Reduction-Induced Suppression of Electron Flow (RISE) Is Relieved by Non-ATP-Consuming Electron Flow in PCC 7942.

Front Microbiol

Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, Japan.

Published: May 2018

Photosynthetic organisms oxidize P700 to suppress the production of reactive oxygen species (ROS) in photosystem I (PSI) in response to the lower efficiency of photosynthesis under high light and low CO conditions. Previously, we found a positive relationship between reduction of plastoquinone (PQ) pool and oxidation of P700, which we named reduction-induced suppression of electron flow (RISE). In the RISE model, we proposed that the highly reduced state of the PQ pool suppresses Q-cycle turnover to oxidize P700 in PSI. Here, we tested whether RISE was relieved by the oxidation of the PQ pool, but not by the dissipation of the proton gradient (ΔpH) across the thylakoid membrane. Formation of ΔpH can also suppress electron flow to P700, because acidification on the luminal side of the thylakoid membrane lowers oxidation of reduced PQ in the cytochrome / complex. We drove photosynthetic electron transport using HO-scavenging peroxidase reactions. Peroxidase reduces HO with electron donors regenerated along the photosynthetic electron transport system, thereby promoting the formation of ΔpH. Addition of HO to the cyanobacterium PCC 7942 under low CO conditions induced photochemical quenching of chlorophyll fluorescence, enhanced NADPH fluorescence and reduced P700. Thus, peroxidase reactions relieved the RISE mechanism, indicating that P700 oxidation can be induced only by the reduction of PQ to suppress the production of ROS in PSI. Overall, our data suggest that RISE regulates the redox state of P700 in PSI in cooperation with ΔpH regulation.

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5949335PMC
http://dx.doi.org/10.3389/fmicb.2018.00886DOI Listing

Publication Analysis

Top Keywords

electron flow
16
reduction-induced suppression
8
suppression electron
8
flow rise
8
rise relieved
8
pcc 7942
8
oxidize p700
8
suppress production
8
low conditions
8
p700 psi
8

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!