title: Silencing of the chalcone synthase gene in Casuarina glauca highlights the important role of flavonoids during nodulation.
abstract: Nitrogen-fixing root nodulation is confined to four plant orders, including > 14,000 Leguminosae, one nonlegume genus Parasponia and c. 200 actinorhizal species that form symbioses with rhizobia and Frankia bacterial species, respectively. Flavonoids have been identified as plant signals and developmental regulators for nodulation in legumes and have long been hypothesized to play a critical role during actinorhizal nodulation. However, direct evidence of their involvement in actinorhizal symbiosis is lacking. Here, we used RNA interference to silence chalcone synthase, which is involved in the first committed step of the flavonoid biosynthetic pathway, in the actinorhizal tropical tree Casuarina glauca. Transformed flavonoid-deficient hairy roots were generated and used to study flavonoid accumulation and further nodulation. Knockdown of chalcone synthase expression reduced the level of specific flavonoids and resulted in severely impaired nodulation. Nodule formation was rescued by supplementing the plants with naringenin, which is an upstream intermediate in flavonoid biosynthesis. Our results provide, for the first time, direct evidence of an important role for flavonoids during the early stages of actinorhizal nodulation.
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Khalid
authors.initials: K
authors.lastname: Abdel-Lateif
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Vaissayre
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Hassen
authors.initials: H
authors.lastname: Gherbi
authors.affiliation: INRA, UMR1083 Sciences pour l'Oenologie, F-34060, Montpellier, France.
authors.forename: Clotilde
authors.initials: C
authors.lastname: Verries
authors.affiliation: INRA, UMR1083 Sciences pour l'Oenologie, F-34060, Montpellier, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Meudec
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Francine
authors.initials: F
authors.lastname: Perrine-Walker
authors.affiliation: INRA, UMR1083 Sciences pour l'Oenologie, F-34060, Montpellier, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Cheynier
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Sergio
authors.initials: S
authors.lastname: Svistoonoff
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Claudine
authors.initials: C
authors.lastname: Franche
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Bogusz
authors.affiliation: Equipe Rhizogenèse, UMR DIADE (IRD, UM2), Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex 5, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Hocher
mesh_terms: D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D029962:Fagaceae / Q000201:enzymology* / Q000235:genetics*; D044950:Flavanones / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D017343:Genes, Plant; D010641:Phenotype; D055170:Plant Root Nodulation / Q000235:genetics*; D018517:Plant Roots / Q000166:cytology / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D053719:Tandem Mass Spectrometry; D013997:Time Factors
chemical_list: D044950:Flavanones; D005419:Flavonoids; D000217:Acyltransferases; C020141:flavanone synthetase; C005273:naringenin
keywords: Casuarina glauca; Frankia; RNA interference; actinorhizal symbiosis; chalcone synthase; endosymbiosis; flavonoids; signaling