Mytilus galloprovincialis: development of female gonads

Transcriptional profiling of the mantle tissue across the four stages of female gonads development (winter peak) in a natural population of the marine mussel Mytilus galloprovincialis sampled in the Bizerta Lagoon, Tunisia, across November 2007 -March 2008. Background: Seasonal environmental changes may affect the physiology of Mytilus galloprovincialis (Lam.), an intertidal filter-feeder bivalve occurring commonly in Mediterranean and Atlantic coastal areas. We investigated seasonal variations in relative transcript abundance of the digestive gland and the mantle (gonads) of males and females. To identify gene expression trends, we used a medium-density cDNA microarray (1.7 K probes) in dual-color competitive hybridization analyses. Results: Hierarchical clustering of digestive gland microarray data showed two main branches, distinguishing profiles associated with the “hot” months (May–August) from the other months. Genes involved in chitin metabolism, associated with mussel nutrition and digestion, showed higher expression during summer. Moreover, we found different gene expression patterns in the digestive glands of males and females during the four stages of mussel gonadal development. Microarray data from gonadal transcripts also displayed clear patterns during the different developmental phases with peak relative mRNA abundance at the ripe phase (stage III) for both sexes. Conclusion: These data showed a clear temporal pattern in gene expression profiles of mussels sampled over an annual cycle. Physiological response to thermal variation, food availability, and reproductive status across months may contribute to variation in gene expression. Mantle tissue from individual animals in different gonad maturation stages were analyzed in a complete loop design. Dual color competitive hybridizations (stage 4 vs stage 1, 2 vs 1, 3 vs 2, 4 vs 3) including label swap. Single individuals. Four biological replicates. One replicate per array.