2007 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is to use genetic approaches to identify molecular components and mechanisms that regulate gene expression in Pseudomonas syringae pv. tomato DC3000 (hereafter DC3000), a pathogen of tomato and Arabidopsis. The project will focus primarily on regulatory pathways that are thought to be important in the development of disease. The materials and data generated by this effort will be analyzed by ARS to generate computational models for gene regulation. 1b.Approach (from AD-416) A wide variety of methodologies will be used to dissect gene regulation, and new strategies will be developed as required. The range of possible techniques include the generation, selection and screening of mutants under various conditions, the creation of targeted mutants using molecular methods, and the construction of strains that over-express genes of interest. In addition, the project is likely to employ high throughput techniques such as robotics to aid in the screening of large numbers of strains in parallel, or test the response of DC3000 in multiple environmental conditions. 3.Progress Report This report serves to document research conducted under a Specific Cooperative Agreement between ARS and the Department of Plant Pathology at Cornell University. Additional details can be found in the report for the in-house associated project 1907-21000-027-00D, “Pseudomonas syringae Systems Biology”. Research conducted under this agreement was monitored by weekly meetings between the ADODR and the cooperator. The major accomplishments in this reporting period are: (a) the isolation of a mutant in one of the key genes involved in transcriptional regulation in response to iron bioavailability, PvdS. This mutant strain displays characteristics consistent with a disruption of iron uptake mechanisms. (b) The identification of transcription start sites for seven PvdS-dependent genes. (c) The screening of over 1000 lux reporter transposon insertion mutants to identify genes that respond to the presence of plant-associated compounds.