Our Immune Defenses May Have Evolutionary Origins In Corals

Brett Smith for redOrbit.com – Your Universe Online

Many biological processes have their roots in the very earliest stages of life’s evolutionary tree, and new research in the journal BMC Genomics indicates that part of our immune system comes from coral-like ancestors.

According to the study, molecular biologists at the ARC Centre of Excellence for Coral Reef Studies (CoECRS) have found genes in Acropora, or staghorn, corals which are responsible for a quick, strong immune response to the presence of bacteria – genetic material that is also found in mammals, including humans.

“It’s early days, but it certainly looks as if key aspects of our ability to resist bacteria are extremely ancient and may have been pioneered by the ancestor of corals – and then passed down to humans in our evolutionary lineage,” said co-author David Miller, CoECRS team leader and a James Cook University professor of molecular biology and biochemistry.

“Corals are constantly attacked by bacteria in their natural environment, and so have perfected very efficient defenses against them,” Miller said. “These defenses apparently work well enough to be preserved in mammals like us, and possibly in plants too.

“Certain animals in between us and coral, like roundworms and flies, seem to have lost these genes, but our line appears to have retained them,” he added.

The genetic material is comprised of three genes, known as GiMAPs, that have long been associated with anti-bacterial response in mammals.

In the study, Miller and a team of Australian colleagues exposed living colonies of Acropora to signature chemicals associated with bacteria and looked for a genetic response from the sea creatures.

“We were quite surprised at how rapidly and strongly these three genes in particular reacted to the presence of bacterial proteins,” Miller said. “It was spectacular.”

The team said their main goal was not to shed light on mammalian evolution, but to gain a better understanding of the fragile creatures’ immune systems, which have been under siege in recent years.

“By better understanding the basis of coral immunity we may first be able to understand what is causing this pandemic of coral diseases and how human activity is connected to it,” Miller said. “And second, this may lead us to better ways of managing our reefs that reduce the impact of disease, and give corals a better chance of survival during a period of major climatic and environmental change.”

Miller has also been involved in another study that aims to identify the molecular processes behind the formation of coral exoskeletons, which make up coral reefs.

“With the world’s oceans becoming more acidic due to man-made carbon dioxide emissions, the whole basis by which corals and other marine organisms form their skeletons and shells – known as calcification – is under threat,” Miller said.

“Many marine scientists fear that if the oceans become more acidic as we redouble fossil fuel use, many of these lifeforms will not be able to cope – and our coral reefs could literally dissolve before our very eyes,” he added.

Miller said his ongoing work is focusing on seeing if and how corals can cope with ocean acidification and other threats on their own.