Biotic Stress/Applied Plant Bio

Abstract

CS-23-1 - Natural variation in the Arabidopsis AGO2 gene alters antiviral activity

Tuesday, July 17
8:33 AM - 8:53 AM

RNA silencing functions as an anti-viral defence through the action of DICER-like (DCL) and ARGONAUTE (AGO) proteins. We have previously shown that Potato virus X (PVX) is unable to infect Arabidopsis thaliana due in part to the AGO2 protein. We have used transient expression to investigate why PVX is able to infect Nicotiana benthamiana despite the latter having a functional AGO2 protein. We find that AtAGO2 inhibits PVX whereas NbAGO2 does not. Consistent with this, the stability of NbAGO2 is compromised by the PVX viral suppressor of RNA silencing, P25, whereas AtAGO2 is not. These results suggest that AGO2 plays a role in virus host range determination. To better understand how variability in AGO2 might influence antiviral activity, we compared the AGO2 sequences of several hundred Arabidopsis ecotypes and investigated the susceptibility of over forty ecotypes to PVX. We found a very high level of non-synonymous mutations in the AGO2 gene between different ecotypes compared to AGO1, suggesting that this gene has undergone positive selection at one codon in particular. Infection assays indicate that susceptibility to PVX is determined by this same polymorphic codon, with approximately half of the tested ecotypes being susceptible to PVX. This polymorphism however did not affect resistance to bacteria or AGO2-dependent DNA methylation. Our results indicate that natural variation in RNA silencing components may be an important aspect in determining virus susceptibility.


 

Co-Authors

Ayooluwa Adurogbangba – Université de Sherbrooke; Charles Roussin-Léveillée – Université de Sherbrooke; Zhenxing Zhao – Université de Sherbrooke; Chantal Brosseau – Université de Sherbrooke

Peter Moffett, PhD

Professor
Université de Sherbrooke

Our research is aimed at understanding the plant innate immune system, with the long-term goal of applying this knowledge to the generation of disease resistant plants. Our research uses several model systems, including tobacco, potato and Arabidopsis to study plant-virus and plant-viroidinteractions in particular, and plant-pathogen interactions in general. This includes the study of how plants recognize pathogens, the signaling molecules involved in disease resistance and ultimately, how plants eliminate pathogens.

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