Role of an ancient light-harvesting protein of PSI in light absorption and photoprotection

Abstract

Diverse algae of the red lineage possess chlorophyll a-binding proteins termed LHCR, comprising the PSI light-harvesting system, which represent an ancient antenna form that evolved in red algae and was acquired through secondary endosymbiosis. However, the function and regulation of LHCR complexes remain obscure. Here we describe isolation of a Nannochloropsis oceanica LHCR mutant, named hlr1, which exhibits a greater tolerance to high-light (HL) stress compared to the wild type. We show that increased tolerance to HL of the mutant can be attributed to alterations in PSI, making it less prone to ROS production, thereby limiting oxidative damage and favoring growth in HL. HLR1 deficiency attenuates PSI light-harvesting capacity and growth of the mutant under light-limiting conditions. We conclude that HLR1, a member of a conserved and broadly distributed clade of LHCR proteins, plays a pivotal role in a dynamic balancing act between photoprotection and efficient light harvesting for photosynthesis.

Chlamydomonas mutant hpm91 lacking PGR5 is a scalable and valuable strain for algal hydrogen (H2) production

“…Together with the previous finding of higher activity of ROS-scavenging enzymes in hpm91 (Chen et al, 2016), we conclude that the lower amount of ROS observed in hpm91 (Fig. 2C and D) could be attributed to the marked increase of both protein abundance of those and activity of the ROS-scavenging enzymes as well as putatively reduced PSI antenna mentioned above (Lu et al, 2021). A question rises how this is elicited in the PGR5-lacking mutants.…”

Scaling-up and proteomic analysis reveals photosynthetic and metabolic insights toward prolonged H2 photoproduction in Chlamydomonas hpm91 mutant lacking proton gradient regulation 5 (PGR5)

“…2), we suggest that the lower amount of ROS observed in hpm91 (Fig. 2c and d) could be largely attributed to the marked increase of both protein abundance of those and activity of the ROS-scavenging enzymes as well as putatively reduced PSI antenna mentioned above (Lu et al 2021). A question is open how this is fulfilled in the mutant cells.…”

Regulation of Photosynthesis in Bloom-Forming Cyanobacteria with the Simplest β-Diketone

“…For example, how cyanobacteria evolved the ability to oxidize H 2 O and produce O 2 through photosynthesis is currently under discussion. ,− The gated two-electron-transfer mechanism for the electron transport from Q A to Q B and the evolutionary role of bicarbonate in this process remain to be fully explored . Even the precise contributions of the known components in the photosystems need to be further evaluated. , The interactions between AA and the photosynthetic proteins suggest a possible way to regulate the photosynthetic electron transport, which may also provide important hints for the design of artificial photosynthesis. , …”