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Impaired photoprotection in Phaeodactylum tricornutum KEA3 mutants reveals the proton regulatory circuit of diatoms light acclimation
bioRxiv - Plant Biology Pub Date : 2021-09-16 , DOI: 10.1101/2021.09.06.459119
Claire Seydoux , Mattia Storti , Vasco Giovagnetti , Anna Matuszyńska , Erika Guglielmino , Xue Zhao , Cécile Giustini , Yufang Pan , Jhoanell Angulo , Alexander V. Ruban , Hanhua Hu , Benjamin Bailleul , Florence Courtois , Guillaume Allorent , Giovanni Finazzi

Diatoms are amongst the most successful clades of oceanic phytoplankton, significantly contributing to photosynthesis on Earth. Their ecological success likely stems from their ability to acclimate to changing environmental conditions, including e.g. variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum photosynthetic electron transfer (PET) capacity of via Non Photochemical Quenching (NPQ). While the molecular effectors of this process, as well as the role of the Proton Motive Force (PMF) in its regulation are known, the putative regulators of the PET/PMF relationship in diatoms remain unidentified. Here, we demonstrate that the H+/K+ antiporter KEA3 is the main regulator of the coupling between PMF and PET in the model diatom Phaeodactylum tricornutum. By controlling the PMF, it modulates NPQ responses at the onset of illumination, during transients and in steady state conditions. Under intermittent light KEA3 absence results in reduced fitness. Using a parsimonious model including only two components, KEA3 and the diadinoxanthin de-epoxidase, we can describe most of the feedback loops observed between PET and NPQ. This two-components regulatory system allows for efficient responses to fast (minutes) or slow (e.g. diel) changes in light environment, thanks to the presence of a regulatory Ca2+-binding domain in KEA3 that controls its activity. This circuit is likely finely tuned by the NPQ effector proteins LHCX, providing diatoms with the required flexibility to thrive in different ocean provinces.

中文翻译:

三角褐指藻 KEA3 突变体光保护受损揭示了硅藻光驯化的质子调节回路

硅藻是最成功的海洋浮游植物进化枝之一,对地球上的光合作用做出了重大贡献。它们的生态成功可能源于它们适应不断变化的环境条件的能力,包括可变光强度。硅藻在消散光能方面表现出色,超过了通过非光化学淬火 (NPQ) 的最大光合电子转移 (PET) 能力。虽然该过程的分子效应器以及质子动力 (PMF) 在其调节中的作用是已知的,但硅藻中 PET/PMF 关系的推定调节器仍未确定。在这里,我们证明了 H + /K +逆向转运蛋白 KEA3 是模型硅藻中 PMF 和 PET 之间耦合的主要调节因子三角褐指藻。通过控制 PMF,它可以在光照开始、瞬态和稳态条件下调节 NPQ 响应。在断断续续的光照下,KEA3 的缺失会导致适应性降低。使用仅包含两个成分 KEA3 和二二黄素脱环氧化酶的简约模型,我们可以描述在 PET 和 NPQ 之间观察到的大多数反馈回路。由于KEA3 中控制其活性的调节性 Ca 2+结合域的存在,这种双组分调节系统允许对光环境中的快速(分钟)或缓慢(例如,昼夜)变化做出有效响应。该回路可能由 NPQ 效应蛋白 LHCX 进行微调,为硅藻提供在不同海洋区域繁衍生息所需的灵活性。
更新日期:2021-09-19
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