Poster: Plant-pathogen interactions

Abs # 506: Developmental disease resistance to the bacterial pathogen Xanthomonas

Presenter:	Bertolet, Bonnie , bertolet@sfsu.edu
Authors	Bertolet, Bonnie  (A)   Yoshikawa, Masayasu  (A)   Deasi, Reena  (A)   Fanter, Rob  (A)   Ponciano, Grisel  (A)   Oyafuso, Alain  (A)   Whalen, Maureen  (A)
Affiliations:	(A): San Francisco State University

Disease resistance to Xanthomonas oryzae pv. oryzae (Xoo) mediated by the resistance gene Xa21 is developmentally controlled in rice. We hypothesize that control of developmental resistance may be mediated by proteins other than XA21. To study activation of defense genes, we cloned OsPR1a, OsPR1b, and OsPR1c genes and analyzed their induction in resistant and susceptible rice lines. At juvenile and adult stages, we assessed the expression pattern of these OsPR1 genes and the PR10a gene in response to a wildtype Xoo strain that induces a resistance response in the Xa21 -line (incompatible interaction) and an isogenic Xoo strain that does not due to a mutation in the raxQ gene (compatible interaction). We found that the developmental stage of rice is important in governing the level of expression of OsPR1 and PR10a defense genes; that is, the adult stage leaves are more competent to express the PR genes. OsPR1b is highly induced in the incompatible interaction between rice and Xoo. OsPR1a and PR10a are also induced but to a lower level. OsPR1a, OsPR1b, OsPR1c and PR10a gene expression in response to wounding was elevated and Xoo suppresses this elevated level of wound-responsive expression in the compatible interaction. We will present our progress toward identifying phosphoproteins that are differentially expressed during the developmental transition from susceptibility to resistance. Our alternate hypothesis is that developmental control may be exerted at Xa21 at the post-transcriptional level. Xa21 does not have an organ-specific expression pattern, however, the level of expression varies from organ to organ. Analysis of levels of XA21protein during development in response to Xoo is underway.