Fih attenuates the hypoxic tolerance of Megalobrama amblycephala by inhibiting the activity of hypoxia-inducible factor alpha (hif-α)

Abstract

Megalobrama amblycephala (Wuchang bream) is a widely farmed native species with the lowest hypoxic tolerance among the major aquaculture species in China. It is often threatened by hypoxic environments in aquaculture due to high culture densities and weather changes. Identification of the key genes and elucidation of the mechanisms involved in hypoxic tolerance provide the basis for genetic breeding of hypoxia-tolerant Megalobrama amblycephala strains. Here, we report that fih is evolutionarily conserved across species. CRISPR/Cas9-generated fih heterozygotes in Megalobrama amblycephala facilitate hypoxic tolerance and exhibit increased expression of hypoxia-responsive genes, including pdh3, glut1 and vegfa. Mechanistically, coimmunoprecipitation experiments indicated that overexpressed Megalobrama amblycephala fih (Ma-fih) interacts with the transcription factor hypoxia inducible factor (Ma-hif-α). Dual-luciferase assay showed that overexpression of Ma-fih inhibited the transcriptional activity of Ma-hif-α. In addition, we found that overexpression of Ma-fih suppressed hypoxia-induced glucose uptake in EPC cells. This study not only highlights the critical function of Ma-fih in regulating the hypoxia signaling pathway, but also provides a candidate gene for breeding hypoxia-tolerant Megalobrama amblycephala strains.