Use of Arabidopsis recombinant inbred lines reveals a monogenic and a novel digenic resistance mechanism to Xanthomonas campestris pv campestris

Abstract

SummaryInfiltration of the Arabidopsis thaliana accession Landsberg erecta (Ler) with Xanthomonas campestris pv campestris isolate 2D520 results in extensive necrosis and limited chlorosis within 5-6 days post-inoculation (d.p.i.}, which can lead to systemic necrosis within 23 d.p.i. In contrast, the accession Columbia (Col) remains asymptomatic after infiltration. Although both accessions support bacterial growth, 5-28-fold more bacteria are present in Let than in Col leaf tissue. Inheritance studies indicate that three independent, dominant or partially dominant, nuclear genes condition resistance to X. c. campestris 2D520. The major gene, termed RXC2, conditions monogenic resistance to X. c. campestris and was mapped to a 5.5 cM interval of chromosome V. Segregation data indicate that the locus RXC3 in conjunction with RXC4 confers digenic resistance to X. c. campestris. The combined action of RXC3 and RXC4 is correlated with a suppression of in planta bacterial levels and a suppression of symptoms relative to Ler. The RXC3 + RXC4-mediated resistance is novel in that although the Col allele of RXC4 contributes positively to resistance, it is the Ler and not the Col allele of RXC3 that contributes positively to resistance. RXC3 was mapped to the bottom arm of chromosome V in a 2.7 cM interval within the major recognition gene complex MRC-J, a cluster of genes involved in disease resistance. RXC4 was mapped to a 12 cM interval on chromosome II that also contains RXCl, a gene conferring tolerance to X. c. campestris.

The Xanthomonas Type III Effector XopD Targets the Arabidopsis Transcription Factor MYB30 to Suppress Plant Defense

“…By contrast, significantly different bacterial growth rates were detected after inoculation with these two strains using 10 7 cfu/mL, suggesting that a certain XopD dose may be required to detect XopD contribution to promotion of bacterial growth in Col-0 plants ( Figure 4D). It is important to note that, in contrast with the more widely reported Arabidopsis inoculation assays with Pseudomonas syringae, inoculations with X. campestris using bacterial densities of 10 7 (and even 10 8 ) cfu/mL are frequently reported in the literature (Buell and Somerville, 1997). Consistent with the observed dose-dependent XopD-mediated effects, Col-0 plants inoculated with XccB100DxopD (+XopD XccB100 ) were more susceptible than those inoculated with XccB100 (+GUS) using 5 3 10 5 cfu/mL ( Figure 4C).…”

Within-Species Flagellin Polymorphism inXanthomonas campestrispvcampestrisand Its Impact on Elicitation ofArabidopsis FLAGELLIN SENSING2–Dependent Defenses

“…We observed faint chlorosis after 3 d in the plants inoculated with Xcc B18, B186, and 2669 (strains that produced noneliciting extracts; Figure 1). The severity of chlorosis increased over time, producing symptoms typical of virulent Xcc infiltrated into Arabidopsis leaf mesophyll ( Figure 6A) (Simpson and Johnson, 1990;Parker et al, 1993;Buell and Somerville, 1997). By contrast, no disease symptoms were visible in Col-0 plants inoculated with the eliciting Xcc strains B127 and B305, even after 2 weeks.…”

“…In the xylem, Xcc growth causes darkening of the veins and eventual death of the infected tissue. Many aspects of Arabidopsis-Xcc interactions have been studied (Bent et al, 1992;Lummerzheim et al, 1993;Parker et al, 1993;Buell and Somerville, 1997;Hugouvieux et al, 1998;Godard et al, 2000;Korves and Bergelson, 2003;O'Donnell et al, 2003;Silipo et al, 2005). The extensive progress made by Boller and colleagues concerning Arabidopsis FLS2-mediated flagellin detection Zipfel et al, 2004) motivated our examination of Arabidopsis-Xcc interactions with respect to flagellin detection.…”

Bay-0 × Shahdara recombinant inbred line population: a powerful tool for the genetic dissection of complex traits in Arabidopsis

“…The extensive natural variation that occurs in Arabidopsis is being increasingly exploited as a source of genetic variability for the analysis of important agronomic traits (review in Alonso-Blanco and Koornneef 2000). Indeed, genes involved for example in disease resistance, or more recently in flowering time, have been cloned (Buell and Somerville 1997;Michaels and Amasino 1999;Johanson et al 2000), allowing investigation of the molecular basis of the allelic variation. The first step required for the successful cloning of genes associated with major QTLs is the generation of suitable mapping populations.…”