Myrtle rust is caused by the invasive fungus Austropuccinia psidii and is incredibly infectious and physically devastating to Myrtaceae plants. The disease was first detected in New Zealand in 2017 and continues to spread rapidly across the country. The presence of the disease in Australia has already caused major declines in Myrtaceae populations (e.g., eucalyptus in Queensland) and now threatens New Zealand natives, including taonga species such as pōhutukawa, mānuka and rātā. Localized extinctions of myrtle plants have already begun to occur in New Zealand.
Transcriptomics by collaborators at the University of Queensland, Australia identified several proteins that are expressed in the early stages of A. psidii infection—a signature that they are important for successful infection of plant cells. In other fungi, these ‘effector proteins’ are known to manipulate the host plant immune system and steal host nutrients. Presently, the structure and functions of these effectors are unknown. It is hypothesized that the identified A. psidii effector proteins have similar characteristics to other fungal effectors. The aim is this research is to define the characteristics of the identified A. psidii effector proteins through structural and functional studies. Techniques including analytical ultracentrifugation, nuclear magnetic resonance, small angle x-ray scattering, and x-ray crystallography are some being used to characterise the A. psidii effectors. Their structural determination will vastly improve our knowledge of the mechanisms of A. psidii infection and may uncover methods to interfere with their function, making their characterisation critical to New Zealand and Australian biosecurity. The outcome of this research will be critical for developing methods for controlling and potentially preventing disease.