Trichoplax genome sequenced -- 'rosetta stone' for understanding evolution

(PhysOrg.com) -- Yale molecular and evolutionary biologists in collaboration
with Department of Energy scientists produced the full genome sequence of
Trichoplax, one of nature's most primitive multicellular organisms,
providing a new insight into the evolution of all higher animals.

The findings reported in the online edition of the journal Nature show that
while Trichoplax has one of the smallest nuclear genomes found in a
multi-cellular creature, it contains signature sequences for gene regulation
found in more complex animals and humans. Further, it defines Trichoplax as
a branching point of animal evolution.

"Trichoplax placozoans are animals that have only four body cell types and
no structured organs. They represent descendents of the oldest multi-celled
animal, perhaps older even than sponges," said author Stephen Dellaporta,
professor of molecular, cellular and developmental biology at Yale.

This study shows that compared with the nuclear genome of humans that
contains 3 billion base pairs, Trichoplax has only 98 million. Earlier
sequencing work showed that the mitochondrial genome of Trichoplax is over
twice the size of those found in most animals with genes, introns and spacer
sequences like the most primitive organisms.