Characterization of Four Lectin-Like Receptor Kinases Expressed in Roots of Medicago truncatula. Structure, Location, Regulation of Expression, and Potential Role in the Symbiosis with Sinorhizobium meliloti

• DOI: 10.1104/pp.103.027680
• Publication Date: 2003-12-17T23:23:11Z
• Authors: Maria-Téresa Nav...; Sylvie Camut; Antonius C.J. Tim...; Andreas Niebel; Christine Hervé; Emmanuel Boutet; Jean-Jacques Bono; Anne Imberty; Julie V. Cullimore
• Keywords: Medicago truncatula; Nod factor; Sinorhizobium meliloti

Abstract To study the role of LecRK (lectin-like receptor kinase) genes in legumerhizobia symbiosis, we have characterized four Medicago truncatula Gaernt. that are most highly expressed roots. Three these genes, MtLecRK7;1, MtLecRK7;2, and MtLecRK7;3, encode proteins closely related to Class A LecRKs Arabidopsis, whereas protein encoded by fourth gene, MtLecRK1;1, is similar a B Arabidopsis LecRK. All show strongly enhanced root expression, detailed studies on MtLecRK1;1 MtLecRK7;2 revealed levels their mRNAs increased nitrogen starvation transiently repressed after either rhizobial inoculation or addition lipochitooligosaccharidic Nod factors. Studies proteins, using green fluorescent fusions transgenic M. roots, they located plasma membrane central transmembrane-spanning helix required for correct sorting. Moreover, lectin-like domains appear be glycosylated. Of only shows high conservation key residues implicated monosaccharide binding, molecular modeling this may capable interacting with However, no increase factor binding was found roots overexpressing fusion which kinase domain had been replaced protein. Roots expressing however showed an nodule number, suggesting expression influences nodulation. The potential legume-rhizobia symbiosis discussed.