title: A Galpha subunit controls zoospore motility and virulence in the potato late blight pathogen Phytophthora infestans.
abstract: The heterotrimeric G-protein pathway is a ubiquitous eukaryotic signalling module that is known to regulate growth and differentiation in many plant pathogens. We previously identified Pigpa1, a gene encoding a G-protein alpha subunit from the potato late blight pathogen Phytophthora infestans. P. infestans belongs to the class oomycetes, a group of organisms in which signal transduction processes have not yet been studied at the molecular level. To elucidate the function of Pigpa1, PiGPA1-deficient mutants were obtained by homology-dependent gene silencing. The Pigpa1-silenced mutants produced zoospores that turned six to eight times more frequently, causing them to swim only short distances compared with wild type. Attraction to the surface, a phenomenon known as negative geotaxis, was impaired in the mutant zoospores, as well as autoaggregation and chemotaxis towards glutamic and aspartic acid. Zoospore production was reduced by 20-45% in different Pigpa1-silenced mutants. Transformants expressing constitutively active forms of PiGPA1, containing amino acid substitutions (R177H and Q203L), showed no obvious phenotypic differences from the wild-type strain. Infection efficiencies on potato leaves ranged from 3% to 14% in the Pigpa1-silenced mutants, compared with 77% in wild type, showing that virulence is severely impaired. The results prove that PiGPA1 is crucial for zoospore motility and for pathogenicity in an important oomycete plant pathogen.
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Binnenhaven, The Netherlands.
authors.forename: Maita
authors.initials: M
authors.lastname: Latijnhouwers
authors.forename: Wilco
authors.initials: W
authors.lastname: Ligterink
authors.forename: Vivianne G A A
authors.initials: VG
authors.lastname: Vleeshouwers
authors.forename: Pieter
authors.initials: P
authors.lastname: van West
authors.forename: Francine
authors.initials: F
authors.lastname: Govers
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000502:physiology; D002449:Cell Aggregation / Q000235:genetics / Q000502:physiology; D002633:Chemotaxis / Q000235:genetics / Q000502:physiology; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics* / Q000502:physiology*; D015870:Gene Expression; D020868:Gene Silencing; D009068:Movement; D009154:Mutation; D010838:Phytophthora / Q000235:genetics / Q000472:pathogenicity*; D010935:Plant Diseases / Q000382:microbiology*; D015398:Signal Transduction / Q000502:physiology; D011198:Solanum tuberosum / Q000382:microbiology; D013170:Spores / Q000235:genetics / Q000502:physiology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics* / Q000502:physiology
chemical_list: D020418:Algal Proteins; D044385:GTP-Binding Protein alpha Subunits; D037521:Virulence Factors