Salas Briana Hauff, Haslun Joshua A, Strychar Kevin B, Ostrom Peggy H, Cervino James M
University of Texas School of Medicine, San Antonio, TX, United States of America.
Michigan State University, Department of Integrative Biology, East Lansing, MI, United States of America.
PLoS One. 2017 Mar 29;12(3):e0173350. doi: 10.1371/journal.pone.0173350. eCollection 2017.
Scleractinian coral are experiencing unprecedented rates of mortality due to increases in sea surface temperatures in response to global climate change. Some coral species however, survive high temperature events due to a reduced susceptibility to bleaching. We investigated the relationship between bleaching susceptibility and expression of five metabolically related genes of Symbiodinium spp. from the coral Porites astreoides originating from an inshore and offshore reef in the Florida Keys. The acclimatization potential of Symbiodinium spp. to changing temperature regimes was also measured via a two-year reciprocal transplant between the sites. Offshore coral fragments displayed significantly higher expression in Symbiodinium spp. genes PCNA, SCP2, G3PDH, PCP and psaE than their inshore counterparts (p<0.05), a pattern consistent with increased bleaching susceptibility in offshore corals. Additionally, gene expression patterns in Symbiodinium spp. from site of origin were conserved throughout the two-year reciprocal transplant, indicating acclimatization did not occur within this multi-season time frame. Further, laboratory experiments were used to investigate the influence of acute high temperature (32°C for eight hours) and disease (lipopolysaccharide of Serratia marcescens) on the five metabolically related symbiont genes from the same offshore and inshore P. astreoides fragments. Gene expression did not differ between reef fragments, or as a consequence of acute exposure to heat or heat and disease, contrasting to results found in the field. Gene expression reported here indicates functional variation in populations of Symbiodinium spp. associated with P. astreoides in the Florida Keys, and is likely a result of localized adaptation. However, gene expression patterns observed in the lab imply that functional variation in zooxanthellae observed under conditions of chronic moderate stress is lost under the acute extreme conditions studied here.
由于全球气候变化导致海面温度上升，石珊瑚正经历着前所未有的死亡率。然而，一些珊瑚物种因对漂白的敏感性降低而在高温事件中存活下来。我们研究了来自佛罗里达群岛近岸和离岸珊瑚礁的多孔鹿角珊瑚中，共生藻属的五种代谢相关基因的表达与漂白敏感性之间的关系。还通过在两个地点之间进行的为期两年的相互移植，测量了共生藻属对温度变化的适应潜力。离岸珊瑚碎片中共生藻属基因PCNA、SCP2、G3PDH、PCP和psaE的表达显著高于近岸珊瑚碎片（p<0.05），这一模式与离岸珊瑚漂白敏感性增加一致。此外，在为期两年的相互移植过程中，来自原生地的共生藻属的基因表达模式保持不变，这表明在这个多季节的时间框架内没有发生适应。此外，实验室实验用于研究急性高温（32°C，持续8小时）和疾病（粘质沙雷氏菌的脂多糖）对来自相同离岸和近岸多孔鹿角珊瑚碎片的五种代谢相关共生体基因的影响。珊瑚礁碎片之间的基因表达没有差异, 急性热暴露或热暴露与疾病共同作用也不会导致基因表达差异，这与在野外发现的结果形成对比。此处报道的基因表达表明，与佛罗里达群岛多孔鹿角珊瑚相关的共生藻属群体存在功能差异，这可能是局部适应的结果。然而，在实验室中观察到的基因表达模式表明，在这里研究的急性极端条件下，在慢性中度胁迫条件下观察到的虫黄藻功能差异消失了。
