV that demonstrates lyase-isomerase activity on the PEII β-subunit but only lyase activity on the PEI β-subunit. We also demonstrate that occurrence of a histidine at position 141 of the PEI β-subunit from WH8020, instead of a leucine in its counterpart from RS9916, prevents the isomerization activity by WH8020 MpeV, showing for the first time that both the substrate and the enzyme play a role in the isomerization reaction. We propose a structural-based mechanism for the role of H141 in blocking isomerization. More generally, the knowledge of the amino acid present at position 141 of the β-subunits may be used to predict which phycobilin is bound at C50, 61 of both PEI and PEII from marine Synechococcus strains.},
	keywords = {RCC2437, RCC307, RCC751},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2022.1011189},
	url = {https://www.frontiersin.org/articles/10.3389/fmicb.2022.1011189/full},
	author = {Carrigee, Lyndsay A. and Frick, Jacob P. and Liu, Xindi and Karty, Jonathan A. and Trinidad, Jonathan C. and Tom, Irin P. and Yang, Xiaojing and Dufour, Louison and Partensky, Fr{\'e}d{\'e}ric and Schluchter, Wendy M.}
}
@article {grebert_molecular_2021,
	title = {Molecular bases of an alternative dual-enzyme system for light color acclimation of marine \textit{Synechococcus cyanobacteria},
	journal = {Proceedings of the National Academy of Sciences},
	volume = {118},
	number = {9},
	year = {2021},
	pages = {e2019715118},
	abstract = {<p>Marine Synechococcus cyanobacteria owe their ubiquity in part to the wide pigment diversity of their light-harvesting complexes. In open ocean waters, cells predominantly possess sophisticated antennae with rods composed of phycocyanin and two types of phycoerythrins (PEI and PEII). Some strains are specialized for harvesting either green or blue light, while others can dynamically modify their light absorption spectrum to match the dominant ambient color. This process, called type IV chromatic acclimation (CA4), has been linked to the presence of a small genomic island occurring in two configurations (CA4-A and CA4-B). While the CA4-A process has been partially characterized, the CA4-B process has remained an enigma. Here we characterize the function of two members of the phycobilin lyase E/F clan, MpeW and MpeQ, in Synechococcus sp. strain A15-62 and demonstrate their critical role in CA4-B. While MpeW, encoded in the CA4-B island and up-regulated in green light, attaches the green light-absorbing chromophore phycoerythrobilin to cysteine-83 of the PEII α-subunit in green light, MpeQ binds phycoerythrobilin and isomerizes it into the blue light-absorbing phycourobilin at the same site in blue light, reversing the relationship of MpeZ and MpeY in the CA4-A strain RS9916. Our data thus reveal key molecular differences between the two types of chromatic acclimaters, both highly abundant but occupying distinct complementary ecological niches in the ocean. They also support an evolutionary scenario whereby CA4-B island acquisition allowed former blue light specialists to become chromatic acclimaters, while former green light specialists would have acquired this capacity by gaining a CA4-A island.</p>
},
	keywords = {RCC2374, to add},
	issn = {0027-8424, 1091-6490},
	doi = {10.1073/pnas.2019715118},
	url = {http://www.pnas.org/lookup/doi/10.1073/pnas.2019715118},
	author = {Gr{\'e}bert, Th{\'e}ophile and Nguyen, Adam A. and Pokhrel, Suman and Joseph, Kes Lynn and Ratin, Morgane and Dufour, Louison and Chen, Bo and Haney, Allissa M. and Karty, Jonathan A. and Trinidad, Jonathan C. and Garczarek, Laurence and Schluchter, Wendy M. and Kehoe, David M. and Partensky, Fr{\'e}d{\'e}ric}
}
