title: Physcomitrella patens auxin conjugate synthetase (GH3) double knockout mutants are more resistant to Pythium infection than wild type.
abstract: Auxin homeostasis is involved in many different plant developmental and stress responses. The auxin amino acid conjugate synthetases belonging to the GH3 family play major roles in the regulation of free indole-3-acetic acid (IAA) levels and the moss Physcomitrella patens has two GH3 genes in its genome. A role for IAA in several angiosperm--pathogen interactions was reported, however, in a moss--oomycete pathosystem it had not been published so far. Using GH3 double knockout lines we have investigated the role of auxin homeostasis during the infection of P. patens with the two oomycete species, Pythium debaryanum and Pythium irregulare. We show that infection with P. debaryanum caused stronger disease symptoms than with P. irregulare. Also, P. patens lines harboring fusion constructs of an auxin-inducible promoter from soybean (GmGH3) with a reporter (ß-glucuronidase) showed higher promoter induction after P. debaryanum infection than after P. irregulare, indicating a differential induction of the auxin response. Free IAA was induced upon P. debaryanum infection in wild type by 1.6-fold and in two GH3 double knockout (GH3-doKO) mutants by 4- to 5-fold. All GH3-doKO lines showed a reduced disease symptom progression compared to wild type. Since P. debaryanum can be inhibited in growth on medium containing IAA, these data might indicate that endogenous high auxin levels in P. patens GH3-doKO mutants lead to higher resistance against the oomycete.
authors.affiliation: Institut für Botanik, Technische Universität Dresden, D-01062 Dresden, Germany. Electronic address: Jennifer.Mittag@web.de.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mittag
authors.affiliation: Department of Biology, University of Zagreb, 10000 Zagreb, Croatia. Electronic address: ivana.sola@biol.pmf.hr.
authors.forename: Ivana
authors.initials: I
authors.lastname: Šola
authors.affiliation: Department of Biology, University of Zagreb, 10000 Zagreb, Croatia. Electronic address: gordana.rusak@biol.pmf.hr.
authors.forename: Gordana
authors.initials: G
authors.lastname: Rusak
authors.affiliation: Institut für Botanik, Technische Universität Dresden, D-01062 Dresden, Germany. Electronic address: Jutta.Ludwig-Mueller@tu-dresden.de.
authors.forename: Jutta
authors.initials: J
authors.lastname: Ludwig-Müller
mesh_terms: D019068:Bryopsida / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011775:Pythium / Q000502:physiology*; D030262:Soybean Proteins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity
chemical_list: C070797:GH3 protein, soybean; D007210:Indoleacetic Acids; D030262:Soybean Proteins; C030737:indoleacetic acid; D005966:Glucuronidase
keywords: Auxin homeostasis; Indole-3-acetic acid; Non-vascular plant; Oomycete