Transcriptional profiling of shell calcification in bivalves
Mollusc shells are unique adaptations that serve to protect the organisms that make
them, and are a defining feature of the phylum. However the molecular underpinnings
of shell forming processes are still largely unexplored. To further understand
mollusc shell formation, I studied three bivalve species in this project: the blue mussel
Mytilus edulis, the Pacifc oyster Crassostrea gigas, and the king scallop Pecten
maximus. While previous analyses of the shell proteomes showed species specificity,
transcriptomes of the mantle tissues revealed more commonalities. To reconcile
these dfferences, I studied dfferential gene expression in shell damage-repair experiments
and during the formation of the �rst larval shell, to produce a comprehensive
overview of shell formation processes. Expression data showed large biological variability
between individuals, requiring matched-pair experimental designs to detect
dfferential gene expression during shell repair. Loci dfferentially expressed during
shell repair and in the larvae encoded shell matrix proteins, transmembrane transporters,
and novel transcripts. A large number of shell matrix proteins, encoded in
dfferentially expressed loci, were common in all three species during shell formation,
indicating that shell forming proteins between dfferent species may be more
common than previously thought. Dfferential expression of transmembrane transporters
during shell repair indicated that the animals may be regulating bicarbonate
ions during shell formation. Finally, the experiments revealed novel transcripts, with
unknown annotations to public datasets, that may putatively be involved in shell
formation.