Protein phosphorylation is a key mechanism for the regulation of cellular processes. In plants and algae, many proteins found in thylakoids, particularly components of photosystem II (PSII) and its light-harvesting antenna (LHCII), are reversibly phosphorylated. Phosphorylation of subunits of photosystem I (PSI), the cytochrome b6/f complex and the ATP synthase has also been reported. Differential protein phosphorylation is associated with changes in illumination and various other abiotic parameters, and has been implicated in several regulatory and acclimation responses. Only a few of the molecular processes that modulate the dynamics of acclimation are understood. However, considerable progress has been made in elucidating the mechanisms used during adaptation to changing light conditions. In the short term, plants counteract imbalances in photosynthesis arising from varying light conditions by phosphorylating LHCII. This induces its relocation to PSI and consequently redistributes excitation energy between the photosystems (a so-called state transition). In the long term, unbalanced energy distribution between PSII and PSI is counteracted by changing the rates of accumulation of reaction-centre and light-harvesting proteins, thus adjusting photosystem stoichiometry. Long-term acclimation of photosynthesis appears to involve a signaling network that coordinates alterations in gene expression in nucleus and chloroplast. Recent studies on Arabidopsis mutants indicate that both short- and long-term photosynthetic acclimation involve sensing of the redox state of the plastoquinone pool and activation of the kinase STN7. A second kinase, STN8, is required to phosphorylate PSII core proteins, but stn8 mutants are not significantly impaired in photosynthesis. Here we review recent advances in understanding thylakoid protein phosphorylation and its role in acclimation to changing light conditions. Experimental approaches designed to reveal further details of light acclimation strategies are also discussed.
|Titolo:||Thylakoid protein phosphorylation and its impacts on short- and long-term acclimation of photosynthesis|
PESARESI, PAOLO (Primo)
|Settore Scientifico Disciplinare:||Settore BIO/04 - Fisiologia Vegetale|
|Data di pubblicazione:||29-mag-2009|
|Tipologia:||Book Part (author)|
|Appare nelle tipologie:||03 - Contributo in volume|