title: The MtMMPL1 early nodulin is a novel member of the matrix metalloendoproteinase family with a role in Medicago truncatula infection by Sinorhizobium meliloti.
abstract: We show here that MtMMPL1, a Medicago truncatula nodulin gene previously identified by transcriptomics, represents a novel and specific marker for root and nodule infection by Sinorhizobium meliloti. This was established by determining the spatial pattern of MtMMPL1 expression and evaluating gene activation in the context of various plant and bacterial symbiotic mutant interactions. The MtMMPL1 protein is the first nodulin shown to belong to the large matrix metalloendoproteinase (MMP) family. While plant MMPs are poorly documented, they are well characterized in animals as playing a key role in a number of normal and pathological processes involving the remodeling of the extracellular matrix. MtMMPL1 represents a novel MMP variant, with a substitution of a key amino acid residue within the predicted active site, found exclusively in expressed sequence tags corresponding to legume MMP homologs. An RNA interference approach revealed that decreasing MtMMPL1 expression leads to an accumulation of rhizobia within infection threads, whose diameter is often significantly enlarged. Conversely, MtMMPL1 ectopic overexpression under the control of a constitutive (35S) promoter led to numerous abortive infections and an overall decrease in the number of nodules. We discuss possible roles of MtMMPL1 during Rhizobium infection.
authors.affiliation: Laboratoire des Interactions Plantes Micro-organismes, Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique, 31326 Castanet Tolosan cedex, France.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Combier
authors.forename: Tatiana
authors.initials: T
authors.lastname: Vernié
authors.forename: Françoise
authors.initials: F
authors.lastname: de Billy
authors.forename: Fikri
authors.initials: F
authors.lastname: El Yahyaoui
authors.forename: René
authors.initials: R
authors.lastname: Mathis
authors.forename: Pascal
authors.initials: P
authors.lastname: Gamas
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D046913:Medicago truncatula / Q000201:enzymology* / Q000382:microbiology; D008969:Molecular Sequence Data; D034622:RNA Interference; D053204:Root Nodules, Plant / Q000201:enzymology* / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000502:physiology*; D013559:Symbiosis / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D020782:Matrix Metalloproteinases