Multiple Resistance Traits ControlPlum pox virusInfection inArabidopsis thaliana

Abstract

Twelve Arabidopsis accessions were challenged with Plum pox potyvirus (PPV) isolates representative of the four PPV strains. Each accession supported local and systemic infection by at least some of the PPV isolates, but high variability was observed in the behavior of the five PPV isolates or the 12 Arabidopsis accessions. Resistance to local infection or long-distance movement occurred in about 40% of all the accession-isolate combinations analyzed. Except for Nd-1, all accessions showed resistance to local infection by PPV-SoC; in the Landsberg erecta (Ler) accession, this resistance was compromised by sgt1 and rar1 mutations, suggesting that it could be controlled by an R gene-mediated resistance pathway. While most of the susceptible accessions were symptomless, PPV induced severe symptoms on inflorescences in C24, Ler, and Bay-0 as early as 15 days after inoculation. Genetic analyses indicated that these interaction phenotypes are controlled by different genetic systems. The restriction of long-distance movement of PPV-El Amar and of another member of genus Potyvirus, Lettuce mosaic virus, in Col-0 requires the RTM genes, indicating for the first time that the RTM system may provide a broad range, potyvirus-specific protection against systemic infection. The restriction to PPV-PS long-distance movement in Cvi-1 is controlled by a single recessive gene, designated rpv1, which was mapped to chromosome 1. The nuclear inclusion polymerase b-capsid protein region of the viral genome appears to be responsible for the ability of PPV-R to overcome rpv1-mediated resistance.

Identification of Quantitative Trait Loci Controlling Symptom Development During Viral Infection inArabidopsis thaliana

“…In all other experiments performed, a similar fraction of the inoculated Cvi plants were found to fail to accumulate the virus (discussed below). This observation was in contrast with our previous data (Decroocq et al 2006), in which we reported Cvi to be a susceptible, symptomless host of PPV-R. This discrepancy may be explained by the fact that the noninfected plants observed by Decroocq and associates (2006) were considered as inoculation escapes and were therefore discarded from further analyses.…”

“…One of them is mapping in the same region as the previously mapped resistance gene rpv1 (Decroocq et al 2006). rpv1 is controlling the resistance to PPV-PS infection, and we hypothesize that it is also partially controlling infection by PPV-R.…”

“…The nature of this resistance is still unknown. Since initially PPV-R was detected in inoculated Cvi leaves (Decroocq et al 2006), we hypothesized that this partial resistance was related to an inhibition of PPV long-distance movement. However, in a rpv1/rpv3 background, the mechanism leading to the digenic resistance has not yet been described.…”

“…Recently, we have shown that PPV, the causal agent of sharka disease in stone fruit trees, is able to infect A. thaliana (Decroocq et al 2006). A wide range of interaction outcomes were observed, depending on the host genotype or on the particular PPV isolate being used: resistance at the inoculation point (with no local virus multiplication detectable), resistance to systemic viral invasion (with viral accumulation in the inoculated leaves but not distantly from the inoculation point), and full systemic susceptibility.…”

“…Depending on the particular combination between a susceptible Arabidopsis accession and the viral isolate, a broad range of reactions were observed, from the absence of symptoms to severe symptom development. Initial efforts toward the identification of one or more genetic factors underlying this variability in symptom development indicated that, when confronted by the PPV-R (Rankovic) isolate, the difference in response between the Col-0 (Columbia) accession (mild symptoms) and the Ler (Landsberg erecta) accession (severe symptoms) is controlled by at least two loci and segregates as a quantitative trait (Decroocq et al 2006).…”