Differential Mitochondrial Genome Expression of Three Sympatric Lizards in Response to Low-Temperature Stress

Abstract

Ecological factors related to climate extremes have a significant influence on the adaptability of organisms, especially for ectotherms such as reptiles that are sensitive to temperature change. Climate extremes can seriously affect the survival and internal physiology of lizards, sometimes even resulting in the loss of local populations or even complete extinction. Indeed, studies have shown that the expression levels of the nuclear genes and mitochondrial genomes of reptiles change under low-temperature stress. At present, the temperature adaptability of reptiles has rarely been studied at the mitochondrial genome level. In the present study, the mitochondrial genomes of three species of lizards, Calotes versicolor, Ateuchosaurus chinensis, and Hemidactylus bowringii, which live in regions of sympatry, were sequenced. We used RT-qPCR to explore the level of mitochondrial gene expression under low-temperature stress, as compared to a control temperature. Among the 13 protein-coding genes (PCGs), the steady-state transcript levels of ND4L, ND1, ATP6, and COII were reduced to levels of 0.61 ± 0.06, 0.50 ± 0.08, 0.44 ± 0.16, and 0.41 ± 0.09 in C. versicolor, respectively, compared with controls. The transcript levels of the ND3 and ND6 genes fell to levels of just 0.72 ± 0.05 and 0.67 ± 0.05 in H. bowringii, compared with controls. However, the transcript levels of ND3, ND5, ND6, ATP6, ATP8, Cytb, and COIII genes increased to 1.97 ± 0.15, 2.94 ± 0.43, 1.66 ± 0.07, 1.59 ± 0.17, 1.46 ± 0.04, 1.70 ± 0.16, and 1.83 ± 0.07 in A. chinensis. Therefore, the differences in mitochondrial gene expression may be internally related to the adaptative strategy of the three species under low-temperature stress, indicating that low-temperature environments have a greater impact on A. chinensis, with a small distribution area. In extreme environments, the regulatory trend of mitochondrial gene expression in reptiles is associated with their ability to adapt to extreme climates, which means differential mitochondrial genome expression can be used to explore the response of different lizards in the same region to low temperatures. Our experiment aims to provide one new research method to evaluate the potential extinction of reptile species in warm winter climates.

Mitochondrial Protein-Coding Gene Expression in the Lizard Sphenomorphus incognitus (Squamata:Scincidae) Responding to Different Temperature Stresses

“…At 4 • C, besides the decrease in transcript levels of Complex I (ND1, ND4) and Complex V (ATP8), Complex IV joined the regulatory process, but transcript levels of COIII increased. Similarly, we observed a rapid increase in transcript levels of COIII in A. chinensis after cold stress [27]. Low temperatures can disturb membrane structure and abundance of mitochondria, leading to the production of ROS [54].…”

“…Interestingly, mitochondrial Complex I was found to have regulatory functions at extremely low temperatures of 4 °C and 8 °C, suggesting that S. incognitus has evolved an energy metabolism adaptation to extreme environments by modifying the efficiency of NADH dehydrogenase. In a study of cold adaptation in Calotes versicolor (the oriental garden lizard), similar regulatory functions of Complex I were found [ 27 ].…”

“…Similarly, we observed a rapid increase in transcript levels of COIII in A . chinensis after cold stress [ 27 ]. Low temperatures can disturb membrane structure and abundance of mitochondria, leading to the production of ROS [ 54 ].…”

“…For example, after an extreme cold event at 4.4 °C, most lizards living in subtropical southern Florida were found frozen to death [ 26 ]. Additionally, in a study by He et al [ 27 ], Ateuchosaurus chinensis (Chinese short-limbed skink) collected from Guangzhou, Guangdong, China, experienced mortality under laboratory conditions at 4 °C. Additionally, we noticed that the regulatory mechanism of mitochondrial respiratory chain complexes varies with temperature fluctuations, thereby promoting metabolic reshaping under changing environmental temperatures [ 28 ].…”