The findings, published in Nature Plants, provide unprecedented insight into the molecular structure that enables the pathogen to gain entry, bringing scientists a step closer to countering the pathogen and protecting vulnerable plant species.
The myrtle rust pathogen is an aggressive invader that has decimated natural ecosystems across Australia, causing widespread defoliation and death of numerous native species, including the iconic Australian Lilly Pilly and native guava. It has also had a significant impact on horticulture and plantation forests.
Associate Professor Tony Bacic from the Centre of Excellence in Plant Energy Biology and the University of Melbourne said the discovery of the molecular structure that the pathogen uses to manipulate the waxy surface of the leaves was a crucial breakthrough in understanding how it invades and spreads.
"Plants have a waxy cuticle that is made up of a complex mixture of fatty substances, and on top is a layer of epicuticular wax that covers the outermost surface of the leaves. Our study revealed how the myrtle rust produces enzymes to break down this protective cuticle and wax, allowing the pathogen to penetrate the leaf surface and infect the plant," Associate Professor Bacic said.
The researchers were able to identify two key enzymes known as cutinases and laccases that were responsible for breaking down the waxy cuticle. They used a variety of advanced imaging techniques, including atomic force microscopy and transmission electron microscopy, to visualise and analyse the molecular structure of the pathogen's interaction with the host plant's surface.
"Our findings have important implications for the management of the myrtle rust disease," Associate Professor Bacic said. "By understanding how the pathogen gains entry to the host plant, we can potentially develop new strategies to prevent or control infection. This could include developing targeted fungicides or biocontrol agents, or engineering plants with enhanced wax barriers to resist the pathogen."
The research team is now working to develop assays to screen for resistance to myrtle rust in different plant varieties, and to identify other potential targets for controlling the disease. They are also investigating the potential use of biological control agents to suppress the pathogen's spread and help protect vulnerable plant species and ecosystems.
