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December 2022
I attended the 8th annual Stromlo Plant Pathology meeting (SPPM), hosted at the Australian National University (ANU). This meeting covers a wide range of topics in molecular plant-pathogen interactions (MPMI) and pathogen evolution, with strong representation from students and early career researchers.
The SPPM was initially formed as an opportunity for Australasian MPMI researchers to come together and discuss their research, locally, as they had found that they were only meeting as a community at international conferences. For the first few years, it was hosted in the ANU’s meeting rooms at Mount Stromlo. Mount Stromlo houses the ANU’s School of Astronomy and Astrophysics, as well as the Mount Stromlo Observatory. This was a beautiful location for a meeting the size of the SPPM (approximately 100 attendees), with amazing views of outer Canberra; however, it was quite isolated, which made it logistically difficult for the organisers and relatively difficult for the attendees to get to. The meeting is now housed at the main campus of the ANU, at the Research School of Biology (RSB). The ANU campus is also very picturesque, with many trees and wide-open green spaces surrounding the buildings, and so it is not too much of a loss not being at Mount Stromlo (… and there is a coffee shop in front of the RSB which helps!).
I attended this conference to present my research into effectors used during infection by the wheat pathogen Zymoseptoria tritici. I also took this opportunity to meet and sit and have long discussions with Australian and New Zealand collaborators who have been even more restricted in their recent travel than researchers in Europe. The Australasian MPMI community is quite small, and many of the researchers attend the SPPM. Therefore, it was a fantastic opportunity to have a range of discussions and maintain connections with this network of researchers.
I was not the only international attendee present at this meeting; the first talk was from Dr Mareike Moeller, from Oregon State University, discussing her work studying the expansion of DNA methylation DIM-1 genes in Z. tritici populations away from the centre of origin. Including Dr Moeller’s presentation, there were a number of talks on Z. tritici at the meeting, ranging from the study of the pathogen’s extracellular vesicles to screening and identification of Z. tritici resistance in wheat. I was particularly interested by ideas presented by Dr Lachlan Dow from CSIRO, discussing Z. tritici-wheat-microbiome interactions. Z. tritici is primarily controlled by fungicide application; however, this pathogen can rapidly evolve resistance. Therefore, the identification of additional methods of controlling the pathogen (for example, novel resistance or the identification of biocontrol agents) is vital. Dr Dow and colleagues performed a microbiome study of wheat to identify actinobacteria with anti-Z. tritici bioactivity. He included discussion of competition assays between isolates of the bacteria and Z. tritici to demonstrate that some could inhibit the growth of the pathogen. The end goal of the project is to hopefully identify a novel secondary metabolite (SM) from among the many biosynthetic gene clusters in these bacteria. To aid in achieving their goal, they included a transcriptomic analysis in parallel to the microbiome assay, in order to identify which gene clusters are actively expressed in wheat (narrowing the initial candidate list for SM gene clusters of interest).
Research into a range of other plant-pathosystems were discussed during the two days of the conference and much discussion was given towards pathogens’ use of effectors. Unsurprisingly, a hotly engaged topic was the use of AlphaFold structural predictions to assist researchers formulate hypotheses about their effectors of interest. There was good representation from structural biology researchers at the meeting, and so the pros and cons of these computational developments were a primary topic of discussion both during the sessions and during the breaks. Work presented by one such structural biologist, Dr Megan Outram, highlighted the continued importance of functional structural analysis of effectors. Dr Outram discussed solving the structure of the most recently cloned wheat stem rust effector AvrSr27 that AlphaFold currently is unable to predict correctly. She hypothesised this is due to its inability to place ligands in structures, such as the four zinc ions found within AvrSr27, and this remains an ongoing challenge for computational predictors like AlphaFold. Another effector story from a structural biology lab, was by Carl McCombe, a PhD candidate from the Williams Lab at ANU. Carl discussed the study of a nudix hydrolase effector as an RNA-decapping protein, which he was able to verify with downstream activity assays. RNA-decapping is important in regulating RNA for degradation. Carl showed that the activity of this effector results in the suppression of pathogen triggered immunity (measured by flg22-induced ROS-burst suppression), thereby linking its enzymatic activity to a putative role in suppressing host-immune responses.
Although the majority of the talks focussed of agricultural pathosystems, speakers also addressed the importance of pathogen research in other spheres. Some highlights include: 1) The development of a method to detect protein-protein interactions, in planta, by Dr Jian Chen from CSIRO, using a split transcription factor fusion system that enables expression of the RUBY reporter when the interactions occur; 2) Dr Donald Gardiner, from the University of Queensland, discussing research into the potential of RNAi to be used as a control method for rust pathogens, demonstrated by the inhibition of myrtle rust (a pathogen to recently invade Australia) during infection, by the topical application of dsRNA (homologous to specific fungal targets, such as EF1-a and beta-tubulin).
The SPPM is a fantastic small meeting that covers a lot of cutting edge MPMI research in a short time period. If any international researchers find themselves in Australia in December, they should definitely consider attending! There are discussions under way for the SPPM to have a year in Queenstown, New Zealand, in the near future, which would also be amazing (particularly if it is held during the ski season!).
Eli Thynne
Environmental Genomics Group (Stukenbrock Lab), CAU
