Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/27/2007
Publication Date: 8/1/2007
Citation: Ponciano, G., Masayasu, Y., Lee, J., Ronald, P., Whalen, M.C. 2007. Pathogenesis-Related Gene Expression in Rice is Correlated with Developmentally Controlled Xa21-mediated Resistance against Xanthomonas oryzae pv. oryzae. Physiological and Molecular Plant Pathology. 69: 131-139. Interpretive Summary: Most rice plants are susceptible to bacterial wilt disease caused by the bacterial pathogen, Xanthomonas oryzae pathovar oryzae, called Xoo. Rice plants containing the disease resistance gene Xa21 are resistance to Xoo, but only at the adult stage of development. We are interested in understanding the molecular basis of this phenomenon in order to engineer rice plants that are resistant at all developmental stages. We examined the relationship between expression of defense protein genes, called PR1a, PR1b, PR1c and PR10a genes, and developmental resistance in rice lines with and without Xa21. We found that the developmental stage of rice is important in governing the level of expression of these defense genes; that is, the adult stage leaves are more competent than juvenile stage leaves to express the PR1a and PR1b genes in resistant lines.
Technical Abstract: Disease resistance mediated by the resistance gene Xa21 is developmentally controlled in rice. We examined the relationship between pathogenesis related (PR) defense gene expression and Xa21-mediated developmental disease resistance induced by Xanthomonas oryzae pv. oryzae (Xoo). OsPR1a, OsPR1b, and OsPR1c genes were cloned and their induction was analyzed, in addition to the PR10a gene, at the juvenile and adult stages in response to a wildtype Xoo strain that induces a resistance response (incompatible interaction) and an isogenic mutant Xoo strain that does not (compatible interaction). We found that the adult stage leaves are more competent to express these PR1 genes. Xa21 is required for the highest levels of induction and there is induction in the absence of avrXa21 activity, suggesting the involvement of PR1 proteins in basal resistance.