Croteau Dany, Jaubert Marianne, Falciatore Angela, Bailleul Benjamin
CNRS, Sorbonne Université, Institut de Biologie Physico-Chimique, Photobiologie et physiologie des plastes et des microalgues - P3M, Paris, France.
Nat Commun. 2025 Mar 10;16(1):2385. doi: 10.1038/s41467-025-57298-4.
Studies of marine microalgal photosynthesis are heavily moulded on legacy research from organisms like Arabidopsis and Chlamydomonas, despite the differences between primary and secondary endosymbionts. Non-photochemical quenching (NPQ) protects photosystem II from excessive light and, in pennate diatoms, requires the xanthophyll pigment diatoxanthin and Lhcx proteins. Although NPQ's relationship with diatoxanthin is straightforward, the role of Lhcx proteins has been unclear and at the core of several conflicting NPQ models, often unnecessarily borrowing the complexity of models from green organisms. We use 14 Phaeodactylum tricornutum strains, including 13 transgenic lines with variable Lhcx1 expression levels, grow them under two non-stressful light conditions, and modulate diatoxanthin levels through short light stress. The resulting Lhcx1-diatoxanthin matrices are used to demonstrate that NPQ is proportional to the product of the Lhcx1 concentration and the proportion of diatoxanthin in the xanthophyll pool. This indicates that the interaction between diatoxanthin and Lhcx1 creates a homogeneous Stern-Volmer quencher responsible for NPQ. Additionally, we demonstrate that the photosynthetic unit in pennate diatoms follows a "lake" model, with discrepancies in the NPQ-photochemistry relationship arising from unconsidered assumptions, one possibility being cellular heterogeneity. This underscores pennate diatoms as natural reductionist system for studying marine photosynthesis.
尽管初级和次级内共生体之间存在差异，但海洋微藻光合作用的研究很大程度上是基于拟南芥和衣藻等生物的传统研究。非光化学猝灭（NPQ）可保护光系统II免受过度光照，在羽纹硅藻中，这需要叶黄素色素二异岩藻黄素和Lhcx蛋白。虽然NPQ与二异岩藻黄素的关系很直接，但Lhcx蛋白的作用一直不清楚，并且是几个相互冲突的NPQ模型的核心，这些模型常常不必要地借鉴了绿色生物模型的复杂性。我们使用了14种三角褐指藻菌株，包括13种Lhcx1表达水平可变的转基因株系，在两种非胁迫光照条件下培养它们，并通过短暂的光照胁迫来调节二异岩藻黄素水平。由此得到的Lhcx1-二异岩藻黄素矩阵用于证明NPQ与Lhcx1浓度和叶黄素池中二异岩藻黄素比例的乘积成正比。这表明二异岩藻黄素和Lhcx1之间的相互作用产生了一个负责NPQ的均匀的斯特恩-沃尔默猝灭剂。此外，我们证明羽纹硅藻中的光合单位遵循“湖泊”模型，NPQ-光化学关系中的差异源于未考虑的假设，其中一种可能性是细胞异质性。这突出了羽纹硅藻作为研究海洋光合作用的天然简化系统。
