A Medicago truncatula mutant hyper-responsive to mycorrhiza and defective for nodulation.
One key strategy for the identification of plant genes required for mycorrhizal development is the use of plant mutants affected in mycorrhizal colonisation. In this paper, we report a new Medicago truncatula mutant defective for nodulation but hypermycorrhizal for symbiosis development and response. This mutant, called B9, presents a poor shoot and, especially, root development with short laterals. Inoculation with Glomus intraradices results in significantly higher root colonisation of the mutant than the wild-type genotype A17 (+20% for total root length, +16% for arbuscule frequency in the colonised part of the root, +39% for arbuscule frequency in the total root system). Mycorrhizal effects on shoot and root biomass of B9 plants are about twofold greater than in the wild-type genotype. The B9 mutant of M. truncatula is characterised by considerably higher root concentrations of the phytoestrogen coumestrol and by the novel synthesis of the coumestrol conjugate malonyl glycoside, absent from roots of wild-type plants. In conclusion, this is the first time that a hypermycorrhizal plant mutant affected negatively for nodulation (Myc(++), Nod (-/+) phenotype) is reported. This mutant represents a new tool for the study of plant genes differentially regulating mycorrhiza and nodulation symbioses, in particular, those related to autoregulation mechanisms.
UMR INRA 1088/CNRS 5184/Université de Bourgogne Plante-Microbe-Environnement, INRA-CMSE, BP 86510, 21065, Dijon Cedex, France. morandi@dijon.inra.fr.
Dominique
D
Morandi
UMR Génétique et Ecophysiologie des Légumineuses à Graines, INRA, BP 86510, 21065, Dijon Cedex, France.
Christine
C
le Signor
UMR INRA 1088/CNRS 5184/Université de Bourgogne Plante-Microbe-Environnement, INRA-CMSE, BP 86510, 21065, Dijon Cedex, France.
Vivienne
V
Gianinazzi-Pearson
UMR Génétique et Ecophysiologie des Légumineuses à Graines, INRA, BP 86510, 21065, Dijon Cedex, France.
Gérard
G
Duc
D018533:Biomass; D003375:Coumestrol / Q000032:analysis; D055137:Glomeromycota / Q000254:growth & development*; D046913:Medicago truncatula / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D009154:Mutation; D038821:Mycorrhizae / Q000254:growth & development*; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development / Q000382:microbiology*; D018520:Plant Shoots / Q000254:growth & development
D003375:Coumestrol