A diffusible factor from arbuscular mycorrhizal fungi induces symbiosis-specific MtENOD11 expression in roots of Medicago truncatula.
Using dual cultures of arbuscular mycorrhizal (AM) fungi and Medicago truncatula separated by a physical barrier, we demonstrate that hyphae from germinating spores produce a diffusible factor that is perceived by roots in the absence of direct physical contact. This AM factor elicits expression of the Nod factor-inducible gene MtENOD11, visualized using a pMtENOD11-gusA reporter. Transgene induction occurs primarily in the root cortex, with expression stretching from the zone of root hair emergence to the region of mature root hairs. All AM fungi tested (Gigaspora rosea, Gigaspora gigantea, Gigaspora margarita, and Glomus intraradices) elicit a similar response, whereas pathogenic fungi such as Phythophthora medicaginis, Phoma medicaginis var pinodella and Fusarium solani f.sp. phaseoli do not, suggesting that the observed root response is specific to AM fungi. Finally, pMtENOD11-gusA induction in response to the diffusible AM fungal factor is also observed with all three M. truncatula Nod(-)/Myc(-) mutants (dmi1, dmi2, and dmi3), whereas the same mutants are blocked in their response to Nod factor. This positive response of the Nod(-)/Myc(-) mutants to the diffusible AM fungal factor and the different cellular localization of pMtENOD11-gusA expression in response to Nod factor versus AM factor suggest that signal transduction occurs via different pathways and that expression of MtENOD11 is differently regulated by the two diffusible factors.
Kosuta
Sonja
S
Equipe Mycologie Végétale, V7R 5546 Centre National de la Recherche Scientifique/Université Toulouse III, Pôle de Biotechnologie Végétale, 24 chemin de Borde-Rouge, 31326 Castanet-Tolosan cedex, France.
Chabaud
Mireille
M
Lougnon
Géraldine
G
Gough
Clare
C
Dénarié
Jean
J
Barker
David G
DG
Bécard
Guillaume
G
D056229:Fungal Structures / Q000254:growth & development / Q000378:metabolism; D005658:Fungi / Q000254:growth & development / Q000378:metabolism; D005670:Fusarium / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D025301:Hyphae / Q000254:growth & development; D029902:Medicago / Q000235:genetics* / Q000382:microbiology; D009154:Mutation; D038821:Mycorrhizae / Q000254:growth & development / Q000378:metabolism*; D010838:Phytophthora / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics* / Q000382:microbiology; D030821:Plants, Genetically Modified; D015398:Signal Transduction / Q000235:genetics; D013172:Spores, Fungal / Q000254:growth & development; D013559:Symbiosis / Q000235:genetics
C438018:ENOD11 protein, Medicago truncatula; D010940:Plant Proteins; D005966:Glucuronidase