Characterization of duplicated heme oxygenase-1 genes and their responses to hypoxic stress in blunt snout bream (Megalobrama amblycephala)

Abstract

The heme oxygenase (HO)-1 is a cytoprotective enzyme that can be involved in cytoprotection against hypoxia stress. In this study, we cloned duplicated HO-1a and HO-1b cDNAs in hypoxia-sensitive blunt snout bream (Megalobrama amblycephala). HO-1a and HO-1b encode peptides with 272 amino acids and 246 amino acids, respectively, and they share a low sequence identity of 55%. HO-1a and HO-1b mRNAs were maternally deposited in the zygote, and the mRNAs decreased to the lowest levels at 8 hpf. Both mRNAs were significantly (p < 0.01) expressed from 12 hpf and fluctuated but maintained a high level after 16 hpf. Using in situ hybridization, HO-1a and HO-1b mRNAs were ubiquitously expressed in embryos at 12 hpf. At 24 and 36 hpf, HO-1b transcripts were detected in the mid- and hindbrain, respectively, whereas HO-1a was mainly transcribed in the eyes and endoderm at 24 hpf and in the brain at 36 hpf. In adult fish, HO-1a was abundantly expressed in the heart, liver, gill, kidney, spleen, and brain, while HO-1b mRNA was detected mainly in the kidney. After exposure to hypoxic stress, both HO-1a and HO-1b mRNAs were upregulated significantly in the gill and liver but downregulated significantly in the brain (p < 0.01). These findings suggest that duplicated HO genes have evolved divergently and yet play overlapping biological roles in regulating the response to hypoxia in M. amblycephala.

Divergence of Genes Encoding CITED1 and CITED2 in Blunt Snout Bream (Megalobrama amblycephala) and Their Transcriptional Responses to Hypoxia

“…For the juvenile fish treatment, 30 juvenile blunt snout bream (150~160 g each) were randomly transferred into three 50 L tanks within a continuous flow system (10 individual per tank). After 1 week of acclimation, two groups were exposed to severe hypoxic DO conditions (DO = 1.0 ± 0.5 mg/L) for 4 h by nitrogen-filled manipulation and a control group was retained under normoxic DO conditions (DO = 7.0 ± 0.5 mg/L) (Guan et al, 2017 ). Another two parallels were set for the control and experimental groups, respectively.…”

Functional exploration of SNP mutations in HIF2αb gene correlated with hypoxia tolerance in blunt snout bream (Megalobrama amblycephala)

“…However, blunt snout bream is a hypoxia-sensitive species. A seasonal change in temperature or water quality that decreases the dissolved oxygen (DO) concentration in ponds would cause adverse effects in aquaculture (Guan et al, 2017). Therefore, it needs to breed new sh varieties with relatively higher hypoxia-tolerance.…”

The transcriptomic responses of blunt snout bream (Megalobrama amblycephala) to acute hypoxia stress alone, and in combination with bortezomib

“…Blunt snout bream production output was more than 7.6 × 10 5 tons in 2019 [ 5 ]. However, blunt snout bream is a hypoxia-sensitive species, so the large changes in temperature, weather and water quality that decrease the DO (dissolved oxygen) concentration in ponds would cause relatively higher deaths in aquaculture [ 6 ]. Therefore, there is a need to breed a new strain with relatively higher hypoxia tolerance.…”