The STN 8 kinase‐ PBCP phosphatase system is responsible for high‐light‐induced reversible phosphorylation of the PSII inner antenna subunit CP 29 in rice

• Published in: The Plant journal : for cell and molecular biology 2017-02, Vol.89 (4), p.681-691
• Main Authors: Betterle, Nico, Poudyal, Roshan Sharma, Rosa, Anthony, Wu, Guangxi, Bassi, Roberto, Lee, Choon‐Hwan
• Format: Article
• Language: English
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13412

Reversible phosphorylation of thylakoid light‐harvesting proteins is a mechanism to compensate for unbalanced excitation of photosystem I ( PSI ) versus photosystem II ( PSII ) under limiting light. In monocots, an additional phosphorylation event on the PSII antenna CP 29 occurs upon exposure to excess light, enhancing resistance to light stress. Different from the case of the major LHCII antenna complex, the STN 7 kinase and its related PPH 1 phosphatase were proven not to be involved in CP 29 phosphorylation, indicating that a different set of enzymes act in the high‐light ( HL ) response. Here, we analyze a rice stn8 mutant in which both PSII core proteins and CP 29 phosphorylation are suppressed in HL , implying that STN 8 is the kinase catalyzing this reaction. In order to identify the phosphatase involved, we produced a recombinant enzyme encoded by the rice ortholog of At PBCP , antagonist of At STN 8, which catalyzes the dephosphorylation of PSII core proteins. The recombinant protein was active in dephosphorylating P‐ CP 29. Based on these data, we propose that the activities of the Os STN 8 kinase and the antagonistic Os PBCP phosphatase, in addition to being involved in the repair of photo‐damaged PSII , are also responsible for the HL ‐dependent reversible phosphorylation of the inner antenna CP 29. Reversible phosphorylation of thylakoid light harvesting proteins contributes to adjust photosynthetic activity upon changes in environmental conditions. Here we show that phosphorylation of CP29, a monomeric light harvesting antenna complex protein, is mediated by the kinase STN8, which is also responsible for turnover of damaged photosystem components, thus connecting dissipative and repair mechanisms.