title: Auxin influx activity is associated with Frankia infection during actinorhizal nodule formation in Casuarina glauca.
abstract: Plants from the Casuarinaceae family enter symbiosis with the actinomycete Frankia leading to the formation of nitrogen-fixing root nodules. We observed that application of the auxin influx inhibitor 1-naphtoxyacetic acid perturbs actinorhizal nodule formation. This suggests a potential role for auxin influx carriers in the infection process. We therefore isolated and characterized homologs of the auxin influx carrier (AUX1-LAX) genes in Casuarina glauca. Two members of this family were found to share high levels of deduced protein sequence identity with Arabidopsis (Arabidopsis thaliana) AUX-LAX proteins. Complementation of the Arabidopsis aux1 mutant revealed that one of them is functionally equivalent to AUX1 and was named CgAUX1. The spatial and temporal expression pattern of CgAUX1 promoter:beta-glucuronidase reporter was analyzed in Casuarinaceae. We observed that CgAUX1 was expressed in plant cells infected by Frankia throughout the course of actinorhizal nodule formation. Our data suggest that auxin plays an important role during plant cell infection in actinorhizal symbioses.
authors.affiliation: Unité Mixte de Recherche Diversité et Adaptation des Plantes Cultivées , Equipe Rhizogenèse, 34394 Montpellier cedex 5, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Péret
authors.forename: Ranjan
authors.initials: R
authors.lastname: Swarup
authors.forename: Leen
authors.initials: L
authors.lastname: Jansen
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Devos
authors.forename: Florence
authors.initials: F
authors.lastname: Auguy
authors.forename: Myriam
authors.initials: M
authors.lastname: Collin
authors.forename: Carole
authors.initials: C
authors.lastname: Santi
authors.forename: Valérie
authors.initials: V
authors.lastname: Hocher
authors.forename: Claudine
authors.initials: C
authors.lastname: Franche
authors.forename: Didier
authors.initials: D
authors.lastname: Bogusz
authors.forename: Malcolm
authors.initials: M
authors.lastname: Bennett
authors.forename: Laurent
authors.initials: L
authors.lastname: Laplaze
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D040161:Frankia / Q000502:physiology*; D015870:Gene Expression; D017343:Genes, Plant; D005816:Genetic Complementation Test; D006016:Glycolates / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019684:Magnoliopsida / Q000378:metabolism / Q000382:microbiology* / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D053204:Root Nodules, Plant / Q000378:metabolism / Q000382:microbiology* / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis / Q000502:physiology*
chemical_list: C100794:AUX1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D006016:Glycolates; D007210:Indoleacetic Acids; C018610:1-naphthoxyacetic acid