ISOLATION OF A CDNA-ENCODING A NOVEL LEUCINE-RICH REPEAT MOTIF FROM SORGHUM-BICOLOR INOCULATED WITH FUNGI

A sorghum cDNA clone has been isolated that encodes a protein containi ng six imperfect leucine-rich repeats (LRRs) of approximately 22 amino acids in length. The putative protein, designated SLRR, also contains a signal peptide, and six potential N-glycosylation sites, Comparison s of SLRR and its LRR consensus sequences found significant homology t o the extracellular binding domains of receptor-protein kinases RLK5 a nd TMK1 of Arabidopsis, and some plant disease resistance genes, Resul ts from RNA gel blot analyses showed that SLRR mRNA accumulates rapidl y in mesocotyls and juvenile leaves by 6 h postinoculation with the fu ngus Colletotricum graminicola, Further experiments suggest that the g ene encoding SLRR is neither systemically induced by fungal inoculatio n, nor transcriptionally activated in a host-fungal-pathogen-specific manner, The presence of LRRs strongly suggests that the SLRR protein i s involved in protein-ligand binding and therefore may be a component of a signal transduction pathway.