PDF(Pubmed)
Abstract：
The thermal tolerance of symbiodiniacean photo-endosymbionts largely underpins the thermal bleaching resilience of their cnidarian hosts such as corals and the coral model Exaiptasia diaphana. While variation in thermal tolerance between species is well documented, variation between conspecific strains is understudied. We compared the thermal tolerance of three closely related strains of Breviolum minutum represented by two internal transcribed spacer region 2 profiles (one strain B1-B1o-B1g-B1p and the other two strains B1-B1a-B1b-B1g) and differences in photochemical and non-photochemical quenching, de-epoxidation state of photopigments, and accumulation of reactive oxygen species under rapid short-term cumulative temperature stress (26-40 °C). We found that B. minutum strains employ distinct photoprotective strategies, resulting in different upper thermal tolerances. We provide evidence for previously unknown interdependencies between thermal tolerance traits and photoprotective mechanisms that include a delicate balancing of excitation energy and its dissipation through fast relaxing and state transition components of non-photochemical quenching. The more thermally tolerant B. minutum strain (B1-B1o-B1g-B1p) exhibited an enhanced de-epoxidation that is strongly linked to the thylakoid membrane melting point and possibly membrane rigidification minimizing oxidative damage. This study provides an in-depth understanding of photoprotective mechanisms underpinning thermal tolerance in closely related strains of B. minutum.
摘要：
共生生物的光-内共生体的耐热性在很大程度上支撑了它们的cnidarian宿主如珊瑚和珊瑚模型的热漂白弹性，排骨扩张症。虽然物种之间的耐热性变化是有据可查的，同种菌株之间的变异研究不足。我们比较了由两个内部转录间隔区2谱（一个菌株B1-B1o-B1g-B1p和另外两个菌株B1-B1a-B1b-1g）代表的三个紧密相关的小麦草菌株的耐热性以及光化学和非光化学猝灭的差异，光色素的去环氧化状态，和在快速短期累积温度胁迫（26-40°C）下活性氧的积累。我们发现B.minutum菌株采用不同的光保护策略，导致不同的上限热容差。我们提供了以前未知的耐热性特征与光保护机制之间相互依赖性的证据，其中包括激发能量的微妙平衡及其通过非光化学猝灭的快速松弛和状态转变成分的耗散。更耐热的B.minutum菌株（B1-B1o-B1g-B1p）表现出增强的去环氧化，这与类囊体膜的熔点和可能的膜硬化密切相关，从而最大程度地减少了氧化损伤。这项研究提供了对紧密相关的B.minutum菌株的热耐受性的光保护机制的深入了解。
