Caferri Roberto, Zhou Qian, Dall'Osto Luca, Amelii Antonello, Shan Jianyu, Liu Zhenfeng, Bassi Roberto
Laboratory of Photosynthesis and Bioenergy, Department of Biotechnology, University of Verona, Verona, Italy.
State Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Nat Commun. 2025 Jul 26;16(1):6910. doi: 10.1038/s41467-025-62085-2.
Photosystem II (PSII) is the pigment-protein complex catalysing light-induced water oxidation. In Arabidopsis thaliana, it includes three Lhcb4-6 proteins linking the core complex to peripheral trimeric antennae. While Lhcb5 and Lhcb6 are encoded by single genes, Lhcb4 is encoded by three isoforms: Lhcb4.1 and Lhcb4.2, constitutively expressed, and Lhcb4.3 (Lhcb8), which accumulates under prolonged abiotic stress. Lhcb8 substitutes for Lhcb4, preventing Lhcb6 accumulation and resulting in a smaller PSII with high quantum yield. Cryo-electron microscopy reveals that Lhcb8 has a shorter carboxy-terminal domain, lacks two chlorophylls, and interacts more tightly with the PSII core, inducing structural changes in the PSII antenna system, ultimately inhibiting the formation of PSII arrays and favouring plastoquinone diffusion. We suggest that dynamic Lhcb4 vs Lhcb8 expression allows for PSII acclimation to contrasting light conditions, offering the potential for engineering crops with improved light use efficiency.
光系统II（PSII）是催化光诱导水氧化的色素-蛋白复合体。在拟南芥中，它包括三种将核心复合体与外周三聚体天线相连的Lhcb4-6蛋白。虽然Lhcb5和Lhcb6由单基因编码，但Lhcb4由三种亚型编码：组成型表达的Lhcb4.1和Lhcb4.2，以及在长期非生物胁迫下积累的Lhcb4.3（Lhcb8）。Lhcb8替代Lhcb4，阻止Lhcb6积累，导致具有高量子产率的较小PSII。冷冻电子显微镜显示，Lhcb8具有较短的羧基末端结构域，缺少两个叶绿素，并且与PSII核心的相互作用更紧密，诱导PSII天线系统的结构变化，最终抑制PSII阵列的形成并有利于质体醌扩散。我们认为，Lhcb4与Lhcb8的动态表达使PSII能够适应不同的光照条件，为培育具有更高光利用效率的作物提供了潜力。
