Differential expression microarrays reveal candidate genes potentially associated with reproductive dysfunction of captive-reared prawn Penaeus monodon

The Black tiger prawn Penaeus monodon is an internationally significant aquaculture species. However, partial dependence on wild-caught broodstock, due to compromised fecundity in most captive-reared animals, remains a major constraint to industry development. Reproductive performance of captive-reared females is often characterised by longer latency period, lower egg production, egg hatch rates and post-larval survivorship compared with their wild-caught counterparts. Improved understanding of the cellular and associated molecular events occurring during penaeid ovarian maturation could therefore be fundamental to improving reproductive success of captive-reared animals. In support of other studies ( Brady et al., 2012) that focussed on non-ovarian tissues, this present study considered both gene expression and histological analyses of ovarian tissue (i.e. developing oocytes) and revealed differences between wild-caught and captive-reared P. monodon, including reduced lipid accumulation in oocytes of captive-reared animals. We have employed oligonucleotide microarray analysis to compare expression profiles of genes involved in ovarian maturation among wild-caught and captive-reared animals. Custom oligonucleotide microarrays were constructed and screened with transcripts derived from the ovary, cephalothorax and eyestalk from animals of all ovarian maturation stages. Ovarian maturation-related differential expression patterns were observed for 111 transcripts, with 53 transcripts displaying differential expression between wild-caught and captive-reared animals. Notably transcripts encoding vitellogenin — the major egg yolk protein precursor, and a lipid storage droplet protein (which we named pmLSD) which is involved in lipid accumulation, were found to have higher expression in wild-caught animals. pmLSD transcripts localise to pre-vitellogenic oocytes of wild-caught animals and the pmLSD protein is exclusively localised to the surface of lipid droplets of oocytes at vitellogenic and cortical rod stages. Our identification of differentially expressed genes, and in particular those encoding a PAT-family lipid storage droplet protein, pmLSD, may provide the molecular tools for further functional characterisation in prawns and improvement of reproductive success among captive-reared animals.