Molecular Control of Coral Development

Dr Eldon Ball Dr David Hayward

Background: The Phylum Cnidaria, to which corals belong, is commonly believed to be the nearest outgroup to the rest of the Metazoa. Members of this phylum therefore provide a window on the genome of the common ancestor, since genes common to cnidarians and higher metazoans must have been present in that ancestor. Our work on the coral Acropora millepora began as a search for Hox genes orthologous to those that we had been studying in insects, but has grown considerably in breadth as we realised the opportunities presented by this system.

Numerous transcription factors are present in Acropora, many containing homeoboxes, but we have found no evidence for a Hox-like cluster of genes. In a related previous project Lauretta Grasso established that at least ten nuclear receptors are also present, more than double the number previously known from any cnidarian.
Most recently we have been characterizing Acropora genes involved in processes thought to separate the bilateral higher animals from corals and other cnidarians. We have established the presence and characterised the expression of the coral ortholog of decapentaplegic, a gene involved in determining the dorsal/ventral axis in higher metazoans. The expression of this gene is consistent with the possibility that instead of being radially symmetrical, and thus differing from the higher metazoans, the coral planula is actually bilaterally symmetrical. Similarly, the snail gene, often considered to be a mesodermal marker, is expressed in tissue in the process of invagination to form endoderm in Acropora. Thus at the molecular level there appears to be a blurring of the boundaries between radiality and bilaterality and between diploblast and triploblast.

Potential Projects: In order better to understand what genes are present in Acropora, and how they are deployed during development, we have now created a large library of ESTs from three developmental stages. These ESTs represent approximately 6000 genes, many of which were totally unexpected in a coral. These uncharacterized genes provide great scope for projects which can be tailored to the interests of a particular student. Genes of particular interest to us include cell cycle genes (in collaboration with Rob Saint), ion channel genes and neurotransmitter genes. However, we are happy to discuss any potential projects.

Techniques that you could Learn: Techniques that you could learn doing a project characterizing Acropora genes include searching molecular databases, designing PCR primers and carrying out PCR reactions of different sorts, cloning PCR products, screening cDNA and/or genomic libraries, sequencing and analysing nucleotide sequences, analysing the phylogenetic relationships of the genes sequenced using a variety of techniques, tissue in situ hybridisation, characterisation of differentially expressed genes and analysis of temporal and spatial protein expression patterns using antibodies.

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