Fu Jian-Rong, Zhou Jie, Zhang Yan-Ping, Liu Li
Fisheries College, Guangdong Ocean University, Zhanjiang 524088, China.
Guangdong Laboratory of Southern Ocean Science and Engineering, Zhanjiang 524025, China.
Biology (Basel). 2022 Dec 9;11(12):1792. doi: 10.3390/biology11121792.
An increasing ecological phase shift from coral-dominated reefs to macroalgae-dominated reefs as a result of anthropogenic impacts, such as eutrophication, sedimentation, and overfishing, has been observed in many reef systems around the world. Ocean warming is a universal threat to both corals and macroalgae, which may alter the outcome of competition between them. Therefore, in order to explore the effects of indirect and direct exposure to macroalgae on the physiological, biochemical, and genetic expression of corals at elevated temperature, the coral and highly invasive green algae were chosen. Physiologically, the results exhibited that, between the control and direct contact treatments, the density and chlorophyll a content of zooxanthella decreased by 53.1% and 71.2%, respectively, when the coral indirectly contacted with the algae at an ambient temperature (27 °C). Moreover, the enzyme activities of superoxide dismutase (SOD) and catalase (CAT) in coral tissue were enhanced by interacting with algae. After an increase of 3 °C, the density and chlorophyll a content of the zooxanthella reduced by 84.4% and 93.8%, respectively, whereas the enzyme activities of SOD and CAT increased 2.3- and 3.1-fold. However, only the zooxanthellae density and pigment content decreased when was co-cultured with at 30 °C. Molecularly, different from the control group, the differentially expressed genes (DEGs) such as Rab family, ATG family, and Casp7 genes were significantly enriched in the endocytosis, autophagy, and apoptosis pathways, regardless of whether was directly or indirectly exposed to at 27 °C. Under thermal stress without algae interaction, the DEGs were significantly enriched in the microbial immune signal transduction pathways, such as the Toll-like receptor signaling pathway and TNF signaling pathway, while multiple cellular immunity (IFI47, TRAF family) and oxidative stress (CAT, SODC, HSP70) genes were upregulated. Inversely, compared with corals without interaction with algae at 30 °C, the DEGs of the corals that interacted with at 30 °C were remarkably enriched in apoptosis and the NOD-like receptor signaling pathway, including the transcription factors such as the Casp family and TRAF family. In conclusion, the density and chlorophyll a content of zooxanthella maintained a fading tendency induced by the macroalgae at ambient temperatures. The oxidative stress and immune response levels of the coral was elevated at 30 °C, but the macroalgae alleviated the negative effects triggered by thermal stress.
由于富营养化、沉积和过度捕捞等人为影响，全球许多珊瑚礁系统都出现了从以珊瑚为主的珊瑚礁向以大型藻类为主的珊瑚礁的生态相移不断增加的现象。海洋变暖对珊瑚和大型藻类都是一种普遍威胁，这可能会改变它们之间的竞争结果。因此，为了探究在高温下间接和直接接触大型藻类对珊瑚生理、生化和基因表达的影响，选用了珊瑚 和高度入侵性的绿藻 。生理上，结果表明，在对照和直接接触处理之间，当珊瑚在环境温度（27°C）下与藻类间接接触时，虫黄藻的密度和叶绿素a含量分别下降了53.1%和71.2%。此外，珊瑚组织中的超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的酶活性通过与藻类相互作用而增强。温度升高3°C后，虫黄藻的密度和叶绿素a含量分别降低了84.4%和93.8%，而SOD和CAT的酶活性分别增加了2.3倍和3.1倍。然而，当 在30°C下与 共培养时，只有虫黄藻密度和色素含量下降。分子层面，与对照组不同，无论 在27°C下是直接还是间接接触 ，Rab家族、ATG家族和Casp7基因等差异表达基因（DEGs）在内吞作用、自噬和凋亡途径中均显著富集。在没有藻类相互作用的热应激下，DEGs在Toll样受体信号通路和TNF信号通路等微生物免疫信号转导途径中显著富集，而多个细胞免疫（IFI47、TRAF家族）和氧化应激（CAT、SODC、HSP70）基因上调。相反，与在30°C下未与藻类相互作用的珊瑚相比，在30°C下与 相互作用的珊瑚的DEGs在凋亡和NOD样受体信号通路中显著富集，包括Casp家族和TRAF家族等转录因子。总之，在环境温度下，虫黄藻的密度和叶绿素a含量因大型藻类而呈逐渐下降趋势。珊瑚的氧化应激和免疫反应水平在30°C时升高，但大型藻类减轻了热应激引发的负面影响。
