Abstract
In natural habitats, plants frequently experience rapid changes in the intensity of sunlight. To cope with these changes and maximize growth, plants adjust photosynthetic light utilization in electron transport and photoprotective mechanisms. This involves a proton motive force (PMF) across the thylakoid membrane, postulated to be affected by unknown anion (Cl−) channels. Here we report that a bestrophin-like protein from Arabidopsis thaliana functions as a voltage-dependent Cl− channel in electrophysiological experiments. AtVCCN1 localizes to the thylakoid membrane, and fine-tunes PMF by anion influx into the lumen during illumination, adjusting electron transport and the photoprotective mechanisms. The activity of AtVCCN1 accelerates the activation of photoprotective mechanisms on sudden shifts to high light. Our results reveal that AtVCCN1, a member of a conserved anion channel family, acts as an early component in the rapid adjustment of photosynthesis in variable light environments.
Highlights
In natural habitats, plants frequently experience rapid changes in the intensity of sunlight
We describe a voltage-dependent Cl À channel located in Arabidopsis thylakoids (AtVCCN1), where it functions to fine-tune proton motive force (PMF) and allows the plant to adjust photosynthesis to variable light
Bestrophins function as Ca2 þ -activated monovalent anion channels in mammalian membranes[21]
Summary
Plants frequently experience rapid changes in the intensity of sunlight To cope with these changes and maximize growth, plants adjust photosynthetic light utilization in electron transport and photoprotective mechanisms. This involves a proton motive force (PMF) across the thylakoid membrane, postulated to be affected by unknown anion (Cl À ) channels. AtVCCN1 localizes to the thylakoid membrane, and fine-tunes PMF by anion influx into the lumen during illumination, adjusting electron transport and the photoprotective mechanisms. Light-induced charge separation and coupled H þ uptake into the thylakoid lumen generate a proton motive force (PMF), composed of the transmembrane electric-potential gradient (DC) and H þ concentration gradient (DpH) Both PMF components activate and Hþ drive ATP synthesis by chloroplast F0F1 ATP synthase. DpH and DC can vary with changes in the light environment, and is proposed to be a fine-tuning mechanism for photosynthesis[9]
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