Protein kinases and phosphatases involved in the acclimation of the photosynthetic apparatus to a changing light environment

Abstract

Photosynthetic organisms are subjected to frequent changes in light quality and quantity and need to respond accordingly. These acclimatory processes are mediated to a large extent through thylakoid protein phosphorylation. Recently, two major thylakoid protein kinases have been identified and characterized. The Stt7/STN7 kinase is mainly involved in the phosphorylation of the LHCII antenna proteins and is required for state transitions. It is firmly associated with the cytochrome b 6 f complex, and its activity is regulated by the redox state of the plastoquinone pool. The other kinase, Stl1/STN8, is responsible for the phosphorylation of the PSII core proteins. Using a reverse genetics approach, we have recently identified the chloroplast PPH1/TAP38 and PBPC protein phosphatases, which counteract the activity of STN7 and STN8 kinases, respectively. They belong to the PP2C-type phosphatase family and are conserved in land plants and algae. The picture that emerges from these studies is that of a complex regulatory network of chloroplast protein kinases and phosphatases that is involved in light acclimation, in maintenance of the plastoquinone redox poise under fluctuating light and in the adjustment to metabolic needs.

Structural changes of the thylakoid membrane network induced by high light stress in plant chloroplasts

“…The altered conformation of phosphorylated proteins leads to changed recognition motifs between proteins, inducing their separation. In accordance with both models is that partial destacking by PSII core phosphorylation is mechanistically very similar to partial destacking triggered by LHCII phosphorylation under state transition that is catalysed mainly by the STN7 kinase [37,38,65]. Interestingly, the degree of partial destacking under state transition in low light [66] is similar to the degree of destacking under high light stress [49] indicating a similar mechanism.…”

“…The multi-step PSII repair cycle is outlined in figure 1. The mainstream model is that after high-light-induced damage, the PSII subunits D1, D2, CP43 and psbH are phosphorylated (figure 1(2)), catalysed mainly by the STN8 kinase [34,35] and possibly by the STN7 kinase [36][37][38]. As evidence exists that in STN7/STN8 double mutants, the disassembly of the PSII holocomplex is inhibited [33,[39][40][41], it was hypothesized that phosphorylation of core subunits triggers disassembly ( figure 1(3)).…”

Connection of the Photochemical Reflectance Index (PRI) with the Photosystem II Quantum Yield and Nonphotochemical Quenching Can Be Dependent on Variations of Photosynthetic Parameters among Investigated Plants: A Meta-Analysis

“…The contribution of these processes to the total NPQ depends on environmental conditions [115,116] and the time of their development [117]. The quantum yield of photosystem II is connected with all components of NPQ [113,118,119] as well as with the ratio of the linear and cyclic electron flows [117,120], production of reactive oxygen species [121], etc. Also, there are additional factors which can complicate interaction between photosynthetic parameters and PRI under the action of stressors.…”

PsbN Is Required for Assembly of the Photosystem II Reaction Center in Nicotiana tabacum

“…The RC proteins D1, D2, and CP43 are mainly phosphorylated by STN8 kinase, whereas the outer antenna proteins LHCII and CP29 are substrates for the STN7 kinase (Rochaix et al, 2012). We chose three conditions, dark, red light, and far-red light, to follow the PSII phosphorylation pattern in the wild type and mutants ( Figure 10A).…”