H⁺ Transport by K⁺ EXCHANGE ANTIPORTER3 Promotes Photosynthesis and Growth in Chloroplast ATP Synthase Mutants

Abstract

Proton antiport across the thylakoid membrane upregulates photosynthesis and growth in an Arabidopsis mutant with low chloroplast ATP synthase levels and high proton motive force. Footnotes: Author contributions UA designed the study together with MAS and DDS. VC performed most of the experiments with help from DH and analyzed data together with UA. BAM and BS performed MS analysis on thylakoid proteins. MAS and WT quantified thylakoid complexes spectroscopically, measured 77K chlorophyll-a fluorescence emission spectra, cyt-f redox state and performed Chl a fluorescence light response curves. EK carried out the CO2 assimilation measurement. MM, MW, FB and RH performed adenylate quantifications, SB and PJ performed the pigment analysis. UA, VC, MAS and DDS interpreted data with help from SZT.

Dynamic thylakoid stacking and state transitions work synergistically to avoid acceptor-side limitation of photosystem I

“…The increase in P700 + red and Pc + red t½ seen in the WT in HL (Fig. 3D and E) is consistent with photosynthetic control of the cytb6f complex by ΔpH in HL 10,46,47 . The negligible increase in these parameters in HL for tap38 may therefore indicate a reduced ΔpH in this mutant, which would be in line with the lower qE and Y(ND) (Fig.…”

A Holistic Approach to Study Photosynthetic Acclimation Responses of Plants to Fluctuating Light

“…Influx of Cl − ions into the lumen triggers an increase in the pH/ Ψ ratio, by decreasing H + efflux from the thylakoid membranes, inducing a faster NPQ response under sudden increases in light intensities. By contrast, potassium influx to the lumen via the K + antiport (KEA3), has been identified as an important factor in the transition from high to low light (Armbruster et al, 2014(Armbruster et al, , 2016Galvis et al, 2020). KEA3 transfers K + into the lumen and H + out to the chloroplast stroma, decreasing pH but maintaining the Ψ necessary for ATP production.…”

Shade lichens are characterized by rapid relaxation of non-photochemical quenching on transition to darkness

“…First, shade species may possess higher activities of xanthophyll epoxidases (Kaiser et al 2019). Second, the speed of NPQ relaxation is strongly modulated by the K + antiporter KEA3 (Armbruster et al 2014(Armbruster et al , 2016Correa Galvis et al 2020). KEA3 transfers K + into the lumen and H + out to the chloroplast stroma, decreasing pH and accelerating NPQ relaxation, leading to a fast recovery of CO 2 assimilation (Armbruster et al 2014).…”