Seminars and Events

Past Events

Category Seminar
Date and Time 2008-02-01 17:00 - 18:00
Venue Auditorium C1F
Speaker David J. Miller
Affiliation Comparative Genomics Centre, James Cook University, Australia
Title Genome evolution and the origins of the innate immune repertoire: insights from the coral Acropora and other “lower” animals
Poster click here to download(PDF)
Host Hiroshi Tarui
Summary With perhaps as few a a dozen different cell types, anthozoan cnidarians, a
group which includes corals and sea anemones, are amongst the simplest true
animals at the morphological level. However, in terms of the total number
and types of genes they are comparable with the most complex of animals -
the vertebrates. The coral genome contains a large number of genes once
thought of as vertebrate-specific, including clear homologs of many key
components of the vertebrate innate immune repertoire; considerable effort
is presently being directed into exploring the roles of these in combating
coral disease. Anthozoan genomes also contain a significant number of
"non-metazoan" genes - genes only previously known from members of the
other kingdoms of life. These are not the products of recent lateral gene
transfers, but long-term residents of cnidarian genomes that potentially
increase the biochemical complexity of the organism. The unexpected
complexity and heterogeneity of the coral transcriptome represents a major
challenge in understanding the functional biology of corals; essentially,
one cannot predict how corals will respond based on what is known about
other animals.

Many of the key genes and pathways of vertebrate immunity appear to have
much earlier origins than has been assumed previously and are represented in
the genomes of the coral and sea-anemone. Surveys of recently released
whole-genome sequences and large EST (expressed sequence tag) datasets imply that both the canonical Toll/Toll-like receptor (TLR) pathway and a
prototypic complement-effector pathway, involving C3 and several membrane
attack complex–perforin proteins, are present in corals and sea anemones,
members of the basal phylum Cnidaria. However, both pathways are likely to
have degenerated substantially in Hydra, leaving open the molecular
mechanism by which antimicrobial activities are induced in this textbook
cnidarian. Surprisingly, the cnidarian genomes also encode a protein related
to deuterostome RAG1 (recombination activation gene 1). The finding that
RAG1 is likely to have originated from a Transib transposase implies that it
might be possible to use in silico approaches to identify its target loci in
'lower' animals.