title: A Recent Expansion of the RXLR Effector Gene Avrblb2 Is Maintained in Global Populations of Phytophthora infestans Indicating Different Contributions to Virulence.
abstract: The introgression of disease resistance (R) genes encoding immunoreceptors with broad-spectrum recognition into cultivated potato appears to be the most promising approach to achieve sustainable management of late blight caused by the oomycete pathogen Phytophthora infestans. Rpi-blb2 from Solanum bulbocastanum shows great potential for use in agriculture based on preliminary potato disease trials. Rpi-blb2 confers immunity by recognizing the P. infestans avirulence effector protein AVRblb2 after it is translocated inside the plant cell. This effector belongs to the RXLR class of effectors and is under strong positive selection. Structure-function analyses revealed a key polymorphic amino acid (position 69) in AVRblb2 effector that is critical for activation of Rpi-blb2. In this study, we reconstructed the evolutionary history of the Avrblb2 gene family and further characterized its genetic structure in worldwide populations. Our data indicate that Avrblb2 evolved as a single-copy gene in a putative ancestral species of P. infestans and has recently expanded in the Phytophthora spp. that infect solanaceous hosts. As a consequence, at least four variants of AVRblb2 arose in P. infestans. One of these variants, with a Phe residue at position 69, evades recognition by the cognate resistance gene. Surprisingly, all Avrblb2 variants are maintained in pathogen populations. This suggests a potential benefit for the pathogen in preserving duplicated versions of AVRblb2, possibly because the variants may have different contributions to pathogen fitness in a diversified solanaceous host environment.
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Ricardo F
authors.initials: RF
authors.lastname: Oliva
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Liliana M
authors.initials: LM
authors.lastname: Cano
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Sylvain
authors.initials: S
authors.lastname: Raffaele
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Joe
authors.initials: J
authors.lastname: Win
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Tolga O
authors.initials: TO
authors.lastname: Bozkurt
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Khaoula
authors.initials: K
authors.lastname: Belhaj
authors.affiliation: 2 Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea;
authors.forename: Sang-Keun
authors.initials: SK
authors.lastname: Oh
authors.affiliation: 3 Biodiversity and Climate Research Centre BiK-F, Senckenberganlage 25, D-60325 Frankfurt (Main), Germany;|4 Goethe University, Department of Biological Sciences, Institute of Ecology, Evolution and Diversity, Siesmayer. 70, D-60323 Frankfurt (Main), Germany;|5 Senckenberg Gesellschft für Naturforschung, Senckenbergallee 25, D-60325 Frankfurt (Main), Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Thines
authors.affiliation: 1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
authors.forename: Sophien
authors.initials: S
authors.lastname: Kamoun
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D014644:Genetic Variation; D054884:Host-Pathogen Interactions / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D010838:Phytophthora / Q000235:genetics; D055750:Phytophthora infestans / Q000235:genetics* / Q000472:pathogenicity*; D011110:Polymorphism, Genetic; D011198:Solanum tuberosum / Q000235:genetics / Q000382:microbiology; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D037521:Virulence Factors