Using described methods, we first checked the cellular DNA content for the cell cycle profile

pressed by interference mediated gene silencing. Shrimp surviving 84 hours post-infection have higher expression of lysozyme, C-type lectin, penaeidins, prophenoloxidase-1 and prophenoloxidase-2 in haemocytes than those dying less than 60 hours post infection. Heat shock protein 21 is down regulated after infection to WSSV. Shrimp lysozyme has been shown to be effective in blocking infection by WSSV in blue shrimp . As yet there are no vaccines or other treatments available with proven efficacy against WSSV, although a number of studies have revealed promising leads. The WSSV binding proteins isolated from viral particles in the haemolymph of shrimp infected with WSSV, have been shown to inhibit the binding of this virus to haemolymph cells and improve survival of shrimp. Injection of shrimp with recombinant fortilin after infection with WSSV, results in 80-100% survival and low levels of WSSV are detected, suggesting that fortilin inhibits viral replication. Fortilin is highly upregulated in haemolymph during the early phase of white spot infection. Injection with recombinant ferritin or lysozyme also results in protection to challenge with WSSV. Inoculation in feed with bacterially expressed double stranded RNA VP28 and vaccination with VP28 and recombinant VP292, as well as exposure to probiotics and beta1,3/1,6-glucans, have been shown to provide improved survivability. Shrimp immunity to WSSV was shown to be enhanced by intramuscular injection of oligodeoxynucleotides with Cytosine-Guanine motifs and Vibrio harveyi DNA. In addition, PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19802338 double stranded RNA of any type has been found to induce antiviral protection in shrimp. Interestingly, a gene designated as PmAV was isolated using differential display from viral resistant shrimp and was shown to have antiviral activity. Resistance to WSSV is a strong candidate trait for marker-assisted or genomic selection since it appears to have low heritability and has a negative correlation with another selected trait. The lack of reported quantitative trait loci associated with this trait may not be due to the lack of segregating genes for resistance, but could instead be due to the highly virulent nature of WSSV, challenge testing methods that do not deliver accurate resistant phenotypes and because marker resources do not sufficiently cover the genome. Another important factor in shrimp cultivation is sex determination. Female penaeid shrimps grow more rapidly than males and so mono-sex production of females would be advantageous for production. This could also be used to provide a level of genetic protection, hindering the replication of genetically superior stock. In penaeid shrimps, females are known to be heterogametic with sex determined by a WZ-ZZ chromosomal system. However, more detailed mapping studies are needed to find closely linked markers and genes associated with sex determination. If homogametic females can be easily identified there is potential to use them as parents to yield completely sexually uniform heterogametic female offspring. Although some markers associated with sex Robinson et al. BMC Genomics 2014, 15:731 http://www.biomedcentral.com/1471-2164/15/731 Page 3 of 21 HC-067047 web determination have been identified, little is known about candidate genes, mechanism or map regions associated with the sex of crustaceans. Here we undertake the first comprehensive genome scan for QTL associated with resistance to WSSV and for the sex-determining locus in P. monodon. A new WSSV challenge