CSIRO Synthetic Biology Future Science Platform, Land & Water, Black Mountain, ACT 2601, Australia.
School of BioSciences, The University of Melbourne, Parkville, VIC 3010, Australia.
Sci Adv. 2020 May 13;6(20):eaba2498. doi: 10.1126/sciadv.aba2498. eCollection 2020 May.
Coral reefs worldwide are suffering mass mortalities from marine heat waves. With the aim of enhancing coral bleaching tolerance, we evolved 10 clonal strains of a common coral microalgal endosymbiont at elevated temperatures (31°C) for 4 years in the laboratory. All 10 heat-evolved strains had expanded their thermal tolerance in vitro following laboratory evolution. After reintroduction into coral host larvae, 3 of the 10 heat-evolved endosymbionts also increased the holobionts' bleaching tolerance. Although lower levels of secreted reactive oxygen species (ROS) accompanied thermal tolerance of the heat-evolved algae, reduced ROS secretion alone did not predict thermal tolerance in symbiosis. The more tolerant symbiosis exhibited additional higher constitutive expression of algal carbon fixation genes and coral heat tolerance genes. These findings demonstrate that coral stock with enhanced climate resilience can be developed through ex hospite laboratory evolution of their microalgal endosymbionts.
全球范围内的珊瑚礁正遭受海洋热浪导致的大规模死亡。为了提高珊瑚对漂白的耐受性，我们在实验室中以 31°C 的高温对一种常见的珊瑚共生微藻进行了为期 4 年的 10 株克隆株的进化。所有 10 株经高温进化的菌株在实验室进化后都扩大了其体外的热耐受性。在将这些共生藻重新引入珊瑚宿主幼虫后，其中 3 株经高温进化的共生藻也提高了共生体的漂白耐受性。尽管进化后的藻类产生的活性氧（ROS）水平较低，但这与藻类的耐热性有关，ROS 分泌减少本身并不能预测共生关系中的耐热性。更耐受的共生关系表现出额外的、更高的藻类碳固定基因和珊瑚耐热基因的组成型表达。这些发现表明，可以通过对其共生微藻进行离体实验室进化来开发具有增强气候适应能力的珊瑚种群。
