Enhancing Disease Resistance in Rice

Photo credit info: IRRI/Flickr

The Ronald lab studies the innate immune response, using the host organism rice and the agriculturally important pathogen Xanthomonas oryzae pv. oryzae (Xoo). In the 1990s, rice geneticist Gurdev Khush and colleagues identified a wild species of rice, Oryza longistaminata, which conferred broad-spectrum resistance to Xoo. Khush showed that a single genetic locus, which he named XA21 (Xanthomonas resistance 21) was responsible for the resistance. Ronald  hypothesized that Xa21 encoded a single protein that recognized a conserved microbial determinant.

In 1995, the Ronald laboratory isolated and characterized the rice XA21 genetic locus and showed that XA21 encodes a receptor kinase (aka pattern recognition receptor.) Subsequent discoveries in flies, humans, mice, and Arabidopsis revealed that animals and other plant species also carry membrane-anchored receptors with striking structural similarities to XA21 and that these receptors also play key roles in the immune response. The significance of these discoveries was highlighted by the 2011 Nobel Prize in Medicine awarded to Jules Hoffman and Bruce Beutler, (jointly with Ralph Steinman), for their discoveries of the fly and mice receptors. In 2015, Ronald and team reported the isolation of the predicted ligand of XA21, a sulfated peptide named RaxX.[1][2][3]



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