Expression levels of vitellogenin receptor (Vtgr) during ovarian development and association between its single nucleotide polymorphisms (SNPs) and reproduction-related parameters of the giant tiger shrimp Penaeus monodon

Identification of molecular markers linked to phenotypic parameters of reproduction is important and can be applied to domestication and selective breeding programs of the giant tiger shrimp (Penaeus monodon). In this study, the full-length cDNA and expression levels of P. monodon vitellogenin receptor (PmVtgr) during ovarian development in wild shrimp and association between its single nucleotide polymorphisms (SNPs) and reproduction-related parameters in domesticated shrimp were examined. PmVtgr was 5990 bp in length composing of an open reading frame (ORF) of 5832 bp deducing to a polypeptide of 1943 amino acids. PmVtgr was only expressed in ovaries but not in other tissues of female broodstock. The expression level of PmVtgr in premature ovaries of juveniles was significantly lower than in those of broodstock (P < 0.05). In intact broodstock, PmVtgr mRNA significantly increased in stage IV (mature) relative to stage I (previtellogenic) ovaries (P < 0.05). However, PmVtgr was comparably expressed at all stages of ovarian development in eyestalk-ablated shrimp (P > 0.05). In addition, SNPs in the PmVtgr gene segment of 14-month-old P. monodon (N = 64) were indirectly examined by PCR-SSCP. Significant relationships between different SSCP patterns of PmVtgr and important reproduction-related phenotypes (i.e. gonadosomatic index, GSI and ovarian weight) of P. monodon were found. Results were consistent when further tested against non-related 19-month-old shrimp (N = 54, P < 0.05). Representative 14-month-old shrimp exhibiting different SSCP genotypes of PmVtgr were cloned and sequenced (N = 10 for each SSCP pattern). SNP positions 126 (C → T), 226 (T → A), 441 (T → A), 477 (T → A), 499 (A → C), 500 (T → C), 519 (A → G), 540 (A → G), 545 (G → A), 614 (T → C) and 678 (A → C) of PmVtgr were significantly associated with GSI values of examined shrimp (N = 40).