Search

Background: Hoplobatrachus rugulosus (Anura: Dicroglossidae) is distributed in China and Thailand and the former can survive substantially lower temperatures than the latter. The mitochondrial genomes of the two subspecies also differ: Chinese tiger frogs (CT frogs) display two identical ND5 genes whereas Thai tiger frogs (TT frogs) have two different ND5 genes. Metabolism of ectotherms is very sensitive to temperature change and different organs have different demands on energy metabolism at low temperatures. Therefore, we conducted studies to understand: (1) the differences in mitochondrial gene expression of tiger frogs from China (CT frogs) versus Thailand (TT frogs); (2) the differences in mitochondrial gene expression of tiger frogs (CT and TT frogs) under short term 24 h hypothermia exposure at 25 °C and 8 °C; (3) the differences in mitochondrial gene expression in three organs (brain, liver and kidney) of CT and TT frogs. Results: Utilizing RT-qPCR and comparing control groups at 25 °C with low temperature groups at 8 °C, we came to the following results. (1) At the same temperature, mitochondrial gene expression was significantly different in two subspecies. The transcript levels of two identical ND5 of CT frogs were observed to decrease significantly at low temperatures (P < 0.05) whereas the two different copies of ND5 in TT frogs were not. (2) Under low temperature stress, most of the genes in the brain, liver and kidney were down-regulated (except for COI and ATP6 measured in brain and COI measured in liver of CT frogs). (3) For both CT and TT frogs, the changes in overall pattern of mitochondrial gene expression in different organs under low temperature and normal temperature was brain > liver > kidney. Conclusions: We mainly drew the following conclusions: (1) The differences in the structure and expression of the ND5 gene between CT and TT frogs could result in the different tolerances to low temperature stress. (2) At low temperatures, the transcript levels of most of mitochondrial protein-encoding genes were down-regulated, which could have a significant effect in reducing metabolic rate and supporting long term survival at low temperatures. (3) The expression pattern of mitochondrial genes in different organs was related to mitochondrial activity and mtDNA replication in different organs. [ABSTRACT FROM AUTHOR]

The relationship of Matrona and Atrocalopteryx (Odonata: Calopterygidae) is still unclear. To better understand the phylogenetic relationship of Matrona and Atrocalopteryx, we sequenced and annotated two complete mitochondrial genomes of Matrona basilaris sampled from two different locations. The length of the two complete mitochondrial genomes of M. basilaris is 16,149 bp and 15,893 bp for the specimens collected in Jinhua, Zhejiang Province and Tianmushan, Zhejiang Province, China, respectively. The two mitochondrial genomes include the typical invertebrate set of 37 genes: 13 protein-coding genes (PGCs), 22 tRNA genes, and 2 rRNA genes. The nucleotide composition of the mitogenome is similar to other odonates with high content of A + T (68.9%) and all PCGs use ATN as the start codon. Tandem repeats were detected in the control regions of the two M. basilaris samples that accounted for the different sequence lengths of the mitochondrial genomes from the two locations. Finally, BI and ML phylogenetic analysis based on the concatenated nucleotide sequences of the 13 PCGs supported the conclusion that M. basilaris is a sister clade to Atrocalopteryx melli. [ABSTRACT FROM AUTHOR]