Acyl‐turnover of acylplastoquinol enhances recovery of photodamaged PSII in Synechocystis

• Published in: The Plant journal : for cell and molecular biology 2024-11, Vol.120 (4), p.1317-1325
• Main Authors: Jimbo, Haruhiko, Torii, Mana, Fujino, Yuichiro, Tanase, Yoshiki, Kurima, Kazuki, Sato, Naoki, Wada, Hajime
• Format: Article
• Language: English
• Subjects: acylplastoquinol; Aeration; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Chemical synthesis; Deacylation; Disruption; Electron Transport; Light; Lipase; Lipase - genetics; Lipase - metabolism; online‐reducing HPLC; Photoinhibition; photoinhibition of PSII; Photons; Photosynthesis; Photosystem II; Photosystem II Protein Complex - metabolism; Plastoquinol; plastoquinone; Plastoquinone - analogs & derivatives; Plastoquinone - metabolism; PSII repair; Recovery; Synechocystis; Synechocystis - genetics; Synechocystis - metabolism; Synechocystis sp. PCC 6803
• ISSN: 0960-7412; 1365-313X; 1365-313X
• DOI: 10.1111/tpj.17051

SUMMARY Photosynthetic electron transport is carried out by the electron carrier, plastoquinone (PQ). Recently, another form of PQ, acylplastoquinol (APQ), was discovered in Synechocystis sp. PCC 6803 (Synechocystis), but its physiological function in photosynthesis is unclear. In the present study, we identified a lipase encoded in sll0482 gene in Synechocystis that deacylates APQ and releases a free fatty acid and a reduced PQ (plastoquinol, PQH2), which we named acylplastoquinol lipase (APL). Disruption of apl gene increased APQ content, and recovery of photodamaged PSII under low light (LL) after the exposure to very high light (vHL) at 2500 μmol photons m−2 sec−1 without aeration (vHL) for 60 min, was suppressed in the Δapl cells. Δapl cells also show the slow rate of de novo synthesis of D1, a reaction center of PSII under such condition. Under high light, the cellular growth of Δapl was inhibited; however, disruption of apl gene did not affect the photosynthetic activity or photoinhibition of PSII. In wild‐type cells, APQ content increased under vHL condition. Also, APQ was converted to PQH2 after transfer to LL with aeration by ambient air. Such striking changes in APQ were not observed in Δapl cells. The deacylation of APQ by APL may help repair PSII when PSII cannot drive photosynthetic electron transport efficiently. Significance Statement The physiological role of recently discovered acylplastoquinol (APQ) in photosynthesis is unclear. APQ content was increased under severe photo‐oxidative stress. It was deacylated by APQ lipase to produce a plastoquinol (PQH2) and a free fatty acid. Produced PQH2 may be required for the efficient repair of PSII when PSII cannot drive photosynthetic electron transport efficiently.