Abstract
Variable and low egg quality is a major limitingfactor for the development of efficient aquaculture production.This stems from limited knowledge on the mechanisms underlyingegg quality in cultured fish. Molecular analyses, suchas transcriptomic studies, are valuable tools to identify themost important processes modulating egg quality. However,very few studies have been devoted to this aspect so far.Within this study, the microarray-based transcriptomic analysisof eggs (of different quality) of sea bass (Dicentrarchuslabrax) was performed. An Agilent oligo microarray experimentwas performed on labelled mRNA extracted from 16batches of eggs (each batch obtained from a different female)of sea bass, in which over 24,000 published probe arrays wereused. We identified 39 differentially expressed genesexhibiting a differential expression between the groups oflow (fertilization rate < 60 %) and high (fertilizationrate > 60 %) quality. The mRNA levels of eight genes werefurther analyzed by quantitative PCR. Seven genes were confirmedby qPCR to be differentially expressed in eggs of lowand high quality. This study confirmed the importance ofsome of the genes already reported to be potential molecularquality indicators (mainly rnf213 and irf7), but we also foundnew genes (mainly usp5, mem-prot, plec, cenpf), which hadnot yet been reported to be quality-dependent in fish. Theseresults suggest the importance of genes involved in severalimportant processes, such as protein ubiquitination, translation,DNA repair, and cell structure and architecture; theseprobably being the mechanisms that contribute to egg developmentalcompetence in sea bass.