GreenCut protein CPLD49 of Chlamydomonas reinhardtii associates with thylakoid membranes and is required for cytochrome b₆f complex accumulation

Abstract

The GreenCut encompasses a suite of nucleus-encoded proteins with orthologs among green lineage organisms (plants, green algae), but that are absent or poorly conserved in non-photosynthetic/heterotrophic organisms. In Chlamydomonas reinhardtii, CPLD49 (Conserved in Plant Lineage and Diatoms49) is an uncharacterized GreenCut protein that is critical for maintaining normal photosynthetic function. We demonstrate that a cpld49 mutant has impaired photoautotrophic growth under high-light conditions. The mutant exhibits a nearly 90% reduction in the level of the cytochrome b f complex (Cytb f), which impacts linear and cyclic electron transport, but does not compromise the ability of the strain to perform state transitions. Furthermore, CPLD49 strongly associates with thylakoid membranes where it may be part of a membrane protein complex with another GreenCut protein, CPLD38; a mutant null for CPLD38 also impacts Cytb f complex accumulation. We investigated several potential functions of CPLD49, with some suggested by protein homology. Our findings are congruent with the hypothesis that CPLD38 and CPLD49 are part of a novel thylakoid membrane complex that primarily modulates accumulation, but also impacts the activity of the Cytb f complex. Based on motifs of CPLD49 and the activities of other CPLD49-like proteins, we suggest a role for this putative dehydrogenase in the synthesis of a lipophilic thylakoid membrane molecule or cofactor that influences the assembly and activity of Cytb f.

Physiological and proteomic analyses revealed the response mechanisms of two different drought-resistant maize varieties

“…This electron transport pathway is known as linear electron flow (LEF). Moreover, the cycling electron flow (CEF) around PSI passes through the Cytb6f complex, generates ΔpH, and drives ATP synthesis without concomitant NADPH generation [ 25 ].…”

ZnJ6 Is a Thylakoid Membrane DnaJ-Like Chaperone with Oxidizing Activity in Chlamydomonas reinhardtii

“…Membrane and soluble fractions were separated by centrifugation at 100,000× g for 1 h at 4 • C. The soluble proteins were precipitated using 20% TCA (final concentration) for 1 h at 4 • C and washed twice with 100% acetone. Pellets of both soluble and membrane proteins were dissolved in 40 mM Tris-HCl pH 7.4, 5 mM EDTA, 4% SDS [44].…”

“…The thylakoid membranes were spun down at 68,600× g for 20 min at 4 • C and washed twice with buffer containing 5 mM HEPES-KOH, pH 7.5, 10 mM EDTA, and a cocktail of PIs. The thylakoid pellet was resuspended in 200 µL of the same buffer [44].…”

Physiological and Proteomic Analysis Revealed the Response Mechanisms of two Different Grought-resistant Maize Varieties

“…This electron transport pathway is termed linear electron ow (LEF). In addition, the cycling electron ow (CEF) around PSI, which also passes through the Cytb 6 f complex, can generate ΔpH and drives ATP synthesis but without concomitant generation of NADPH [25].…”