1. The Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
2. Kazusa DNA Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan
3. Laboratory of Gene Expression, IMSB, University of Aarhus, Gustav Wieds Vej 10, DK-8000 Aarhus C, Denmark
4. Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, 1391 Sandford Street, London, Ontario N5V 4T3, Canada

Correspondence to: Martin Parniske¹ Correspondence and requests for materials should be addressed to M.P. (e-mail: Email: martin.parniske@bbsrc.ac.uk). Sequences are deposited at GenBank with the following accession numbers. Lotus SYMRK, AF492655; pea SYM19, AF491997; M. truncatula SYMRK, AF491998. TAC clones: Lotus T11E23 (containing the Lotus SYMRK gene), AP004579; Lotus T01N11, AP004576; Lotus T10N22, AP004577; Lotus T17H01, AP004578.

Abstract

Most higher plant species can enter a root symbiosis with arbuscular mycorrhizal fungi, in which plant carbon is traded for fungal phosphate^{1, 2}. This is an ancient symbiosis, which has been detected in fossils of early land plants³. In contrast, the nitrogen-fixing root nodule symbioses of plants with bacteria evolved more recently, and are phylogenetically restricted to the rosid I clade of plants⁴. Both symbioses rely on partially overlapping genetic programmes^{5, 6}. We have identified the molecular basis for this convergence by cloning orthologous SYMRK ('symbiosis receptor-like kinase') genes from Lotus and pea, which are required for both fungal and bacterial recognition. SYMRK is predicted to have a signal peptide, an extracellular domain comprising leucine-rich repeats, a transmembrane and an intracellular protein kinase domain. Lotus SYMRK is required for a symbiotic signal transduction pathway leading from the perception of microbial signal molecules to rapid symbiosis-related gene activation. The perception of symbiotic fungi and bacteria is mediated by at least one common signalling component, which could have been recruited during the evolution of root nodule symbioses from the already existing arbuscular mycorrhiza symbiosis.

1. The Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
2. Kazusa DNA Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan
3. Laboratory of Gene Expression, IMSB, University of Aarhus, Gustav Wieds Vej 10, DK-8000 Aarhus C, Denmark
4. Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, 1391 Sandford Street, London, Ontario N5V 4T3, Canada

Correspondence to: Martin Parniske¹ Correspondence and requests for materials should be addressed to M.P. (e-mail: Email: martin.parniske@bbsrc.ac.uk). Sequences are deposited at GenBank with the following accession numbers. Lotus SYMRK, AF492655; pea SYM19, AF491997; M. truncatula SYMRK, AF491998. TAC clones: Lotus T11E23 (containing the Lotus SYMRK gene), AP004579; Lotus T01N11, AP004576; Lotus T10N22, AP004577; Lotus T17H01, AP004578.