Molecular characterisation of biomineralising genes in the freshwater pond snail Lymnaea stagnalis
by Ines Herlitze
Date of Examination:2017-09-14
Date of issue:2018-06-22
Advisor:Prof. Dr. Daniel John Jackson
Referee:Prof. Dr. Daniel John Jackson
Referee:Dr. Frédéric Marin
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Abstract
English
Much of the evolutionary success of conchiferan molluscs can be traced back to the ability to construct a biocalcified shell that supports the soft molluscan body and offers protection from predation and desiccation. Only a small fraction of the shell is comprised of organic material, but these components play an important role in conferring the shells material properties and finally define shape, size and colour of the structure. Technical advances in nucleic acid sequencing and high-throughput proteomics promoted the identification of the proteinaceous components of the shell on the molecular level and enabled the collection of a large number of mineralising genes and proteins. Most studies focused on marine species with nacro-prismatic shells such as the pearl oyster Biomineralization and the abalone Haliotis. To get a better understanding of the shell secretome diversity, it is important to extend the research focus to species that compose microstructures other than narco-prismatic. In my thesis, I present the shell proteome of the crossed-lamellar type. To date, the functional characterisation of the proteinaceous shell components still represents a major challenge in the field of molluscan biomineralisation. I gained insight into the function of shell-forming genes by ontogenetically and spatially characterising the crossed lamellar shell proteome of the freshwater gastropod Lymnaea stagnalis. The expression showed patterns of asymmetry in the shell-forming cells of larvae and hint at the potential for interactions between co-expressed genes. They furthermore revealed that many adult shell-forming genes are already present in larvae, foreshadowing the zonation of the adult mantle. I furthermore analysed the genomic architecture and tissue specific expression patterns of these genes and propose that alternative splicing significantly contributes to the molecular diversity of the L. stagnalis shellome.
Keywords: Biomineralization; Shell-Formation; Mollusk; Evolution; Lymnaea stagnalis; Gastropod; in situ Hybridization