Molecular characterization of HTR4 gene and screening of growth-related SNP loci in Takifugu fasciatus.

[Objective] This study investigated molecular structure, expression characteristics and function of the HTRA gene in Takifugu fasciatus and explored the correlation between HTRA gene and puffer growth. [Method] The 3 UTR, 5 UTR and intermediate fragments of HTRA gene were separately amplified by segmental cloning, the full-length cDNA sequence was obtained after splicing, and bioinformatics analysis was performed. The expression pattern of the HTRA gene in 10 tissues including brain, kidney, liver, spleen, heart, ovary, midgut, gill, skin and muscle and 8 tissues of ovary at 5 different developmental stages (I -V)including brain, kidney, liver, spleen, heart, midgut, gill and muscle was analyzed by quantitative real-time PCR technology. Finally, Sanger sequencing was used to screen the SNP loci related to growth traits in the coding region of HTRA. [Result] The cDNA full-length sequence of HTRA gene in largemouth bass was 2 302 bp in length with a 1 170 bp open reading frame encoding 389 amino acids and 5 exons. The amino acid sequence alignment and phylogenetic tree analysis showed that T. fasciatus had the highest identity (99.53%) with Takifugu rubripes. Spatial structure of HTRi protein showed that it was conserved in fish. The HTRA gene was expressed in 10 different tissues. The highest expression level was in brain, followed by midgut, and the lowest expression was in muscle tissue. The HTRA gene was expressed in 8 different tissues of the ovary at five different developmental periods, with the highest expression in the IV period of ovarian development. A synonymous mutant SNP locus (c.1202 C>G) at 1 202 bp in exon A of the HTRA gene of T. fasciatus was screened and association analysis showed that the SNP loci had significant correlation (P< 0.05) with fatness in T. fasciatus. Individuals with CC genotype had higher fatness than others. [Conclusion] The HTRA gene played important roles in the growth and development of T. fasciatus. It can be used as a candidate gene and molecular maker for selection of new varieties. [ABSTRACT FROM AUTHOR]