Oceanography Department, Faculty of Science, Alexandria University, Alexandria City, Egypt.
Animal and Fish Production Department, Faculty of Agriculture (Saba Basha), Alexandria University, Alexandria City, 21531, Egypt.
BMC Genomics. 2023 Aug 23;24(1):476. doi: 10.1186/s12864-023-09569-x.
Tilapia is one of the most essential farmed fishes in the world. It is a tropical and subtropical freshwater fish well adapted to warm water but sensitive to cold weather. Extreme cold weather could cause severe stress and mass mortalities in tilapia. The present study was carried out to investigate the effects of cold stress on the up-regulation of antifreeze protein (AFP) genes in Nile tilapia (Oreochromis niloticus). Two treatment groups of fish were investigated (5 replicates of 15 fish for each group in fibreglass tanks/70 L each): 1) a control group; the fish were acclimated to lab conditions for two weeks and the water temperature was maintained at 25 °C during the whole experimental period with feeding on a commercial diet (30% crude protein). 2) Cold stress group; the same conditions as the control group except for the temperature. Initially, the temperature was decreased by one degree every 12 h. The fish started showing death symptoms when the water temperature reached 6-8 °C. In this stage the tissue (muscle) samples were taken from both groups. The immune response of fish exposed to cold stress was detected and characterized using Differential Display-PCR (DD-PCR).
The results indicated that nine different up-regulation genes were detected in the cold-stressed fish compared to the control group. These genes are Integrin-alpha-2 (ITGA-2), Gap junction gamma-1 protein-like (GJC1), WD repeat-containing protein 59 isoform X2 (WDRP59), NUAK family SNF1-like kinase, G-protein coupled receptor-176 (GPR-176), Actin cytoskeleton-regulatory complex protein pan1-like (PAN-1), Whirlin protein (WHRN), Suppressor of tumorigenicity 7 protein isoform X2 (ST7P) and ATP-binding cassette sub-family A member 1-like isoform X2 (ABCA1). The antifreeze gene type-II amplification using a specific PCR product of 600 bp, followed by cloning and sequencing analysis revealed that the identified gene is antifreeze type-II, with similarity ranging from 70 to 95%. The in-vitro transcribed gene induced an antifreeze protein with a molecular size of 22 kDa. The antifreeze gene, ITGA-2 and the WD repeat protein belong to the lectin family (sugar-protein).
In conclusion, under cold stress, Nile tilapia express many defence genes, an antifreeze gene consisting of one open reading frame of approximately 0.6 kbp.
罗非鱼是世界上最重要的养殖鱼类之一。它是一种热带和亚热带淡水鱼，适应温暖的水，但对寒冷的天气敏感。极冷的天气会导致罗非鱼严重应激和大量死亡。本研究旨在探讨冷应激对尼罗罗非鱼（Oreochromis niloticus）抗冻蛋白（AFP）基因上调的影响。研究了两组处理鱼（每组 15 条鱼，每个组 5 个重复，每个鱼缸 70 升）：1）对照组；鱼在实验室条件下适应两周，整个实验期间水温保持在 25°C，用商业饲料（30%粗蛋白）喂养。2）冷应激组；除温度外，与对照组相同。最初，温度每 12 小时降低 1 度。当水温达到 6-8°C 时，鱼开始出现死亡症状。在这个阶段，从两组中取出组织（肌肉）样本。使用差异显示-PCR（DD-PCR）检测和表征暴露于冷应激的鱼的免疫反应。
结果表明，与对照组相比，冷应激鱼中检测到 9 种不同的上调基因。这些基因是整合素-α-2（ITGA-2）、缝隙连接γ-1 蛋白样（GJC1）、WD 重复蛋白 59 异构体 X2（WDRP59）、NUAK 家族 SNF1 样激酶、G 蛋白偶联受体-176（GPR-176）、肌动蛋白细胞骨架调节复合物蛋白 pan1 样（PAN-1）、旋涡蛋白（WHRN）、肿瘤抑制 7 蛋白异构体 X2（ST7P）和 ATP 结合盒亚家族 A 成员 1 样异构体 X2（ABCA1）。使用特定的 600bpPCR 产物对 II 型抗冻基因进行扩增，然后进行克隆和测序分析表明，鉴定的基因是 II 型抗冻基因，相似度为 70%至 95%。体外转录基因诱导分子量为 22kDa 的抗冻蛋白。抗冻基因 ITGA-2 和 WD 重复蛋白属于凝集素家族（糖蛋白）。
总之，在冷应激下，尼罗罗非鱼表达了许多防御基因，一个抗冻基因由大约 0.6kbp 的一个开放阅读框组成。
