Mitochondrial OXPHOS genes provides insights into genetics basis of hypoxia adaptation in anchialine cave shrimps
Cave shrimps from the genera Typhlatya, Stygiocaris and Typhlopatsa (TST complex) comprises twenty cave-adapted taxa, which mainly occur in the anchialine environment. Anchialine habitats may undergo drastic environmental fluctuations, including spatial and temporal changes in salinity, temperature, and dissolved oxygen content. Previous studies of crustaceans from anchialine caves suggest that they have possessed morphological, behavioral, and physiological adaptations to cope with the extreme conditions, similar to other cave-dwelling crustaceans. However, the genetic basis has not been thoroughly explored in crustaceans from anchialine habitats, which can experience hypoxic regimes. To test whether the TST shrimp-complex hypoxia adaptations matched adaptive evolution of mitochondrial OXPHOS genes. The 13 OXPHOS genes from mitochondrial genomes of 98 shrimps and 1 outgroup were examined. For each of these genes was investigated and compared to orthologous sequences using both gene (i.e. branch-site and Datamonkey) and protein (i.e. TreeSAAP) level approaches. Positive selection was detected in 11 of the 13 candidate genes, and the radical amino acid changes sites scattered throughout the entire TST complex phylogeny. Additionally, a series of parallel/convergent amino acid substitutions were identified in mitochondrial OXPHOS genes of TST complex shrimps, which reflect functional convergence or similar genetic mechanisms of cave adaptation. The extensive occurrence of positive selection is suggestive of their essential role in adaptation to hypoxic anchialine environment, and further implying that TST complex shrimps might have acquired a finely capacity for energy metabolism. These results provided some new insights into the genetic basis of anchialine hypoxia adaptation.
KeywordsHypoxia Positive selection Mitochondrial OXPHOS Cave shrimps
Financial support was provided by the National Natural Science Foundation of China (Grant No. 31702014), the Doctoral Scientific Research Foundation of Yancheng Teachers University to ZFW, the Open Foundation of Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection (Grant No. JLCBE14008), and the Open Foundation of Jiangsu Key Laboratory for Bioresources of Saline Soils (Grant No. JKLBS2016007).
HYG, TYT and ZFW designed and conceived the experiment. BPT, ZFW, DT, HY and QW performed the data analysis and draft the manuscript. All authors read and approved the final manuscript.
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Conflict of interest
Huayun Guo declares that she has no conflict of interest. Hao Yang declares that he has no conflict of interest. Yitao Tao declares that he has no conflict of interest. Dan Tang declares that she has no conflict of interest. Qiong Wu declares that she has no conflict of interest. Zhengfei Wang declares that he has no conflict of interest. Boping Tang declares that he has no conflict of interest.
This article does not contain any studies with human subjects or animals performed by any of the authors.