Manullang Cristiana, Hanahara Nozomi, Tarigan Ariyo Imanuel, Abe Yuko, Furukawa Mao, Morita Masaya
Sesoko Marine Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa, 905-0227, Japan.
BMC Genomics. 2025 Jan 14;26(1):36. doi: 10.1186/s12864-024-11194-1.
Rising seawater temperatures increasingly threaten coral reefs. The ability of coral larvae to withstand heat is crucial for maintaining reef ecosystems. Although several studies have investigated coral larvae's genetic responses to thermal stress, most relied on pooled sample sequencing, which provides population-level insights but may mask individual genotype variability. This study uses individual larval sequencing to investigate genotype-specific responses to heat stress and the selective pressures shaping their genomes, offering finer resolution and deeper insights.
This study investigates the larval response to heat stress before acquiring symbiotic algae, aiming to elucidate the relationship between coral genetic diversity and heat stress. Larvae sourced from eight Acropora digitifera colonies were subjected to ambient temperature (28 °C) and heat conditions (31 °C). The impact of heat stress on larval genetic diversity was assessed through sequencing. While overall genetic diversity, represented by π, did not significantly differ between the control and heat-exposed groups, Tajima's D differed, indicating different selective pressures in each group. The genomic regions under higher and lower Tajima's D were not broadly shared among control and head conditions, implying that selective pressures operated in distinctive manners. Many larval protein-coding sequences were identified in this genomic region, and the codon evolution of many of these genes showed signs of positive selection. These results highlight the complex selective pressures on coral larvae under different temperatures. The genes showing signs of positive selection in response to heat stress may have also been influenced by historical temperature fluctuations, as suggested by their association with loci identified during Acroporid speciation. These loci under codon-level positive selection during speciation highlight the potential role of genetic diversity in shaping adaptation to environmental changes over evolutionary timescales.
These findings underscore the significance of genetic diversity in coral reproduction for maintaining reef ecosystems. They also indicate that even minor heat stress can exert significant selective pressure, potentially leading to profound implications for coral reef ecosystems. This research is crucial for understanding the impact of rising seawater temperatures on coral reefs.
海水温度上升对珊瑚礁构成越来越大的威胁。珊瑚幼虫耐受高温的能力对于维持珊瑚礁生态系统至关重要。尽管有多项研究调查了珊瑚幼虫对热应激的遗传反应，但大多数研究依赖于混合样本测序，这种方法能提供群体水平的见解，但可能掩盖个体基因型的变异性。本研究采用个体幼虫测序来探究基因型特异性的热应激反应以及塑造其基因组的选择压力，提供了更精细的分辨率和更深入的见解。
本研究调查了共生藻类获取之前幼虫对热应激的反应，旨在阐明珊瑚遗传多样性与热应激之间的关系。从八个指状鹿角珊瑚群体采集的幼虫分别置于环境温度（28°C）和热环境（31°C）条件下。通过测序评估热应激对幼虫遗传多样性的影响。虽然以π表示的总体遗传多样性在对照组和热暴露组之间没有显著差异，但 Tajima's D 有所不同，表明每组存在不同的选择压力。对照组和热环境条件下 Tajima's D 较高和较低的基因组区域没有广泛共享，这意味着选择压力以独特的方式起作用。在该基因组区域鉴定出许多幼虫蛋白质编码序列，其中许多基因的密码子进化显示出正选择的迹象。这些结果突出了不同温度下珊瑚幼虫面临的复杂选择压力。对热应激表现出正选择迹象的基因可能也受到了历史温度波动的影响，这从它们与鹿角珊瑚物种形成过程中鉴定出的位点的关联中可以看出。这些在物种形成过程中处于密码子水平正选择的位点突出了遗传多样性在进化时间尺度上塑造对环境变化适应性方面的潜在作用。
这些发现强调了珊瑚繁殖中遗传多样性对于维持珊瑚礁生态系统的重要性。它们还表明，即使是轻微的热应激也会施加显著的选择压力，可能对珊瑚礁生态系统产生深远影响。这项研究对于理解海水温度上升对珊瑚礁的影响至关重要。
