Project Leader, Organisation

Anne Sawyer, University of Queensland




Objective 4.3 of the National Myrtle Rust Action Plan (MRAP) is to explore methods for resistance and control. Controls for agricultural pathogens e.g. resistant cultivars or fungicides, are inapplicable against myrtle rust in natural environments. RNA interference (RNAi) vaccines are an emerging crop protection platform effective against agricultural pathogens, including wheat and soybean rusts. RNA is sprayed onto plants to trigger RNAi, silencing genes of the targeted pathogen. This project will explore RNAi vaccines as a novel control for myrtle rust in natural populations of Decaspermum humile and Syzygium hodgkinsoniae (both Very High priority species, Objective 4.3.5 MRAP).

Objectives and impact

RNAi vaccines are a novel crop protection strategy with applicability in natural environments. Pathogen-specific double-stranded RNA (dsRNA), which is applied then absorbed by plants and/or pathogens, triggers RNAi silencing pathways on targeted genes. We plan to develop RNAi vaccines as a control for myrtle rust addressing four specific aims:

1: Develop dsRNAs targeting essential Austropuccinia psidii genes

2: Test the effectiveness of synthesised dsRNAs against Austropuccinia psidii

3: Investigate the uptake and movement of dsRNA in the plant and pathogen

4: Deliver an RNAi vaccine against myrtle rust

dsRNAs will be designed to target A. psidii genes ensuring there is no off-target complementarity. Established bioassays and qPCR will be used to test RNA absorption by the plants and pathogen, efficacy of the targets and dose required for gene silencing. Uptake and movement of dsRNA in the plant and pathogen will be monitored using fluorescently-labelled dsRNA. Our preliminary work has found that A. psidii contains RNAi machinery and can take-up dsRNA, suggesting that RNAi vaccines could be effective.

This project uses new technology for plant resistance to protect Very High priority Australian species (NMRAP), with long-term benefits for conservation and biodiversity.