Molecular characterization of OSR1 in Pinctada fucata martensii and association of allelic variants with growth traits

Odd-skipped related 1 (OSR1) from Pinctada fucata martensii (PmOSR1) was cloned in this study. PmOSR1 contained an open reading frame measuring 951 bp that encoded a polypeptide of 316 residues. Domain analysis also revealed that PmOSR1 had a typical ZnF_C2H2 domain, indicating high identity with OSR1 protein sequence from Crassostrea gigas (55.25%) and Mizuhopecten yessoensis (65.48%). The expression pattern analysis of PmOSR1 revealed its wide expression in the tissues and developmental stages. PmOSR1 also presented a higher expression in the fast-growing group and hybrid families than in the slow-growing group and inbred families. The polymorphism analysis of PmOSR1 revealed 45 single nucleotide polymorphisms (SNPs) in the genomic sequence, and association analysis presented four SNPs significantly associated with growth traits (namely, shell length, width, height, and shell weight; P < 0.05). Three SNPs out of the four SNPs were shaped as a haploblock, and haplotype AGT showed significantly higher growth traits than that of haplotype AACAA. Therefore, PmOSR1 could be used as a growth candidate gene for the selective breeding of P. f. martensii.