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The Medicago truncatula MtAnn1 Gene Encoding an Annexin Is Induced by Nod Factors and During the Symbiotic Interaction with Rhizobium meliloti

June 1998 , Volume 11 , Number  6
Pages  504 - 513

Fernanda de Carvalho Niebel , Nicole Lescure , Julie V. Cullimore , and Pascal Gamas

Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, INRA-CNRS, UMR 215, BP 27, 31326 Castanet-Tolosan Cedex, France

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Accepted 16 February 1998.

Here we report the characterization of a new Nod factor-induced gene from Medicago truncatula identified by mRNA differential display. This gene, designated MtAnn1, encodes a protein homologous to the annexin family of calcium- and phospholipid-binding proteins. We further show that the MtAnn1 gene is also induced during symbiotic associations with Rhizobium meliloti, both at early stages in bacterial-inoculated roots and in nodule structures. By in situ hybridization, we demonstrate that MtAnn1 expression in nodules is mainly associated with the distal region of invasion zone II not containing infection threads, revealing MtAnn1 as a new marker gene of the pre-infection zone. Moreover, analyses of MtAnn1 expression in response to bacterial symbiotic mutants suggest that the expression of MtAnn1 during nodulation requires biologically active Nod factors and is independent of the infection process.

Additional keywords: supernodulating mutant line, symbiosis.

© 1998 The American Phytopathological Society