679 / 2019-04-30 22:12:23

Photosynthesis and growth in ATP synthase limited mutants depend on thylakoid proton transport by KEA3

Photosynthesis,Membrane transport,Bioenergetics

全体主题 > Photosynthesis

The composition of pmf is regulated by thylakoid ion transport. Channels dissipate the membrane potential (Δψ) to allow for a higher fraction of pmf stored as ΔpH. This is important for adequately switching on the heat dissipation mechanism and thus photoprotection in high light. K+/H+ antiport across the thylakoid membrane via KEA3 instead reduces the fraction of pmf stored as ΔpH and thereby lowers heat dissipation. Thus, KEA3 activity allows for increased light use efficiency, particularly during light transients. Because KEA3 activity does not strongly affect photosynthesis in the steady-state, the effects of thylakoid K+/H+ antiport have been difficult to quantify. Here, we show that in the high pmf mutant cgl160, with decreased levels of the chloroplast ATP synthase, KEA3 plays an important role for efficient photosynthesis and plant growth under steady-state conditions. By comparing cgl160 single with cgl160kea3 double mutants, we show that in the cgl160 background, KEA3 activity decreases lumenal pH, thereby increasing light use efficiency and electron transport capacity. While cgl160 mutants grow only slightly smaller than WT, the additional loss of KEA3 in this mutant causes a severe growth retardation with cgl160kea3 only accumulating half of the biomass of cgl160. Taken together, our data provide first evidence that a KEA3-dependent high fraction of pmf stored as Δψ benefits plant photosynthesis and growth under specific steady-state conditions.