RT Journal Article
SR Electronic
T1 Flavodiiron Proteins Promote Fast and Transient O<sub>2</sub> Photoreduction in <em>Chlamydomonas</em>
JF Plant Physiology
JO Plant Physiol.
FD American Society of Plant Biologists
SP 1825
OP 1836
DO 10.1104/pp.17.00421
VO 174
IS 3
A1 Chaux, Frédéric
A1 Burlacot, Adrien
A1 Mekhalfi, Malika
A1 Auroy, Pascaline
A1 Blangy, Stéphanie
A1 Richaud, Pierre
A1 Peltier, Gilles
YR 2017
UL http://www.plantphysiol.org/content/174/3/1825.abstract
AB During oxygenic photosynthesis, the reducing power generated by light energy conversion is mainly used to reduce carbon dioxide. In bacteria and archae, flavodiiron (Flv) proteins catalyze O2 or NO reduction, thus protecting cells against oxidative or nitrosative stress. These proteins are found in cyanobacteria, mosses, and microalgae, but have been lost in angiosperms. Here, we used chlorophyll fluorescence and oxygen exchange measurement using [18O]-labeled O2 and a membrane inlet mass spectrometer to characterize Chlamydomonas reinhardtii flvB insertion mutants devoid of both FlvB and FlvA proteins. We show that Flv proteins are involved in a photo-dependent electron flow to oxygen, which drives most of the photosynthetic electron flow during the induction of photosynthesis. As a consequence, the chlorophyll fluorescence patterns are strongly affected in flvB mutants during a light transient, showing a lower PSII operating yield and a slower nonphotochemical quenching induction. Photoautotrophic growth of flvB mutants was indistinguishable from the wild type under constant light, but severely impaired under fluctuating light due to PSI photo damage. Remarkably, net photosynthesis of flv mutants was higher than in the wild type during the initial hour of a fluctuating light regime, but this advantage vanished under long-term exposure, and turned into PSI photo damage, thus explaining the marked growth retardation observed in these conditions. We conclude that the C. reinhardtii Flv participates in a Mehler-like reduction of O2, which drives a large part of the photosynthetic electron flow during a light transient and is thus critical for growth under fluctuating light regimes.GlossaryCEFcyclic electron flowCLiPChlamydomonas Library ProjectECSelectrochromic carotenoid shiftMIMSmembrane inlet mass spectrometerMVmethyl viologenNPQnonphotochemical quenching