title: Two independent S-phase checkpoints regulate appressorium-mediated plant infection by the rice blast fungus Magnaporthe oryzae.
abstract: To cause rice blast disease, the fungal pathogen Magnaporthe oryzae develops a specialized infection structure called an appressorium. This dome-shaped, melanin-pigmented cell generates enormous turgor and applies physical force to rupture the rice leaf cuticle using a rigid penetration peg. Appressorium-mediated infection requires septin-dependent reorientation of the F-actin cytoskeleton at the base of the infection cell, which organizes polarity determinants necessary for plant cell invasion. Here, we show that plant infection by M. oryzae requires two independent S-phase cell-cycle checkpoints. Initial formation of appressoria on the rice leaf surface requires an S-phase checkpoint that acts through the DNA damage response (DDR) pathway, involving the Cds1 kinase. By contrast, appressorium repolarization involves a novel, DDR-independent S-phase checkpoint, triggered by appressorium turgor generation and melanization. This second checkpoint specifically regulates septin-dependent, NADPH oxidase-regulated F-actin dynamics to organize the appressorium pore and facilitate entry of the fungus into host tissue.
authors.affiliation: School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
authors.forename: Míriam
authors.initials: M
authors.lastname: Osés-Ruiz
authors.affiliation: School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
authors.forename: Wasin
authors.initials: W
authors.lastname: Sakulkoo
authors.affiliation: School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
authors.forename: George R
authors.initials: GR
authors.lastname: Littlejohn
authors.affiliation: School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Martin-Urdiroz
authors.affiliation: School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom N.J.Talbot@exeter.ac.uk.
authors.forename: Nicholas J
authors.identifier: 0000-0001-6434-7757
authors.initials: NJ
authors.lastname: Talbot
mesh_terms: D004249:DNA Damage; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D020082:Magnaporthe / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D012275:Oryza / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D059807:S Phase Cell Cycle Checkpoints
chemical_list: D005656:Fungal Proteins
keywords: Pyricularia; appressorium; cell cycle; fungi; pathogen