Coral genome as large as human one

Coral has around the same number of genes as humans, Australian researchers have found, suggesting a more complex biochemistry than anyone thinks.

This surprising result, from analysing one of the most abundant species of Australian coral, also challenges long-held assumptions about how different organisms evolved.

Molecular geneticist Dr Eldon Ball, of the Australian National University and team will report their findings in the journal Trends in Genetics later this year.

The researchers have so far found 6000 genes in the Acropora coral, which the researchers say suggests the coral's entire genome contains around 20,000 genes.

"The coral seems to have about as many genes as we do," says Ball. "This is a real surprise to us."

Ball says the findings challenge the idea that the more complex an organism's form, the more genes are needed to code for its complexity.

"The classical thought was that because you and I are more complex than a jelly fish, we had evolved more genes," he says. "That looks like it isn't the case."

Despite the coral polyp's outwardly simple structure its genome suggests it is biochemically very complex, says Ball.

Coral, fruit flies, elephants
The researchers also found a number of genes in the coral and humans that are not in the fruit fly or nematode, both laboratory models for understanding how genes control animal development.

"If you find genes in coral and vertebrates but not in flies, unless we've got everything really cock-eyed, then it must have been in the common ancestor and the fly [and the nematode] must have lost those genes," Ball says.

He says this means that although the fruit fly has led to many useful studies, it is not representative of all animals and this has implications for understanding the evolution of genes and genome sizes.

"Don't get me wrong. It's still a very valuable organism," he says.

"It's just it was the genome that was sequenced first and we thought what holds for the fruit fly must hold for an elephant. And that's not the case."

He says the new findings suggest the common ancestor between humans and coral must had more genes and complex biochemistry than originally thought.

Which genes drive coral bleaching?
Ball says better understanding of the coral genome could also help scientists to research problems such as coral bleaching, in which the symbiotic algae that live in the coral are evicted or flee when the coral is stressed.

"Are the algae kicked out or do they leave because internal conditions in the coral are unfavourable?" says Ball.

"The genes are the basis for the biochemistry," he says. "This should help us to work out the biochemical basis for the algae to enter the coral, and for the algae to leave."

But right now, the team has only mapped a fraction of the coral's genes.

"It's like trying to solve a puzzle with only a quarter of the pieces," says Ball.

Ball and Professor David Miller of James Cook University in Townsville would like to complete the sequencing of the Acropora coral in a so-called Coral Genome Project.

They hope to get funding from the Australian Genome Alliance, a group of Australian researchers lobbying the federal government for a genomics fund.

Source: abc.net.au