title: Silencing of Vlaro2 for chorismate synthase revealed that the phytopathogen Verticillium longisporum induces the cross-pathway control in the xylem.
abstract: The first leaky auxotrophic mutant for aromatic amino acids of the near-diploid fungal plant pathogen Verticillium longisporum (VL) has been generated. VL enters its host Brassica napus through the roots and colonizes the xylem vessels. The xylem contains little nutrients including low concentrations of amino acids. We isolated the gene Vlaro2 encoding chorismate synthase by complementation of the corresponding yeast mutant strain. Chorismate synthase produces the first branch point intermediate of aromatic amino acid biosynthesis. A novel RNA-mediated gene silencing method reduced gene expression of both isogenes by 80% and resulted in a bradytrophic mutant, which is a leaky auxotroph due to impaired expression of chorismate synthase. In contrast to the wild type, silencing resulted in increased expression of the cross-pathway regulatory gene VlcpcA (similar to cpcA/GCN4) during saprotrophic life. The mutant fungus is still able to infect the host plant B. napus and the model Arabidopsis thaliana with reduced efficiency. VlcpcA expression is increased in planta in the mutant and the wild-type fungus. We assume that xylem colonization requires induction of the cross-pathway control, presumably because the fungus has to overcome imbalanced amino acid supply in the xylem.
authors.affiliation: Institut für Mikrobiologie und Genetik, Georg-August-Universität, Grisebachstr. 8, 37077 Göttingen, Germany.
authors.forename: Seema
authors.initials: S
authors.lastname: Singh
authors.forename: Susanna A
authors.initials: SA
authors.lastname: Braus-Stromeyer
authors.forename: Christian
authors.initials: C
authors.lastname: Timpner
authors.forename: Van Tuan
authors.initials: VT
authors.lastname: Tran
authors.forename: Gertrud
authors.initials: G
authors.lastname: Lohaus
authors.forename: Michael
authors.initials: M
authors.lastname: Reusche
authors.forename: Jessica
authors.initials: J
authors.lastname: Knüfer
authors.forename: Thomas
authors.initials: T
authors.lastname: Teichmann
authors.forename: Andreas
authors.initials: A
authors.lastname: von Tiedemann
authors.forename: Gerhard H
authors.initials: GH
authors.lastname: Braus
mesh_terms: D017360:Arabidopsis; D029688:Brassica napus / Q000378:metabolism* / Q000382:microbiology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D020172:Verticillium / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D052584:Xylem / Q000378:metabolism* / Q000382:microbiology
chemical_list: D005656:Fungal Proteins; C019895:chorismate synthase; D019761:Phosphorus-Oxygen Lyases