DOI:
Authors:
Shin‐Ichiro Ozawa, Félix Buchert, Ruby Reuys, Michael Hippler, Yuichiro Takahashi
Abstract:
Abstract Linear photosynthetic electron flow (LEF) produces NADPH and generates a proton electrochemical potential gradient across the thylakoid membrane used to synthesize ATP, both of which are required for CO 2 fixation. As cellular demand for ATP and NADPH are variable, cyclic electron flow (CEF) between PSI and cytochrome b 6 f complex ( b 6 f ) produces extra ATP. The b 6 f regulates LEF and CEF via photosynthetic control, which is a pH-dependent b 6 f slowdown of plastoquinol oxidation at the lumenal site. This protection mechanism is triggered at more alkaline lumen pH in the pgr1 mutant of the vascular plant Arabidopsis thaliana , carrying Pro194Leu in the b 6 f Rieske Iron-sulfur protein. In this work, we introduced pgr1 mutation in the green alga Chlamydomonas reinhardtii ( PETC-P171L ). Consistent with pgr1 phenotype, PETC-P171L displayed an impaired NPQ induction along with slower photoautotrophic growth under high light conditions. Our data provides evidence that the ΔpH component in PETC-P171L is dependent on oxygen availability. Only under low oxygen conditions the ΔpH component was sufficient to trigger a phenotype in algal PETC-P171L where the mutant b 6 f was more restricted to oxidize the PQ pool and showed a diminished electron flow through the b 6 f complex. One sentence summary Change of PETC to P171L via site directed mutagenesis alters the pH dependency of the photosynthetic control mechanism