Molecular bases of an alternative dual-enzyme system for light color acclimation of marine $Synechococcus$ cyanobacteria - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Proceedings of the National Academy of Sciences of the United States of America Année : 2021

Molecular bases of an alternative dual-enzyme system for light color acclimation of marine $Synechococcus$ cyanobacteria

Théophile Grébert
  • Fonction : Auteur
Adam A Nguyen
  • Fonction : Auteur
Suman Pokhrel
  • Fonction : Auteur
Kes Lynn
  • Fonction : Auteur
Morgane Ratin
Bo Chen
  • Fonction : Auteur
Allissa M Haney
  • Fonction : Auteur
Jonathan A Karty
  • Fonction : Auteur
Jonathan C Trinidad
  • Fonction : Auteur
Wendy M Schluchter
  • Fonction : Auteur
David M Kehoe
  • Fonction : Auteur

Résumé

Marine Synechococcus cyanobacteria owe their ubiquity in part to the wide pigment diversity of their lightharvesting 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-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 upregulated 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. Significance Of all cyanobacteria on Earth, marine Synechococcus are those displaying the greatest pigment diversity. The most sophisticated pigment type are cells able to reversibly modify their color by a phenomenon called Type
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hal-03153666 , version 1 (26-02-2021)

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Théophile Grébert, Adam A Nguyen, Suman Pokhrel, Kes Lynn, Morgane Ratin, et al.. Molecular bases of an alternative dual-enzyme system for light color acclimation of marine $Synechococcus$ cyanobacteria. Proceedings of the National Academy of Sciences of the United States of America, 2021, ⟨10.1073/pnas.2019715118⟩. ⟨hal-03153666⟩
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