Abstract: Rust diseases significantly threaten cereals and other crops, causing substantial losses in crop production worldwide and endangering global food security. Rust fungi produce molecular weapons called disease effectors to overcome host resistance. Host plants have evolved receptors (resistance proteins) able to recognise some of these effectors (avirulence proteins) and trigger disease resistance. The interaction between flax and the flax rust fungus, Melampsora lini, is a model pathosystem helping us to understand the molecular basis of rust fungal pathogenicity in plants. M. lini deploys an inhibitor gene (I-1) that interacts with avirulence (Avr) genes to prevent a resistance response triggered by corresponding flax resistance (R) genes. My PhD project was designed to identify and functionally characterise the M. lini Inhibitor gene to fill the gap in our understanding of how it promotes disease development by interfering with host-pathogen interactions. To investigate its function, I-1 was tested against some other genetically inhibited and noninhibited M. lini Avr genes to determine its range of inhibition. For example, the inhibitable AvrL1 and AvrL8 genes were cloned and studied along with I-1. I-1 was also tested for inhibition of selected autoreactive inducers of plant cell death, including the TIR- and CC-domains of various plant disease-resistance proteins. While the inhibitor genes inhibited the recognition of some Avr genes, no inhibition was found against other cell death inducers. Inhibition function was found to extend to TIR-domain-induced signalling and suppression of ROS (reactive oxygen species) production. I-1 was found to show cytosolic and nuclear localisation in planta whereas AvrL1 showed peroxisomal localisation and AvrL8 was targeted to the cytosol. AvrL1 and AvrL8 both caused suppression of ROS production when expressedinside Nicotiana benthamiana leaves. These results suggest that the inhibitor acts downstream of effector recognition.

Biography: My Bachelor of Science degree was in Agricultural Sciences, and my Master of Science was in Plant Pathology from Bangabandhu Agricultural University (BSMRAU, renaming under process to ‘Gazipur Agricultural University’). I started my career as a Lecturer of Plant Pathology at BSMRAU in 2013. I was then promoted to Assistant Professor of the same department and worked on tomato viruses (Master of Science Thesis), identification of plant-pathogenic fungi, plant disease resistance, and fungicide resistance. I joined David Jones’s Lab in RSB in 2019 to work on the Identification and functional characterisation of rust-fungi inhibitor(s). I look forward to returning to my home university and resuming my career.