Natural variation in the Arabidopsis AGO2 gene alters antiviral activity
P. MOFFETT (1), A. Adurogbangba (1), C. Roussin-Léveillé (1), C. Brosseau (1) (1) Université de Sherbrooke, Canada

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. 

Abstract Number: C8-6, P12-407
Session Type: Concurrent