Yuyama Ikuko, Higuchi Tomihiko, Mezaki Takuma, Tashiro Hisako, Ikeo Kazuho
Graduate School of Science and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan.
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan.
Front Physiol. 2022 Apr 11;13:806171. doi: 10.3389/fphys.2022.806171. eCollection 2022.
Algal symbionts of corals can influence host stress resistance; for example, in the Pacific Ocean, whereas (C-type) is generally dominant in corals, (D-type) is found in more heat-resistant corals. Thus, the presence of D-type symbiont likely increases coral heat tolerance, and this symbiotic relationship potentially provides a hint to increase the stress tolerance of coral-algal symbioses. In this study, transcriptome profiles of and -harboring (C-coral and D-coral, respectively) and algal photosystem functioning ( ) under bleaching conditions (high temperature and light stress) were compared. Stress treatment caused algal photoinhibition that the / value of Symbiodiniaceae was immediately reduced. The transcriptome analysis of corals revealed that genes involved in the following processes were detected: endoplasmic reticulum (ER) stress, mitophagy, apoptosis, endocytosis, metabolic processes (acetyl-CoA, chitin metabolic processes, etc.), and the PI3K-AKT pathway were upregulated, while DNA replication and the calcium signaling pathway were downregulated in both C- and D-corals. These results suggest that unrepaired DNA and protein damages were accumulated in corals under high temperature and light stress. Additionally, some differentially expressed genes (DEGs) were specific to C- or D-corals, which includes genes involved in transient receptor potential (TRP) channels and vitamin B metabolic processes. Algal transcriptome analysis showed the increased expression of gene encoding photosystem and molecular chaperone especially in D-type symbiont. The transcriptome data imply a possible difference in the stress reactions on C-type and D-type symbionts. The results reveal the basic process of coral heat/light stress response and symbiont-type-specific coral transcriptional responses, which provides a perspective on the mechanisms that cause differences in coral stress tolerance.
珊瑚的藻类共生体可影响宿主的抗逆性；例如，在太平洋，虽然（C型）共生体在珊瑚中通常占主导地位，但（D型）共生体存在于更耐热的珊瑚中。因此，D型共生体的存在可能会提高珊瑚的耐热性，这种共生关系可能为提高珊瑚 - 藻类共生体的抗逆性提供了线索。在本研究中，比较了分别含有（C型珊瑚和D型珊瑚）的珊瑚以及在漂白条件（高温和光照胁迫）下藻类光系统功能（ ）的转录组图谱。胁迫处理导致藻类光抑制，共生藻的 / 值立即降低。对珊瑚的转录组分析表明，检测到参与以下过程的基因：内质网（ER）应激、线粒体自噬、细胞凋亡、内吞作用、代谢过程（乙酰辅酶A、几丁质代谢过程等），并且PI3K - AKT通路在C型和D型珊瑚中均上调，而DNA复制和钙信号通路下调。这些结果表明，在高温和光照胁迫下，珊瑚中积累了未修复的DNA和蛋白质损伤。此外，一些差异表达基因（DEGs）是C型或D型珊瑚特有的，其中包括参与瞬时受体电位（TRP）通道和维生素B代谢过程的基因。藻类转录组分析表明，特别是在D型共生体中，编码光系统和分子伴侣的基因表达增加。转录组数据暗示C型和D型共生体在应激反应上可能存在差异。这些结果揭示了珊瑚热/光应激反应的基本过程以及共生体类型特异性的珊瑚转录反应，这为导致珊瑚抗逆性差异的机制提供了一个视角。
