Evaluating the Transcriptional Regulation of Six Major QTL Candidate Genes During Low Temperature Stress in Takifugu rubripes

Abstract

Takifugu rubripes are warm temperate fish, suggesting that the reduced seawater temperatures in winter are likely to have a substantial impact on their survival. Considering this, there is likely to be some industrial value in breeding extremely low-temperature tolerant varieties of this fish. Here, we evaluate the expression changes in six major QTL candidate genes (tacc2, fsip1, exoc4, arhgap44a, pde10a, and unc5b) in response to reduced temperature in an effort to understand cold tolerance in T. rubripes. The expression changes of these six genes in the liver, heart, and kidney were detected using real-time quantitative PCR. This study used three groups of 8-month-old fish, all from the same family established by our research group, exposed to three different temperature gradients, where 8 ℃ and 13 ℃ acted as the minimum in the low temperature groups and 18 ℃ acted as the minimum in the control group. Our results showed that all six genes were expressed at different levels across each of these three tissues at different temperatures. The relative expression of pde10a first increased and then decreased in all three tissues, whereas the relative expression of tacc2 and exoc4 were distinctly different in the liver, kidney, and heart at 8 ℃. In this case, these transcripts first decreased and then stabilized in the liver, increased and then stabilized in the kidneys, and increased and then decreased in the heart. The relative expression of unc5b was low in the liver and heart, but high in the kidney following a second week of low-temperature growth, whereas arhgap44a expression was slightly upregulated in the liver and stable in the kidney and heart. fsip1 expression demonstrated a downward trend in the liver but seemed to first increase and then decrease in the heart and kidney. Taken together, these results demonstrate that all six of these genes are differentially expressed in different tissues of T. rubripes, with these differences exhibiting dynamic changes with respect to tissue origin and temperature. In addition, this data clearly revealed a positive correlation between cold stress and the expression of these QTL candidate genes. Thus, we can conclude that these six QTL candidate genes may play a substantial role in the low temperature adaptation of T. rubripes. This is significant because although low temperature is known to be an important factor limiting the development of the industrial utility of T. rubripes, there are still relatively few reports describing their cold stress response. This study provides a theoretical basis for the study of signaling pathways related to the low temperature tolerance response of T. rubripes and the development of low temperature tolerant varieties.

Keywords

• takifugu rubripes
• pde10a
• tacc2
• unc5b
• exoc4
• arhgap44a
• fsip1
• low temperature stress