maxima and P. margaritifera

and, b) determine which of these genes originate from the host and/or donor oyster. Our study found 19 of the 188 putative molluscan biomineralisation genes to be expressed within the pearl sacs of P. maxima and P. margaritifera. For the first time, we also showed that the majority of biomineralisation gene transcripts are derived from the mantle tissue of donor oysters used in the pearl seeding. This suggests that the donor oyster is the main genetic contributor to the secretion of the necessary regulatory proteins governing pearl formation. This study presents the first comprehensive sequencing effort Trichostatin A in vitro of a pearl sac for a pearl producing species. Through the use of high throughput Illumina GAII pyrosequencing we were able to examine for the first time 188 Selleck Imatinib putative biomineralisation genes expressed in the pearl sacs of P. maxima and P. margaritifera at pearl harvest and therefore potentially contributing to the biomineralisation process of pearl formation. Previous to this study, the expression of only nine putative biomineralisation genes had been identified within the pearl sac of a pearl oyster species, Pinctada fucata (msi31, n16, nacrein, msi60, prismalin-14, aspein, EFCBP, ACCBP and n19). These studies

compared expression patterns of these shell matrix proteins showing differences in expression levels within the pearl sac and between the pearl sac and mantle tissue ( Inoue et al., 2009, Inoue et al., Phospholipase D1 2010 and Wang et al., 2009). In the present study, we found 19 putative biomineralisation genes similarly expressed in both species examined indicating little divergence in the biomineralisation processes of pearl formation between these two species. The closeness of these two species has been previously highlighted using nuclear internal transcribed

spacer markers ( Yu and Chu, 2006 and Yu et al., 2006). However, the present study is the first to highlight that the process of pearl formation may be very similar between these two species. All detectable biomineralisation genes were expressed by the donor oyster tissue. This clearly demonstrates that the original donor mantle tissue survives the immunological response from the host oyster and actively secretes some of the necessary biomineralisation proteins that govern pearl formation. This confirms at a molecular level previous studies that have shown phenotypically that the donor is the main contributor to pearl quality traits, in particular colour and nacre deposition rate (Wada and Komaru, 1996 and McGinty et al., 2010). For example, through the use of xenografts involving two species which produce distinctively different base-coloured pearls, P. maxima and P. margaritifera, it was conclusively shown that the donor oyster is responsible for the colour of a pearl ( McGinty et al., 2010).