ARTICLES
We’ve Cracked the Cane Toad Genome, and That could help put
the Brakes on its Invasion
By Peter White, Alice Russo and Rick Shine
and then assembled these overlapping pieces to produce one of
the highest-quality amphibian genomes to date.
We deduced more than 90% of the cane toad’s genes using
technology that can sequence very long pieces of DNA. This
made the task of putting together the genome jigsaw much easier.
Toxic toads
The cane toad has achieved iconic status in Australia, with
a number Australians loving to hate the poisonous invasive
amphibian. This is a little unfair. It’s not the cane toad’s fault – it
was humans who decided to bring it to Australia.
Cane toads are on the march, but new genetic research could
slow them down. Michael Linnenbach
Our obsession with sugar in the 1800s led to the toad’s introduction
to many countries around the world. Wherever sugar cane was
planted, the cane toad followed, transferred from one plantation
to another plantation by landowners as the warty interlopers first
travelled from South America to the Caribbean and then on to
Hawaii and Australia.
We and our international colleagues have managed to decipher
the genetic code of the cane toad. The complete sequence,
published today in the journal 'GigaScience', will help us
understand how the toad can so quickly evolve to adapt to new
environments, how its infamous toxin works, and hopefully give
us new options for halting this invader’s march across Australia.
Unlike most other places to which the cane toad was introduced,
Australia lacks any native toads of its own. The cane toad’s
powerful poisons are deadly to many of our native species that
have never before encountered this amphibian’s arsenal. The
cane toad has therefore been subject to detailed evolutionary and
ecological research in Australia, revealing not only its impact, but
also its amazing capacity for rapid evolution. Within 83 years of
its introduction, cane toads within Australia have evolved a wide
range of modifications that affect their body shape, physiology
and behaviour.
Since its introduction into Queensland in 1935, the cane toad has
spread widely, and now occupies more than 1.2 million square
kilometres of Australia. It is fatally poisonous to predators such as
the northern quoll, freshwater crocodiles, ghost bats and several
species of native lizards and snakes.
Previous attempts to sequence the cane toad, by WA researchers
more than 10 years ago, were not successful, largely because
the existing technology could not assemble the genetic pieces
to create a genome, but thanks to new methods we have now
managed to succeed in piecing together the entire genetic
sequence.
For example, cane toads at the invasion front are longer-legged
and bolder than those in the long-colonised areas, and invest
less into their immune defences (for a summary, see Cane Toad
Wars by Rick Shine).
Our team also featured researchers from Portugal and Brazil. We
were working at UNSW at the Ramaciotti Centre for Genomics.
This centre has also played a key role in decoding the genomes
of other iconic Australian species, including the koala.
The new genome will give us insights into how evolution
transformed a sedentary amphibian into a formidable invasion
machine. Moreover, it could give us new weapons to help stop,
or at least slow, this invasion.
Sequencing, assembling and annotating a genome (working out
which genes go where) is a most complicated process. The cane
toad genome is similar in size to that of humans, at roughly 3
billion DNA “letters”. By using cutting-edge technology, our team
sequenced more than 360 billion letters of cane toad DNA code,
url of video: https://youtu.be/aJF_C6c_f8U
Cracking the cane-toads’ DNA
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SCIENCE EDUCATIONAL NEWS VOL 67 NO 4