Heat-shock Protein 70: Sequence and Expression Analysis in African Catfish Clarias gariepinus after Bacterial Infection and Stress Exposures

Heat-shock protein 70 (HSP70) is a member of the Heat-shock protein family that plays an important role in cellular homeostasis against various stressors in fish. This research aimed to identify the full length of cDNA sequence HSP70 in African catfish C. gariepinus and assessed its mRNA expression under various tissues and stress conditions. The cDNA was cloned and amplified using the polymerase chain reaction (PCR) followed by bi-directional sequencing. The mRNA expression was quantified using the real-time PCR (qPCR) method. A full-length ORF of C. gariepinus HSP70 cDNA was 1932 bp long, encoded 643 amino acids. Three signature sequences of the HSP70 family were detected in the predicted amino acid sequence. The C. gariepinus HSP70 showed the highest similarity in nucleotide and amino acid sequence (>90%) to HSP70 from other Siluriformes catfish species. The HSP70 mRNA was expressed in all tested tissues, with the highest expression found in the liver and spleen, followed by the intestine, heart, head-kidney, and gill. The C. gariepinus HSP70 expression was significantly induced generally after 6 hours of bacterial infection, transportation, heat shock, and high nitrite exposure. The results indicated that the HSP70 gene could serve as an early stress biomarker in C. gariepinus