Neoxanthin affects the stability of the C 2 S 2 M 2 ‐type photosystem II supercomplexes and the kinetics of state transition in Arabidopsis

Neoxanthin (Neo), only bound to the peripheral antenna proteins of photosystem II (PSII), is a conservative carotenoid in all green plants. It has been demonstrated that Neo plays an important role in photoprotection and its deficiency fails to impact LHCII stability in vitro and indoor plant growth in vivo. Whether Neo is involved in maintaining the PSII complex structure or adaptive mechanisms for everchanging environment has not yet been concerned. In this study, the role of Neo in maintaining the structure and function of the PSII-LHCII supercomplexes was studied using the Neo deficient Arabidopsis mutants. Our results showed that Neo deficiency had little effect on the electron transport capacity and the plant fitness, but the PSII-LHCII supercomplexes were significantly impacted due to lack of Neo. In the absence of Neo, the M-type LHCII trimer cannot effectively associate to the C2 S2 -type PSII-LHCII supercomplexes even in the moderate light conditions. Interestingly, Neo deficiency also leads to decreased PSII protein phosphorylation but rapid transition from state 1 to state 2. We suggest that Neo might enforce the interactions between LHCII and the minor antennas and the absence of Neo makes M-type LHCII disassociate from the PSII complex and leads to the disassembly of the PSII-LHCII C2 S2 M2 supercomplexes, which results in alterations in the phosphorylation patterns of the thylakoid photosynthetic proteins and the kinetics of state transition.