Characterization of four lectin-like receptor kinases expressed in roots of XXXX . Structure, location, regulation of expression, and potential role in the symbiosis with Sinorhizobium meliloti.

@entity958 @entity4166 @entity1568 @entity70632
To study the role of @entity70632 ( @entity70632 ) genes in the legumerhizobia symbiosis, we have characterized the four @entity4166 Gaernt. @entity70632 genes that are most highly expressed in roots. Three of these genes, MtLecRK7;1, MtLecRK7;2, and MtLecRK7;3, encode proteins most closely related to the Class A LecRKs of @entity958 , whereas the protein encoded by the fourth gene, MtLecRK1;1, is most similar to a Class B @entity958 @entity70632 . All four genes show a strongly enhanced root expression, and detailed studies on MtLecRK1;1 and MtLecRK7;2 revealed that the levels of their mRNAs are increased by @entity1568 starvation and transiently repressed after either rhizobial inoculation or addition of lipochitooligosaccharidic Nod factors. Studies of the MtLecRK1;1 and MtLecRK7;2 proteins, using green fluorescent protein fusions in transgenic @entity4166 roots, revealed that they are located in the plasma membrane and that their central transmembrane-spanning helix is required for correct sorting. Moreover, their lectin-like domains appear to be highly glycosylated. Of the four proteins, only MtLecRK1;1 shows a high conservation of key residues implicated in monosaccharide binding, and molecular modeling revealed that this protein may be capable of interacting with Nod factors. However, no increase in Nod factor binding was found in roots overexpressing a fusion in which the kinase domain of this protein had been replaced with green fluorescent protein. Roots expressing this fusion protein however showed an increase in nodule number, suggesting that expression of MtLecRK1;1 influences nodulation. The potential role of LecRKs in the legume-rhizobia symbiosis is discussed.
