Roq1 mediates recognition of the Xanthomonas and Pseudomonas effector proteins XopQ and HopQ1

Abstract

SUMMARYXanthomonas spp. are phytopathogenic bacteria that can cause disease on a wide variety of plant species resulting in significant impacts on crop yields. Limited genetic resistance is available in most crop species and current control methods are often inadequate, particularly when environmental conditions favor disease. The plant Nicotiana benthamiana has been shown to be resistant to Xanthomonas and Pseudomonas due to an immune response triggered by the bacterial effector proteins XopQ and HopQ1, respectively. We used a reverse genetic screen to identify Recognition of XopQ 1 (Roq1), a nucleotide-binding leucine-rich repeat (NLR) protein with a Toll-like interleukin-1 receptor (TIR) domain, which mediates XopQ recognition in N. benthamiana. Roq1 orthologs appear to be present only in the Nicotiana genus. Expression of Roq1 was found to be sufficient for XopQ recognition in both the closely-related Nicotiana sylvestris and the distantly-related beet plant (Beta vulgaris). Roq1 was found to co-immunoprecipitate with XopQ, suggesting a physical association between the two proteins. Roq1 is able to recognize XopQ alleles from various Xanthomonas species, as well as HopQ1 from Pseudomonas, demonstrating widespread potential application in protecting crop plants from these pathogens.

The Xanthomonas effector XopL uncovers the role of microtubules in stromule extension and dynamics in Nicotiana benthamiana

“…It is known that N . benthamiana recognizes XopQ, via the R protein Roq1 (Schultink et al, ), and initiates ETI responses (Schwartz et al ., ; Adlung et al ., ; Adlung and Bonas, ). Although the XopQ‐triggered stromule induction is impressive it is not surprising given the known link between ETI and increased stromule frequencies (Caplan et al ., ).…”

The type III effector RipB from Ralstonia solanacearum RS1000 acts as a major avirulence factor in Nicotiana benthamiana and other Nicotiana species

“…a). The close homologues of RipB, such as HopQ1 and XopQ, have been identified from Pseudomonas and Xanthomonas strains, respectively (Schultink et al , ). The three amino acids substituted in RipB BK were variable and not conserved among the eight RipB homologues from R. solanacearum , Pseudomonas and Xanthomonas strains (Fig.…”

“…Recently, Schultink et al () have reported that the N. benthamiana NLR protein Roq1 recognizes the Xanthomonas effector XopQ, which is a close homologue of RipB. The intact orthologue gene Roq1 is present in N. tabacum , but not in N. sylvestris .…”

“…Recent research revealed that the TIR‐NLR protein Roq1 recognizes XopQ and HopQ1 in N. benthamiana (Schultink et al , ). In this study, we observed that R. solanacearum RS1002 is avirulent in Nicotiana plants that contain an intact Roq1 , but not in N. sylvestris that contains an aberrant copy of Roq1 (Fig.…”

Defining essential processes in plant pathogenesis with Pseudomonas syringae pv. tomato DC3000 disarmed polymutants and a subset of key type III effectors

“…ETI processes have been extensively studied using Pst DC3000 derivatives, deploying AvrPto or AvrPtoB in tomato accessions expressing the Pto/Prf decoy/NLR proteins or deploying effectors such as AvrRpt2 that are from different P. syringae strains and confer NLR-dependent avirulence in appropriate Arabidopsis accessions (Cui et al, 2015;Jones et al, 2016;Khan et al, 2016;Martin, 2012). A cognate NLR has recently been identified for HopQ1 in N. benthamiana (Schultink et al, 2017), but none has been found in any plant for HopAD1, HopM1, AvrE1 or HopAM1. The plethora of T3Es in the DC3000 repertoire that show some capacity to elicit cell death in N. benthamiana suggests that ETI suppression may be an important function of native repertoires.…”