Exogenously-supplied trehalose protects photosystem II by promoting
cyclic electron flow in winter wheat under heat and drought stress
Abstract
Trehalose protects and stabilizes the reaction center and improves
photosystem II (PS II) activity. However, the underlying mechanism
remains unknown. Cyclic electron flow is an important mechanism to
protect PS II under stress. This study focused on the effects of
exogenous trehalose on the activity of PS II, D1 protein content, the
plastoquinone (PQ) pool, and ATP synthase activity in wheat seedlings
under heat and drought stress to explore the relationship between
trehalose and cyclic electron flow (CEF). Our experimental results
indicated that heat and drought stress decreased the maximal
photochemical efficiency of PS II (Fv/Fm) and the electron transport
rate of PS II (EFR(II)), whereas the trehalose pretreatment improved
photochemical efficiency and the electron transport rate of PS II. The
trehalose pretreatment stimulated CEF under heat and drought stress.
Furthermore, the proton gradient (ΔpH) across the thylakoid membrane and
ATPase activity increased. The higher ΔpH and ATPase activity played a
key role in protecting PS II under stress. Inhibition of the oxidized PQ
pool caused by heat and drought stress was alleviated by the trehalose
pretreatment. Thus, our results show that photoinhibition of heat and
drought-stressed plants was alleviated by the trehalose pretreatment.
Our findings further reveal that this effect was mediated by CEF and the
PQ pool.