TEF8 regulates H 2 photoproduction by destabilizing PSII supercomplexes in Chlamydomonas

SUMMARY Hydrogen (H 2 ) photoproduction by green microalgae offers a promising renewable energy strategy, yet its efficiency is constrained by the oxygen sensitivity of hydrogenases and the availability of photosynthetic electrons produced by photosystem II (PSII). Conventional approaches such as sulfur deprivation to induce H 2 photoproduction inevitably lead to downregulation of PSII and thereafter restriction of the sufficient electron supply to hydrogenases. Here, we show that the thylakoid membrane phosphatase TEF8 (Thylakoid Enriched Fraction 8) acts as a negative regulator of H 2 photoproduction in Chlamydomonas reinhardtii under sulfur‐deprivation conditions. Compared with wild type, the tef8 knockout mutant exhibits significantly enhanced H 2 evolution and increased stability of PSII supercomplexes when H 2 photoproduction was induced. Further biochemical analyses reveal that TEF8 is involved in the dephosphorylation of PSII subunits, promoting the degradation of PSII core complex under sulfur deprivation. Loss of TEF8 function impairs dephosphorylation of D2 and CP29, thereby stabilizing PSII supercomplexes and maintaining higher electron flux to hydrogenases under sulfur‐deprivation conditions. These findings identify TEF8 as a regulatory protein that fine‐tunes PSII activity and photosynthetic electron flow, thereby modulating hydrogen photoproduction efficiency.