title: Genetic analysis of environmental strains of the plant pathogen Phytophthora capsici reveals heterogeneous repertoire of effectors and possible effector evolution via genomic island.
abstract: Phytophthora capsici is a virulent oomycete pathogen of many vegetable crops. Recently, it has been demonstrated that the recognition of the RXLR effector AVR3a1 of P. capsici (PcAVR3a1) triggers a hypersensitive response and plays a critical role in mediating non-host resistance. Here, we analyzed the occurrence of PcAVR3a1 in 57 isolates of P. capsici derived from globe squash, eggplant, tomato and bell pepper cocultivated in a small geographical area. The occurrence of PcAVR3a1 in environmental strains of P. capsici was confirmed by PCR in only 21 of these pathogen isolates. To understand the presence-absence pattern of PcAVR3a1 in environmental strains, the flanking region of this gene was sequenced. PcAVR3a1 was found within a genetic element that we named PcAVR3a1-GI (PcAVR3a1 genomic island). PcAVR3a1-GI was flanked by a 22-bp direct repeat, which is related to its site-specific recombination site. In addition to the PcAVR3a1 gene, PcAVR3a1-GI also encoded a phage integrase probably associated with the excision and integration of this mobile element. Exposure to plant induced the presence of an episomal circular intermediate of PcAVR3a1-GI, indicating that this mobile element is functional. Collectively, these findings provide evidence of PcAVR3a1 evolution via mobile elements in environmental strains of Phytophthora.
authors.affiliation: CONICET, Cuidad Autónoma de Buenos Aires, CP1661, Argentina Universidad Nacional de Luján, Buenos Aires, CP1428, Argentina.
authors.forename: María Josefina
authors.initials: MJ
authors.lastname: Iribarren
authors.affiliation: CONICET, Cuidad Autónoma de Buenos Aires, CP1661, Argentina Instituto de Genética Ewald A. Favret, Buenos Aires, CP1712, Argentina.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Pascuan
authors.affiliation: CONICET, Cuidad Autónoma de Buenos Aires, CP1661, Argentina Instituto de Genética Ewald A. Favret, Buenos Aires, CP1712, Argentina.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Soto
authors.affiliation: CONICET, Cuidad Autónoma de Buenos Aires, CP1661, Argentina Instituto de Genética Ewald A. Favret, Buenos Aires, CP1712, Argentina ayub.nicolas@inta.gob.ar.
authors.forename: Nicolás Daniel
authors.initials: ND
authors.lastname: Ayub
mesh_terms: D004783:Environmental Microbiology; D019143:Evolution, Molecular; D044404:Genomic Islands; D020071:Interspersed Repetitive Sequences; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000235:genetics* / Q000302:isolation & purification; D010957:Plasmids; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014675:Vegetables / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D037521:Virulence Factors
keywords: AVR3a1; Phytophthora capsici; RXLR effector; genomic island; integrase; vegetable crops