Publication no. M-2002-0506-02R

Microarray Profiling of Erwinia chrysanthemi 3937 Genes That are Regulated During Plant Infection. Yasushi Okinaka (1), Ching-Hong Yang (1), Nicole T. Perna (2), and Noel. T. Keen (1). (1) Department of Plant Pathology and Center for Plant Cell Biology, University of California, Riverside 92521, U.S.A; (2) Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison 53706, U.S.A. MPMI 15:619-629. Submitted 18 March 2002. Accepted 28 March 2002. Copyright 2002 The American Phytopathological Society.

Microarray technology was used to identify genes in Erwinia chrysanthemi 3937 that are specifically up- or down-regulated in a plant host compared with growth in laboratory culture medium. Several genes were plant down-regulated, and almost all of them were homologues of well-known housekeeping genes, such as those encoding metabolic functions, oxidative phosphorylation components, and transcription or translation processes. On the other hand, almost all of the plant up-regulated genes were involved with specialized functions, including already known or new putative virulence factors, anaerobiosis, iron uptake, transporters or permeases, xenobiotic resistance, chemotaxis, and stress responses to reactive oxygen species and heat. A substantial number of the plant up-regulated genes do not appear to be directly involved in damaging the host, but are probably important in adapting the pathogen to the host environment. We constructed insertion mutations in several of the plant up-regulated E. chrysanthemi 3937 genes. Among these, mutations of Bacillus subtilis pps1, Escherichia coli purU, and Pseudomonas aeruginosa pheC homologues reduced virulence on African violet leaves. Thus, new insights were obtained into genes important in bacterial virulence.