Microbial manipulation of host primary metabolism using a type III secreted effector
L. TRIPLETT (1), T. Shidore (2), C. Broeckling (3), J. Kirkwood (3), J. Leach (3) (1) The Connecticut Agricultural Experiment Station, U.S.A.; (2) The Connecticut Agricultural Experiment Station, U.S.A.; (3) Colorado State University, U.S.A.; (4) Colorado State University, U.S.A.

Type III secretion of effector proteins into host cells is a central theme of gram-negative bacterial pathogenesis. Most effectors with a known biochemical activity act through post-translational protein modification or transcriptional activation, although there is evidence that some may act directly on small molecules. AvrRxo1 is a virulence factor and R-gene trigger in the rice pathogen Xanthomonas oryzae pv. oryzicola, with homologs in several species of Xanthomonas, Burkholderia, and Acidovorax. The recent structural characterization of AvrRxo1 revealed similarity to Zeta toxin, a sugar-nucleotide kinase. Hypothesizing that AvrRxo1 might similarly target a small molecule for phosphorylation, we profiled the metabolomes of E. coli, yeast, and tobacco leaf cells expressing AvrRxo1 or a catalytic mutant. In all three cell types, a single detectable metabolite accumulated in AvrRxo1-dependent fashion. A synthetic commercial standard supported MS/MS identification as a phosphorylated molecule not previously detected in nature. An in vitro kinase assay confirmed phosphorylation activity of AvrRxo1 on its predicted substrate, a metabolite with roles in central and secondary metabolism. The product accumulated in rice leaves infected with AvrRxo1-expressing, but not AvrRxo1-deficient, strains of X. oryzae. These results demonstrate that AvrRxo1 is a universal toxin that manipulates central metabolism through a novel kinase activity. 

Abstract Number: C5-2
Session Type: Concurrent