Dr Susan Breen

Research

My research is aimed at understanding how plant pathogens manipulate host plants in order cause disease. Pathogens manipulate plant defence responses on multiple levels, suggesting complex exchanges of signals between host and pathogen. My plant pathogen of interest is the notorious oomycete pathogen Phytophthora infestans, the causal agent of the devastating potato late blight. P. infestans. 

P. infestans is a hemi-biotrophic pathogen which secretes a broad range of pathogenicity factors which includes an array of proteinaceous effectors, the main group of which is the RXLR (+/-EER) effectors. These effectors contain this conserved amino acid sequence and there are over 500 RXLR (+/-EER) effectors in P. infestans. Effectors are secreted from haustoria, finger-like projections that protrude into the plant cell making contact with the cell membrane, and RXLR effectors are translocated into host cells. Once inside the host cell these protein modify innate host systems in order to cause and enhance disease. Understanding what these effectors target and how they modify the host gives us some clues in order to help plants protect themselves against pathogen attack.

Understanding how these effectors are secreted and translocated into the host cell is a critical area of research in order to stop these protein making it across the cell membrane and into host cells. Inhibitor studies revealed that apoplastic effectors and other pathogenicity proteins were conventionally secreted while the RXLR effectors tested were secreted by a different pathway, non-conventionally secreted. We believe that these effectors are secreted out of the pathogen into the extrahaustorial matrix via extracellular vesicles (EVs). It has been shown that uptake of some RXLR effectors by plant cells involves clathrin-mediated endocytosis. Questions still being investigated are 1) what determines the cargo of EVs, 2)what triggers clathrin-mediated endocytosis and 3) how is the P. infestans cargo released, once endocytosed, allowing the RXLR effectors to function within the host cell.

Publications

The following Publications have not yet been migrated to the James Hutton Institute's Pure service and relate to the research outputs from the two legacy organisations: The Macaulay Land Use Research Institute and The Scottish Crop Research Institute.

Journals

1. Trupti Gaikwad*, Susan Breen*, Emily Breeze*, Erin Stroud et al (2026) Rapid local and systemic jasmonate signalling drives initiation and establishment of plant systemic immunity. Nature Plants. https://doi.org/10.1038/s41477-025-02178-4
2. Susan Breen*, Hazel McLellan*, Wei Wang* et al. (2025) Identification of MARVELlous Protein Markers for Phytophthora infestans Extracellular Vesicles. Journal of Extracellular Vesicles. https://doi.org/10.1002/jev2.70101
3. Yetong Qi, Jiahui Wu, Zhu Yang, Hongjun Li, Lang Liu, Haixia Wang, Xinyuan Sun, Xinya Wu, Jiahui Nie, Jing Zhou, Meng Xu, Xintong Wu, Susan Breen et al. (2024) Chloroplast elongation factors break the growth–immunity trade-off by simultaneously promoting yield and defence. Nature Plants. https://doi.org/10.1038/s41477-024-01793-x
4. Susan Breen et al (2023) Tuning the wavelength: Manipulation of light signalling to control plant defence. J. Mol. Sci. 2023, 24, 3803. doi.org/10.3390/ijms24043803
5. Susan Breen, et al. (2022) Chloroplasts play a central role in facilitating MAMP-triggered immunity, pathogen suppression of immunity and crosstalk with abiotic stress. Plant Cell and Environment, 1–17. https://doi.org/10.1111/pce.14408
6. Eleanor Gilroy and Susan Breen. (2022) Interplay between phytohormone signalling pathways in plant defence – other than salicylic acid and jasmonic acid. Essays in Biochemistry. https://doi.org/10.1042/EBC20210089
7. Haixia Wang, Franziska Trusch, Dionne Turnbull, Carolina Aguilera-Galvez, Susan Breen, et al., (2021) Evolutionarily distinct Resistance proteins detect a pathogen effector through its association with different host targets. New Phytologist, 232:1368–1381. DOI:1111/nph.17660.
8. Yi-Chang Sung*, Megan A. Outram*, Susan Breen, et al., (2021) PR1-mediated defence signalling via C-terminal peptide release is targeted by a fungal pathogen effector. New Phytologist, 229: 3467-3480.org/10.1111/nph.17128
9. George Littlejohn*, Susan Breen*, Nicholas Smirnoff and Murray Grant. (2021) Chloroplast immunity illuminated. New Phytologist, Invited Tansley Review, 229: 3088-3107. org/10.1111/nph.17076
10. Mariano Jordi Muria-Gonzalez, Yeannie Yeng, Susan Breen, et al., (2020) Volatile molecules secreted by the wheat pathogen Parastagonospora nodorum are involved in development and phytotoxicity. Frontiers in Microbiology, 11:466. DOI: 10.3389/fmicb.2020.00466
11. Dionne Turnbull*, Haixia Wang*, Susan Breen, et al., (2019) AVR2 target BSL1/2/3 as susceptibility factors that suppresses host immunity and enhances late blight disease. Plant Physiology, 180:571-581. DOI: https://doi.org/10.1104/pp.18.01143.
12. Jiapeng Chen*, Narayana M. Upadhyaya*, Diana Ortiz*, Jana Sperschneider, Feng Li, Clement Bouton, Susan Breen et al., (2017) Loss of AvrSr50 by somatic exchange in stem rust leads to virulence for Sr50 resistance in wheat. Science, 358(6370):1607-1610. DOI: 10.1126/science.aao4810
13. Susan Breen*, Simon J. Williams* Megan Outram, Bostjan Kobe, Peter S. Solomon. (2017) Emerging insights into the functions of pathogenesis-related protein 1. Trends in Plant Science, 22(10):871-879. DOI: http://dx.doi.org/10.1016/j.tplants.2017.06.013
14. Dionne Turnbull, Lina Yang, Shaista Naqvi, Susan Breen, et al., (2017) RXLR Effector AVR2 Up-Regulates a Brassinosteroid-Responsive bHLH Transcription Factor to Suppress Immunity. Plant Physiology, 174(1):356-369. DOI:10.1104/pp.16.01804.
15. Xiaoxiao Zhang*, Neal Nguyen*, Susan Breen, et al., (2017) Production of small cysteine-rich effector proteins in Escherichia coli for structural and functional studies. Molecular Plant Pathology, 18(1): 141-151. DOI: 10.1111/mpp.12385
16. Susan Breen Simon J. Williams, Britta Winterberg, Bostjan Kobe, Peter S. Solomon. (2016) Wheat PR-1 proteins are targeted by necrotrophic pathogen effector proteins. The Plant Journal, 88(1): 13-25. DOI:10.1111/tpj.13228
17. Huyen T.T. Phan, Kasia Rybak, Eiko Furuki, Susan Breen et al., (2016) Differential effector gene expression underpins epistasis in a plant fungal disease. The Plant Journal, 87(4) 343-354. DOI:10.1111/tpj.13203
18. Susan Breen, Peter S. Solomon, Frank Bedon, and Delphine Vincent. (2015) Surveying the potential of secreted antimicrobial peptides to enhance plant disease resistance. Frontiers in Plant Science, 6:900. DOI: 10.3389/fpls.2015.00900
19. Mariano Jordi Muria-Gonzalez, Yit-Heng Chooi, Susan Breen, Peter S. Solomon. (2015) The past, present and future of secondary metabolite research in the Dothideomycetes. Molecular Plant Pathology, 16(1): 92–107 DOI: 10.1111/mpp.12162
20. Diane G O Saunders, Susan Breen et al., (2012) Host Protein BSL1 Associates with Phytophthora infestans RXLR Effector AVR2 and the Solanum demissum Immune Receptor R2 to Mediate Disease Resistance. The Plant Cell, 24: 3420-3434 DOI: 10.1105/tpc.112.099861
21. Eleanor M Gilroy, Susan Breen et al., (2011) Presence/absence, differential expression and sequence polymorphisms between PiAVR2 and PiAVR2-like in Phytophthora infestans determine virulence on R2 plants. New Phytologist, 191:763-776 DOI: 10.1111/j.1469-8137.2011.03736.x.

Patents: Solomon, P.S., Breen, S., Fleetwood, D., Ford, S. (2016) IP Australia, 2016. Patent Application Number 20169000251