title: Systemic Responses of Barley to the 3-hydroxy-decanoyl-homoserine Lactone Producing Plant Beneficial EndophyteAcidovorax radicisN35.
abstract: Quorum sensing auto-inducers of theN-acyl homoserine lactone (AHL) type produced by Gram-negative bacteria have different effects on plants including stimulation on root growth and/or priming or acquirement of systemic resistance in plants. In this communication the influence of AHL production of the plant growth promoting endophytic rhizosphere bacteriumAcidovorax radicisN35 on barley seedlings was investigated.A. radicisN35 produces 3-hydroxy-C10-homoserine lactone (3-OH-C10-HSL) as the major AHL compound. To study the influence of this QS autoinducer on the interaction with barley, thearaI-biosynthesis gene was deleted. The comparison of inoculation effects of theA. radicisN35 wild type and thearaImutant resulted in remarkable differences. While the N35 wild type colonized plant roots effectively in microcolonies, thearaImutant occurred at the root surface as single cells. Furthermore, in a mixed inoculum the wild type was much more prevalent in colonization than thearaImutant documenting that thearaImutation affected root colonization. Nevertheless, a significant plant growth promoting effect could be shown after inoculation of barley with the wild type and thearaImutant in soil after 2 months cultivation. WhileA. radicisN35 wild type showed only a very weak induction of early defense responses in plant RNA expression analysis, thearaImutant caused increased expression of flavonoid biosynthesis genes. This was corroborated by the accumulation of several flavonoid compounds such as saponarin and lutonarin in leaves of root inoculated barley seedlings. Thus, although the exact role of the flavonoids in this plant response is not clear yet, it can be concluded, that the synthesis of AHLs byA. radicishas implications on the perception by the host plant barley and thereby contributes to the establishment and function of the bacteria-plant interaction.
authors.affiliation: Research Unit Microbe-Plant Interactions, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Shengcai
authors.initials: S
authors.lastname: Han
authors.affiliation: Research Unit Microbe-Plant Interactions, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Research Unit Plant Genome and Systems Biology, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Trost
authors.affiliation: Research Unit Plant Genome and Systems Biology, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Klaus F
authors.initials: KF
authors.lastname: Mayer
authors.affiliation: Department Environmental Sciences, Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: A Corina
authors.initials: AC
authors.lastname: Vlot
authors.affiliation: Department Environmental Sciences, Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Heller
authors.affiliation: Research Unit Microbe-Plant Interactions, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.affiliation: Research Unit Microbe-Plant Interactions, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Anton
authors.initials: A
authors.lastname: Hartmann
authors.affiliation: Research Unit Microbe-Plant Interactions, Department Environmental Sciences, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) Neuherberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Rothballer
keywords: 3-OH-C10-homoserine lactone; Acidovorax radicis; endophytes; flavonoids; plant growth promoting bacteria (PGPB); systemic plant responses