Plant, Animal & Microbe Genomes X Conference

January 12-16, 2002
Town & Country Convention Center
San Diego, CA

Session: Microbe Session Lecture
            

PSEUDOMONAS SYRINGAE PV. TOMATO DC3000: GENOMICS AND PHYTOPATHOGENICITY

¹ Department of Plant Pathology, Cornell University, Ithaca, NY 14083-4203

² Plant Science Initiative, Center for Biotechnology, University of Nebraska – Lincoln, NE 68588-0665

³ Department of Eukaryotic Genomics, The Institute for Genomic Research, 9712 Medical Center Dr., Rockville, MD 20850

⁴ Center for Agricultural Bioinformatics, Cornell Theory Center, Ithaca, NY 14853

⁵ Department of Plant Pathology, University of Missouri, Columbia, MO 65211

⁶ Boyce Thompson Institute for Plant Research and Department of Plant Pathology, Cornell University, Ithaca, NY 14853-1801

⁷ Department of Plant Pathology, Kansas State University, Manhattan, KS 66502-5502

The NSF Plant Genome Program funded a Pseudomonas-Plant Interaction project to study the sequence and function of the P. s. tomato DC3000 genome. Genomic sequencing at The Institute for Genomic Research (TIGR) achieved 8x coverage January 2001 and is now in closure phase. Project information and data can be accessed at http://ppi.cornell.edu and http://www.tigr.org/tdb/mdb/mdbinprogress.html. P. s. tomato DC3000 pathogenesis in tomato and Arabidopsis is dependent upon genes activated by the HrpL alternative sigma factor. We used an iterative process involving computational and gene expression techniques to identify virulence-implicated genes downstream of HrpL-responsive promoters. This process involved reporter transposon mutagenesis, development of a Hidden Markov Model (HMM) trained with known and transposon-identified Hrp promoter sequences, HMM identification of promoters upstream of additional virulence-implicated genes, and microarray and RNA blot analyses of the HrpL-dependent expression of a representative subset of these DC3000 genes. We found that the Hrp regulon encodes multiple candidate Hrp (type III protein secretion) machinery accessory factors, homologs of the Hrp effector proteins HopPsyA, AvrPpiB1 AvrPpiC2, AvrPphD, AvrPphE, AvrPphF, and AvrXv3, and genes associated with the production or metabolism of virulence factors unrelated to the Hrp secretion system, including syringomycin synthetase (SyrE), N-epsilon-(indole-3-acetyl)-L-lysine synthetase (IaaL), and a subsidiary regulon controlling coronatine production. Further project objectives include identification of additional Hrp effectors and virulence regulons, investigation of pathogen-plant interactions by cell biological and microarray analyses, and comparison of the genomes of P. syringae, P. aeruginosa, and P. putida.