β-thymosins are a family of highly conserved polar 5-kDa polypeptides present in high concentra-tions in almost every cell.It has multiple and diverse intracellular and extracellular functions in vertebrates.It has a potentially strong immune function and has not been studied in Symphysodon aquifasciatus.The experiment used comparative genomics and bioinformatics methods to identify the thymosin of Symphysodon aquifasciatus,gene and protein structure analysis, and phylogenetic analysis to explore the characteristics, evolution and function of the thymosin gene in S.aquifasciatus.Through comparing the genome of S.aquifasciatus with NCBI database to construct the phylogenetic tree.The full length of S.aquifasciatus gene was obtained by RACE-PCR,and its ex-pression in various tissues was studied by quantitative real-time PCR.Then,we examined the expression of the thymosin gene under pathogen stress.The results showed that the thymosin gene of the fish was identified as thymosin β Type 1, named dfTβ .The results of RACE-PCR showed that the full-length of dfTβ gene was 779 bp, which contained 303 bp open reading frame, encoding 100 amino acids, and 43 bp 5'non-coding re-gion, 433 bp 3'non-coding region.The results of phylogenetic evolution analysis showed that S.aquifasciatus β-Thymosin gathered with Archocentrus centrarchus.The qPCR results showed that thymosin was expressed in all fish tissues,with the highest expression in the intestine, skin and gills and the lowest expression in the head, head kidney and spleen.After the infection of Aeromonas hydrophila,dfTβ in the skin, head kidney and spleen of the colorful angelfish β1 were significantly up-regulated in a short period, and showed a trend of first rising and then falling with time, but the time of the highest up-regulation multiple in each tissue was different.The re-sults show that the dfTβ gene is involved in the immune response of the fish after being stimulated by the patho-gen,and its expression patterns are different, indicating that it may play different roles in different tissues and different stages of immunity.This study provides a theoretical basis for further revealing the mechanism of the thymosin family in fish immune systems.And it also provides the basis for developing related preparations.
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