title: LOV-domain photoreceptor, encoded in a genomic island, attenuates the virulence of Pseudomonas syringae in light-exposed Arabidopsis leaves.
abstract: In Arabidopsis thaliana, light signals modulate the defences against bacteria. Here we show that light perceived by the LOV domain-regulated two-component system (Pst-Lov) of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) modulates virulence against A. thaliana. Bioinformatic analysis and the existence of an episomal circular intermediate indicate that the locus encoding Pst-Lov is present in an active genomic island acquired by horizontal transfer. Strains mutated at Pst-Lov showed enhanced growth on minimal medium and in leaves of A. thaliana exposed to light, but not in leaves incubated in darkness or buried in the soil. Pst-Lov repressed the expression of principal and alternative sigma factor genes and their downstream targets linked to bacterial growth, virulence and quorum sensing, in a strictly light-dependent manner. We propose that the function of Pst-Lov is to distinguish between soil (dark) and leaf (light) environments, attenuating the damage caused to host tissues while releasing growth out of the host. Therefore, in addition to its direct actions via photosynthesis and plant sensory receptors, light may affect plants indirectly via the sensory receptors of bacterial pathogens.
authors.affiliation: IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas, Avenida San Martín 4453, Buenos Aires, 1417, Argentina; Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, C1405BWE, Argentina.
authors.forename: Victoria
authors.initials: V
authors.lastname: Moriconi
authors.forename: Romina
authors.initials: R
authors.lastname: Sellaro
authors.forename: Nicolás
authors.initials: N
authors.lastname: Ayub
authors.forename: Gabriela
authors.initials: G
authors.lastname: Soto
authors.forename: Matías
authors.initials: M
authors.lastname: Rugnone
authors.forename: Rashmi
authors.initials: R
authors.lastname: Shah
authors.forename: Gopal P
authors.initials: GP
authors.lastname: Pathak
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gärtner
authors.forename: Jorge J
authors.initials: JJ
authors.lastname: Casal
mesh_terms: D017360:Arabidopsis / Q000382:microbiology / Q000528:radiation effects; D015964:Gene Expression Regulation, Bacterial; D022761:Gene Transfer, Horizontal; D044404:Genomic Islands; D008027:Light; D016366:Open Reading Frames; D009876:Operon; D020283:Photoreceptors, Microbial / Q000235:genetics* / Q000528:radiation effects; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology* / Q000528:radiation effects; D044224:Pseudomonas syringae / Q000235:genetics / Q000472:pathogenicity*; D053038:Quorum Sensing; D012808:Sigma Factor / Q000378:metabolism; D014774:Virulence
chemical_list: D020283:Photoreceptors, Microbial; D012808:Sigma Factor
keywords: Arabidopsis thaliana; LOV domain; Pseudomonas syringae pv. tomato DC3000; light; plant-pathogen interaction; two-component system