Abstract
Phosphorylation of the light-harvesting complex II (LHCII) is a central trigger for the reorganization of the photosynthetic complexes in the thylakoid membrane during short-term light acclimation. The major kinase involved in LHCII phosphorylation is STATE TRANSITION 7 (STN7), and its activity is mostly counteracted by a thylakoid-associated phosphatase, PROTEIN PHOSPHATASE 1/THYLAKOID ASSOCIATED PHOSPHATASE 38 (PPH1/TAP38). This kinase/phosphatase pair responds to the redox status of the photosynthetic electron transport chain. In Arabidopsis thaliana, Lhcb1 and Lhcb2 subunits of the LHCII trimers are the major targets of phosphorylation and have different roles in the acclimation of the photosynthetic machinery. Another antagonistic kinase and phosphatase pair, STATE TRANSITION 8 (STN8) and PHOTOSYSTEM II PHOSPHATASE (PBCP) target a different set of thylakoid proteins. Here, we analyzed double, triple, and quadruple knockout mutants of these kinases and phosphatases. In multiple mutants, lacking STN7, in combination with one or both phosphatases, but not STN8, the phosphorylation of LHCII was partially restored. The recovered phosphorylation favors Lhcb1 over Lhcb2 and results in a better adaptation of the photosynthetic apparatus and increased plant growth under fluctuating light. This set of mutants allowed to unveil a contribution of STN8-dependent phosphorylation in the acclimation to rapid light variations.
Highlights
The conversion of photon energy into chemical energy drives the supply of organic compounds to the biosphere
When the second major kinase acting on thylakoid proteins (STN8) is knocked-out in the quadruple mutant, the phosphorylation is completely lost (Figure 1), suggesting that this kinase is essentially responsible for the light-harvesting complex II (LHCII) phosphorylation in the absence of STATE TRANSITION 7 (STN7)
STN7 and STATE TRANSITION 8 (STN8), do not have exactly the same localization in the thylakoid membrane (Wunder et al, 2013), we tested if the recovered LHCII phosphorylation repartition was affected
Summary
The conversion of photon energy into chemical energy drives the supply of organic compounds to the biosphere It occurs in the thylakoid membrane through the action of a set of protein/ pigment complexes capable of oxidizing water to oxygen, producing reducing agents that are used in plant metabolism. The rapid energy transfer ensures the sustained excitation of PSII that is necessary to perform the two photochemical turnovers required for the reduction of QB (PQ, plastoquinone) to QB2−, which is further protonated to plastoquinol (PQH2) The latter acts in thylakoid membrane as the electron carrier to cytb f, contributing to the formation of the proton gradient across the thylakoid membrane (Barber, 2016). The antenna system acts dissipating the energy excess by a process known as nonphotochemical quenching (NPQ); this protects the two photosystems reaction centers and requires both the monomeric and the trimeric LHCII (Dall’Osto et al, 2017)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
