A WORLD-first glyphosate resistance mechanism that works in a similar way to how cancer patients develop drug resistant tumours, has been discovered by a team of international research partners, including the Australian Herbicide Resistance Initiative (AHRI).
The story started nearly a decade ago when an agronomist in Kununurra discovered a barnyard grass weed that wasn't responding to glyphosate.
The weed was tested and it was found that it was resistant to glyphosate, but none of the usual suspects were causing the problem, so the source of the resistance was unknown.
AHRI professor Stephen Powles said through further research, it was found that the barnyard grass plant had a pump which was very similar to pumps which operated in human cancer cells.
"In humans, it's been known for a long time that one of the ways a tumour can become resistant to anti-cancer drugs is pumps, called ABC transporters, on the membrane that pump the drug straight back out as soon as it comes in," Mr Powles said.
"The reason this barnyard grass was resistant to glyphosate is because it also has a pump sitting on the membrane, very similar to that which occurs in human cells, that pumps the glyphosate back out of the cells.
"These ABC transporters have never before been shown to give any form of herbicide resistance, so this is the first time it's ever been reported that ABC transporters can cause resistance to glyphosate."
The finding itself is fundamental research - an understanding of how plants can be resistant to a herbicide as powerful as glyphosate, but it is still unknown how or when that fundamental knowledge will lead to applied outcomes.
However, for researchers at AHRI, the next step will be to investigate annual ryegrass populations for ABC transporters, something which Mr Powles believes is very likely.
"There are lots and lots of ryegrass populations in Australia that are resistant to glyphosate and we will start to look for the pump in those populations and in other weeds," he said.
"I'm almost certain that we will find the ABC transporters in ryegrass - the knowledge doesn't exist until someone makes it, so now we know exactly what the gene is, we can easily design sensors that will enable us to quickly check large numbers of other plants.
"At the moment it's not evident what the applied outcome might be for us, but the applied outcome in human cancer cells is that new drugs are designed so the ABC transporters don't work on them and can't pump the drugs out."
With the finding being the first of its sort in the world, a paper on the research was published in the prestigious journal, Proceedings of the National Academy of Sciences (PNAS) of the United States of America.
Mr Powles said in his long career, including more than 300 research papers, this was only the second paper that he has had in the PNAS journal.
"This is right up there with one of the most satisfying discoveries I've made in my career," he said.
"I speculated and did some experiments 25 years ago trying to see if the pumps in human cancer cells were occurring in plants, but I never got any results.
"It turns out we just needed new technology to be able to investigate that, so it's very gratifying to prove something right that I speculated over two decades ago."
The research was made possible through an agreement with the Chinese government to host Chinese students at AHRI, with former visiting PhD scholar Lang Pan and AHRI researcher Qin Yu leading the project alongside Mr Powles.
Overall, the publication of the paper is a great example of international collaboration, with the authors coming from Western Australia, China and Ukraine.
