title: Strigolactones as an auxiliary hormonal defence mechanism against leafy gall syndrome in Arabidopsis thaliana.
abstract: Leafy gall syndrome is the consequence of modified plant development in response to a mixture of cytokinins secreted by the biotrophic actinomycete Rhodococcus fascians. The similarity of the induced symptoms with the phenotype of plant mutants defective in strigolactone biosynthesis and signalling prompted an evaluation of the involvement of strigolactones in this pathology. All tested strigolactone-related Arabidopsis thaliana mutants were hypersensitive to R. fascians. Moreover, treatment with the synthetic strigolactone mixture GR24 and with the carotenoid cleavage dioxygenase inhibitor D2 illustrated that strigolactones acted as antagonistic compounds that restricted the morphogenic activity of R. fascians. Transcript profiling of the MORE AXILLARY GROWTH1 (MAX1), MAX2, MAX3, MAX4, and BRANCHED1 (BRC1) genes in the wild-type Columbia-0 accession and in different mutant backgrounds revealed that upregulation of strigolactone biosynthesis genes was triggered indirectly by the bacterial cytokinins via host-derived auxin and led to the activation of BRC1 expression, inhibiting the outgrowth of the newly developing shoots, a typical hallmark of leafy gall syndrome. Taken together, these data support the emerging insight that balances are critical for optimal leafy gall development: the long-lasting biotrophic interaction is possible only because the host activates a set of countermeasures-including the strigolactone response-in reaction to bacterial cytokinins to constrain the activity of R. fascians.
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium Department of Medical Protein Research, VIB, 9000 Gent, Belgium Department of Biochemistry, Ghent University, 9000 Gent, Belgium.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Stes
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium Ghent University Global Campus, Incheon 406-840, Republic of Korea.
authors.forename: Stephen
authors.initials: S
authors.lastname: Depuydt
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Annick
authors.initials: A
authors.lastname: De Keyser
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Cedrick
authors.initials: C
authors.lastname: Matthys
authors.affiliation: Department of Applied Biosciences, Ghent University, 9000 Gent, Belgium.
authors.forename: Kris
authors.initials: K
authors.lastname: Audenaert
authors.affiliation: Center for Bioscience Research & Education, Utsunomiya University, Utsunomiya 321-8505, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yoneyama
authors.affiliation: Department of Applied Biosciences, Ghent University, 9000 Gent, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: Werbrouck
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Goormachtig
authors.affiliation: Department of Applied Biosciences, Ghent University, 9000 Gent, Belgium danny.vereecke@ugent.be.
authors.forename: Danny
authors.initials: D
authors.lastname: Vereecke
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D007783:Lactones / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D012240:Rhodococcus / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D007783:Lactones; D010937:Plant Growth Regulators
keywords: Apical dominance; Gram-positive phytopathogen; witches’ broom.