Expression of catechol O-methyltransferase during ovarian development and association between its SNP and reproduction-related parameters of the giant tiger shrimp Penaeus monodon

Abstract

Catechol O-methyltransferase cDNA and gene of the giant tiger shrimp Penaeus monodon (PmCOMT) were characterized. Genomic sequence of PmCOMT spanned 1466bp in length containing 3 exons (194, 111 and 361bp) and 2 introns (143 and 147bp). The full-length cDNA of PmCOMT was 1176bp in length with an open reading frame (ORF) of 666bp corresponding to a polypeptide of 221 amino acids. PmCOMT mRNA was not differentially expressed during ovarian development in wild intact P. monodon adults (P>0.05). Eyestalk ablation resulted in up-regulation of PmCOMT in stages II (vitellogenic) and IV (mature) relative to stage I (previtellogenic) ovaries (P<0.05). In domesticated shrimp, its expression was reduced in 18-month-old adults compared with 6-month-old juveniles and 14-month-old adults (P<0.05). In situ hybridization indicated that PmCOMT mRNA was clearly localized in ooplasm of previtellogenic oocytes but not in oogonia and other oocytes stages. Recombinant PmCOMT protein and anti-rPmCOMT polyclonal antibody were successfully produced. The PmCOMT protein was localized in ooplasm of previtellogenic oocytes. It was temporally found in both ooplasm and nucleus of vitellogenic oocytes and subsequently in cortical rods (Crs) and the Cr membrane of mature oocytes. In addition, single nucleotide polymorphism (SNP) in PmCOMT of domesticated P. monodon (14-month-old shrimp, N=64) was identified by single-strand conformational polymorphism (SSCP) and PCR-direct sequencing. Two SSCP patterns (A and B) corresponding to G/Cc.305+g.84 and C/Cc.305+g.84 SNP genotypes were found. Shrimp carrying the former genotype (OW=0.92±0.37g and GSI=1.06±0.39%, N=31) had a greater average ovarian weight and GSI value than those carrying the latter genotype (OW=0.75±0.30g and GSI=0.86±0.32%, N=33) (P<0.05). Taken the information together, PmCOMT should play the functional role during ovarian development of P. monodon. Statement of relevanceReduced reproductive performance of the giant tiger shrimp Penaeus monodon in captivity prevents the potential application of domestication and selective breeding program for genetic improvement of this economically important species. Understanding molecular mechanisms controlling the development and maturation of ovaries/oocytes is essential for finding an approach to promote the reproductive maturation of P. monodon without the use of eyestalk ablation. Two kinds of O-methyltransferase (OMT) transcripts; farnesoic acid O-methyltransferase (FAMeT) and catechol O-methyltransferase (COMT) have been characterized in penaeid species. P. monodon FAMeT was differentially expressed during ovarian development and its SNPs showed association with ovarian weight of domesticated adults. Similarly, the expression profile of P. monodon COMT was examined and eyestalk ablation affected its expression level during vitellogenic and mature stages. Relationships between a SNP of P. monodon COMT and reproduction-related parameters (ovarian weight and GSI) were found.