New, ground-breaking stem rust research is highlighted in the prestigious journal Science published on Dec 22 2017. A perspective entitled “The Quest for Durable Resistance” by Matthew J. Moscou and Peter van Esse provides context and outlines the significance of two research papers that independently identify two Avr effectors from the fungal pathogen Puccinia graminis f.sp. tritici, the causal agent of wheat stem rust. These research papers are considered a milestone in terms of improving our understanding the biology of rust pathogens.
In the first research paper entitled “Variation in the AvrSr35 gene determines Sr35 resistance against wheat stem rust race Ug99”, Andres Salcedo and colleagues identify a fungal gene named AvrSr35 that is required for Sr35 avirulence. The effector protein encoded by this gene binds to the Sr35 resistance protein and as a result activates the plant’s immune response. In the second paper entitled “Loss of AvrSr50 by somatic exchange in stem rust leads to virulence for Sr50 resistance in wheat”, Jiapeng Chen and colleagues identify the gene AvrSr50 that is required for Sr50 avirulence. Similarly this effector protein interacts directly with the Sr50 protein, triggering Sr50-dependant defense responses. In the case of both identified Avr effectors, removal or inactivation renders the plant susceptible to fungal attack.
The results reported in these two papers represent a significant step forward in terms of getting a much better understanding of how plants interact with the rust pathogen.
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