title: Imbalanced lignin biosynthesis promotes the sexual reproduction of homothallic oomycete pathogens.
abstract: Lignin is incorporated into plant cell walls to maintain plant architecture and to ensure long-distance water transport. Lignin composition affects the industrial value of plant material for forage, wood and paper production, and biofuel technologies. Industrial demands have resulted in an increase in the use of genetic engineering to modify lignified plant cell wall composition. However, the interaction of the resulting plants with the environment must be analyzed carefully to ensure that there are no undesirable side effects of lignin modification. We show here that Arabidopsis thaliana mutants with impaired 5-hydroxyguaiacyl O-methyltransferase (known as caffeate O-methyltransferase; COMT) function were more susceptible to various bacterial and fungal pathogens. Unexpectedly, asexual sporulation of the downy mildew pathogen, Hyaloperonospora arabidopsidis, was impaired on these mutants. Enhanced resistance to downy mildew was not correlated with increased plant defense responses in comt1 mutants but coincided with a higher frequency of oomycete sexual reproduction within mutant tissues. Comt1 mutants but not wild-type Arabidopsis accumulated soluble 2-O-5-hydroxyferuloyl-L-malate. The compound weakened mycelium vigor and promoted sexual oomycete reproduction when applied to a homothallic oomycete in vitro. These findings suggested that the accumulation of 2-O-5-hydroxyferuloyl-L-malate accounted for the observed comt1 mutant phenotypes during the interaction with H. arabidopsidis. Taken together, our study shows that an artificial downregulation of COMT can drastically alter the interaction of a plant with the biotic environment.
authors.affiliation: Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France.
authors.forename: Michaël
authors.initials: M
authors.lastname: Quentin
authors.forename: Valérie
authors.initials: V
authors.lastname: Allasia
authors.forename: Anthony
authors.initials: A
authors.lastname: Pegard
authors.forename: Florent
authors.initials: F
authors.lastname: Allais
authors.forename: Paul-Henri
authors.initials: PH
authors.lastname: Ducrot
authors.forename: Bruno
authors.initials: B
authors.lastname: Favery
authors.forename: Caroline
authors.initials: C
authors.lastname: Levis
authors.forename: Sophie
authors.initials: S
authors.lastname: Martinet
authors.forename: Clarissa
authors.initials: C
authors.lastname: Masur
authors.forename: Michel
authors.initials: M
authors.lastname: Ponchet
authors.forename: Dominique
authors.initials: D
authors.lastname: Roby
authors.forename: Nikolaus L
authors.initials: NL
authors.lastname: Schlaich
authors.forename: Lise
authors.initials: L
authors.lastname: Jouanin
authors.forename: Harald
authors.initials: H
authors.lastname: Keller
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D008031:Lignin / Q000096:biosynthesis*; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism; D009868:Oomycetes / Q000472:pathogenicity* / Q000502:physiology; D010935:Plant Diseases / Q000235:genetics; D012098:Reproduction
chemical_list: D008031:Lignin; D008780:Methyltransferases; C019608:caffeate O-methyltransferase