IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Montpellier, France.
Department of Life Sciences, Ben-Gurion University, Eilat Campus, 84105, Be'er Sheva, Israel.
BMC Biol. 2022 Jul 26;20(1):167. doi: 10.1186/s12915-022-01371-7.
Chimeras are genetically mixed entities resulting from the fusion of two or more conspecifics. This phenomenon is widely distributed in nature and documented in a variety of animal and plant phyla. In corals, chimerism initiates at early ontogenic states (larvae to young spat) and results from the fusion between two or more closely settled conspecifics. When compared to genetically homogenous colonies (non-chimeras), the literature has listed ecological and evolutionary benefits for traits at the chimeric state, further positioning coral chimerism as an evolutionary rescue instrument. However, the molecular mechanisms underlying this suggestion remain unknown.
To address this question, we developed field monitoring and multi-omics approaches to compare the responses of chimeric and non-chimeric colonies acclimated for 1 year at 10-m depth or exposed to a stressful environmental change (translocation from 10- to 2-m depth for 48h). We showed that chimerism in the stony coral Stylophora pistillata is associated with higher survival over a 1-year period. Transcriptomic analyses showed that chimeras lose transcriptomic plasticity and constitutively express at higher level (frontload) genes responsive to stress. This frontloading may prepare the colony to face at any time environmental stresses which explain its higher robustness.
These results show that chimeras are environmentally robust entities with an enhanced ability to cope with environmental stress. Results further document the potential usefulness of chimeras as a novel reef restoration tool to enhance coral adaptability to environmental change, and confirm that coral chimerism can be an evolutionary rescue instrument.
嵌合体是由两个或多个同种生物融合而成的遗传混合实体。这种现象在自然界中广泛存在，并在各种动物和植物门中都有记载。在珊瑚中，嵌合现象始于早期个体发育阶段（幼虫到幼珊瑚），是由两个或多个紧密定居的同种生物融合而成的。与遗传同质的群体（非嵌合体）相比，文献中列出了嵌合体状态下的生态和进化优势，进一步将珊瑚嵌合体定位为一种进化拯救工具。然而，这一观点背后的分子机制尚不清楚。
为了解决这个问题，我们采用了现场监测和多组学方法，比较了在 10 米深度适应 1 年的嵌合体和非嵌合体群体的反应，或暴露于应激环境变化（从 10 米深度转移到 2 米深度 48 小时）。我们表明，硬珊瑚石珊瑚中的嵌合现象与 1 年内更高的存活率有关。转录组分析表明，嵌合体失去了转录组可塑性，并持续高水平表达（前置）对压力敏感的基因。这种前置可能使群体随时准备应对环境压力，从而解释了其更高的稳健性。
这些结果表明，嵌合体是具有增强应对环境压力能力的稳健实体。研究结果进一步证明了嵌合体作为一种新的珊瑚礁恢复工具的潜在用途，以增强珊瑚对环境变化的适应性，并证实了珊瑚嵌合体可以成为一种进化拯救工具。
