Abundance of the maternal mRNAs Pou2 and Zorba and their relation to events in the embryonic development of Oncorhynchus mykiss (Walbum)

The quality of an oocyte can be defined by its potential to produce a normal and viable embryo. In Oncorhynchus mykiss (Walbaum), oocyte quality is highly variable under both natural and aquaculture conditions. To ensure the competitiveness and sustainability of rainbow trout farming, new tools are needed to evaluate oocyte potential. Considering that the abundance of certain maternal mRNAs incorporated during oogenesis can determine egg quality, the aim of the present study was to assess if significant differences existed in the abundances of the maternal mRNAs pou2 and zorba in low and high quality O. mykiss eggs. Analyses determined that survival until the end of gastrulation varied significantly between high and low quality egg batches, and significant correlations were established with posterior early development events. The abundance of pou2 and zorba transcripts varied between high and low quality groups, with higher relative expression recorded in the low quality group. Additionally, the abundances of these transcripts were significantly correlated with survival until blastopore closure, the earliest ontogenetic event evaluated as a quality attribute for this salmonid species. This correlation is supported by participations reported for both proteins in other teleost fish during embryonic development. These results form a basis for complementary studies and permit proposing maternal pou2 and zorba mRNA as potential markers for O. mykiss egg quality.