Biology subjects

Chazaux, M.

Publications and source records attributed to Chazaux, M..

3 recordsLinked to original sources

bioRxiv2025

Acclimation of photosynthesis began with a Cu-binding superoxide detoxifying enzyme

Plant acclimation is a growing scientific concept, at molecular, cellular and global scales. All photosynthetic organisms that created an oxic atmosphere on earth possess a gene of unknown function "Acclimation of Photosynthesis to the Environment 1". Here we show that APE1 encodes a thylakoid-bound protein with a unique motif that binds copper and detoxifies the superoxide anion radical, O2*-. Maturation of the recombinant APE1 protein from Chlamydomonas reinhardtii requires formation of cysteine disulfide bonds after copper binding or via a high affinity interaction with a copper chaperone (Plastid Copper Chaperone 1) that boosts its scavenging capacity for O2*-. APE1 co-occurs in evolution with Photosystem II oxygen evolving proteins and it is the archaic O2*- detoxifying enzyme for acclimating photosynthesis to an oxygenic environment.

plant biology↗

bioRxiv2020

Regulation of light harvesting in Chlamydomonas: two protein phosphatases are involved in state transitions

Protein phosphorylation plays important roles in short-term regulation of photosynthetic electron transfer. In a mechanism known as state transitions, the kinase STATE TRANSITION 7 (STT7) of Chlamydomonas reinhardtii phosphorylates components of light-harvesting antenna complex II (LHCII). This reversible phosphorylation governs the dynamic allocation of a part of LHCII to photosystem I or photosystem II, depending on light conditions and metabolic demands. Little is however known in the green alga on the counteracting phosphatase(s). In Arabidopsis, the homologous kinase STN7 is specifically antagonized by PROTEIN PHOSPHATASE 1/THYLAKOID-ASSOCIATED PHOSPHATASE 38 (PPH1/TAP38). Furthermore, the paralogous kinase STN8 and the countering phosphatase PHOTOSYSTEM II PHOSPHATASE (PBCP), which count subunits of PSII amongst their major targets, influence thylakoid architecture and high-light tolerance. Here we analyze state transitions in C. reinhardtii mutants of the two homologous phosphatases, CrPPH1 and CrPBCP. The transition from state 2 to state 1 is retarded in pph1, and surprisingly also in pbcp. However both mutants can eventually return to state 1. In contrast, the double mutant pph1;pbcp appears strongly locked in state 2. The complex phosphorylation patterns of the LHCII trimers and of the monomeric subunits are affected in the phosphatase mutants. Their analysis indicates that the two phosphatases have different yet overlapping sets of protein targets. The dual control of thylakoid protein de-phosphorylation and the more complex antenna phosphorylation patterns in Chlamydomonas compared to Arabidopsis are discussed in the context of the stronger amplitude of state transitions and the more diverse LHCII isoforms in the alga.

plant biology↗

bioRxiv2020

ACCLIMATION OF PHOTOSYNTHESIS TO THE ENVIRONMENT 1 regulates Photosystem II Supercomplex dynamics in response to light in Chlamydomonas reinhardtii

Photosynthetic organisms require acclimation mechanisms to regulate photosynthesis in response to light conditions. Here, two mutant alleles of ACCLIMATION OF PHOTOSYNTHESIS TO THE ENVIRONMENT 1 (ape1) have been characterized in Chlamydomonas reinhardtii. The ape1 mutants are photosensitive and show PSII photoinhibition during high light acclimation or under high light stress. The ape1 mutants retain more PSII super-complexes and have changes to thylakoid stacking relative to control strains during photosynthetic growth at different light intensities. The APE1 protein is found in all oxygenic phototrophs and encodes a 25 kDa thylakoid protein that interacts with the Photosystem II core complex as monomers, dimers and supercomplexes. We propose a model where APE1 bound to PSII supercomplexes releases core complexes and promotes PSII heterogeneity influencing the stacking of Chlamydomonas thylakoids. APE1 is a regulator in light acclimation and its function is to reduce over-excitation of PSII centres and avoid PSII photoinhibition to increase the resilience of photosynthesis to high light.

plant biology↗