Gene jumping discovery may hold clues to agricultural production

November 28, 2016

A gene discovery in a crop of Biserrulla may unlock secrets of agricultural productivityA newly discovered process that allows genes to jump between different species of bacteria promises to unlock secrets of disease, drug resistance and agricultural productivity.

The discovery resulted from the work of Murdoch University PhD students Timothy Haskett and Amanuel Bekuma, in collaboration with Dr Josh Ramsay of Curtin University.

Dr Ramsay, who co-supervises the two PhD projects, said the discovery has far reaching impacts for molecular science.

“This gene transfer process may help explain the spread of antimicrobial resistance as well as having huge implications for agriculture,” he said.

Dr Jason Terpolilli from Murdoch University, a co-supervisor of the students, said the discovery has immediate important implications for Australia’s $50 billion agriculture industry.

“This gene jumping process was observed in rhizobia, which are specialised bacteria that form a beneficial association with roots of legumes to get nitrogen from the air rather than needing fertilisers,” he said.

“Since our agricultural legumes all come from elsewhere in the world, their specialised rhizobia are not present in our soils, so farmers have to add the bacteria to the soil when the crop is first introduced.”

The researchers came across this phenomenon while studying the rhizobia associated with Biserrula pelecinus, a pasture legume introduced to Australia from the Mediterranean in the 1990s.

This crop is now widely grown in Western Australia and in parts of New South Wales to feed livestock and boost nitrogen levels in soils.

“To our surprise when testing the crop six years later, we found that there were genetically different strains of Biserrula rhizobia in the paddock,” he said.

“The only explanation for the new strains was that the original rhizobia had transferred their genes to a local species of bacteria living in the soil.

“We believe that if native bacteria are taking on the nitrogen-fixing genes, they are not working as effectively as the original strain with the legumes to fix the nitrogen. If we can find a way to stabilise the original rhizobia to stop gene transfer, this discovery could have major potential to improve agriculture in Australia and worldwide.”

Dr Terpolilli said the discovery of this complex gene transfer process will be used to investigate ways to improve the benefits of using legumes in farming systems through the management of bacteria which are added to the soil and those that occur there naturally.

“We’ve known for a long time that bacteria can transfer genes between species, but our research has shown the process may be a lot more complex than previously understood,” Dr Terpolilli said.

“Until now, we’ve only known that some bacteria can transfer genes that are present as single pieces in their DNA .

“In our investigations we found that the genetic material involved in fixing nitrogen had not only transferred, but, amazingly, chunks of DNA from different areas of the bacteria’s genome had managed to transfer in a coordinated manner,” he said.

“Our new discovery shows the gene transfer process can be much more complex and elegant where three different pieces of the DNA all join together and are transferred simultaneously.”

“This is the first discovery of such a complex mechanism for gene transfer and raises many exciting questions for our understanding of bacteria, both beneficial and pathogenic, that associate with plant and animal hosts.”

“We will now be looking at ways to stabilise the genes to prevent the transfer to the native bacteria.”

The paper has been published in the prestigious journal Proceedings of the National Academy of Sciences of the USA and can be read here.

The research was funded by the Grains Research and Development Corporation Australia and Australia Awards Africa.

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