Guan Wen-Zhi, Guo Dan-Dan, Sun Yi-Wen, Chen Jie, Jiang Xia-Yun, Zou Shu-Ming
Key Laboratory of Freshwater Aquatic Genetic Resources, Shanghai Ocean University, Huchenghuan Road 999, Shanghai, 201306, China.
Fish Physiol Biochem. 2017 Apr;43(2):641-651. doi: 10.1007/s10695-016-0318-z. Epub 2017 Jan 26.
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.
血红素加氧酶（HO）-1是一种细胞保护酶，可参与针对缺氧应激的细胞保护作用。在本研究中，我们克隆了缺氧敏感型团头鲂（Megalobrama amblycephala）中重复的HO-1a和HO-1b cDNA。HO-1a和HO-1b分别编码含272个氨基酸和246个氨基酸的肽段，它们的序列同一性较低，为55%。HO-1a和HO-1b mRNA由母体沉积在受精卵中，且这些mRNA在受精后8小时降至最低水平。两种mRNA在受精后12小时均显著（p<0.01）表达，并呈波动变化，但在受精后16小时后维持在较高水平。通过原位杂交，HO-1a和HO-1b mRNA在受精后12小时的胚胎中普遍表达。在受精后24小时和36小时，分别在后脑和中脑检测到HO-1b转录本，而HO-1a在受精后24小时主要转录于眼睛和内胚层，在受精后36小时主要转录于脑。在成年鱼中，HO-1a在心脏、肝脏、鳃、肾脏、脾脏和脑中大量表达，而HO-1b mRNA主要在肾脏中检测到。暴露于缺氧应激后，HO-1a和HO-1b mRNA在鳃和肝脏中均显著上调，但在脑中显著下调（p<0.01）。这些发现表明，重复的HO基因已经发生了分化进化，但在调节团头鲂对缺氧的反应中发挥着重叠的生物学作用。
