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Identification of the syr-syp Box in the Promoter Regions of Genes Dedicated to Syringomycin and Syringopeptin Production by Pseudomonas syringae pv. syringae B301D

Nian Wang,^1, Shi-En Lu,^1, Qingwu Yang,² Sing-Hoi Sze,³ and Dennis C. Gross^1*

Department of Plant Pathology and Microbiology,¹ Department of Computer Science,² Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843³

Received 19 August 2005/ Accepted 10 October 2005

The phytotoxins syringopeptin and syringomycin are synthesized by nonribosomal peptide synthetases which are encoded by the syringomycin (syr) and syringopeptin (syp) genomic island of Pseudomonas syringae pv. syringae. Previous studies demonstrated that expression of the syr-syp genes was controlled by the salA-syrF regulatory pathway, which in turn was induced by plant signal molecules. In this study, the 132-kb syr-syp genomic island was found to be organized into five polycistronic operons along with eight individual genes based on reverse transcriptional PCR and bioinformatic analysis. The transcriptional start sites of the salA gene and operons III and IV were located 63, 75, and 104 bp upstream of the start codons of salA, syrP, and syrB1, respectively, using primer extension analysis. The predicted –10/–35 promoter region of operon IV was confirmed based on deletion and site-directed mutagenesis analyses of the syrB1::uidA reporter with ß-glucuronidase assays. A 20-bp conserved sequence (TGtCccgN₆cggGaCA, termed the syr-syp box) with dyad symmetry around the –35 region was identified via computer analysis for the syr-syp genes/operons responsible for biosynthesis and secretion of syringomycin and syringopeptin. Expression of the syrB1::uidA fusion was decreased 59% when 6 bp was deleted from the 5' end of the syr-syp box in the promoter region of operon IV. These results demonstrate that the conserved promoter sequences of the syr-syp genes contribute to the coregulation of syringomycin and syringopeptin production.

Current address: Plant and Microbial Biology Department, University of California, Berkeley, CA 94720.

Current address: Department of Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762.

This article has been cited by other articles:

• Wang, N., Lu, S.-E., Records, A. R., Gross, D. C. (2006). Characterization of the Transcriptional Activators SalA and SyrF, Which Are Required for Syringomycin and Syringopeptin Production by Pseudomonas syringae pv. syringae. J. Bacteriol. 188: 3290-3298 [Abstract] [Full Text]