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Identification and characterization of a carbonic anhydrase involved in virulence and bacterial competition of Pseudomonas syringae pv. tomato DC3000

Melanie Filiatrault: USDA ARS

<div>Carbonic anhydrases play important roles in balancing pH, lipid biogenesis, calcification, and pathogenesis of bacteria. We recently discovered a gene (<em>cynT</em>) in the plant pathogenic bacterium <em>Pseudomonas syringae</em> pv. <em>tomato</em> DC3000 (<em>Pto</em>) that encodes a putative carbonic anhydrase. To determine the role of <em>cynT </em>in <em>Pto</em>, we investigated the transcriptional regulation and the impact of deleting this gene in <em>Pto</em>. Bioinformatics analysis identified alternative transcripts in the 5’ UTR of <em>cynT</em> as well as a predicted binding site for the sigma factor RpoF within the promoter region. We demonstrate that RpoF regulates transcription of <em>cynT </em>and a putative small RNA is produced within this genomic location. A ∆<em>cynT</em> strain displayed reduced symptoms and growth in tomato plants and showed a delay in the hypersensitive response in <em>Nicotiana</em> <em>benthamiana.</em> Furthermore, we show that <em>cynT </em>controls cellulose production in <em>Pto</em> and affects bacterial competition of <em>Pto</em> with other bacteria. Our data support a role of <em>cynT</em> in deployment of effectors into host cells and other bacterial cells, linking <em>cynT</em> to regulation of the Type III and VI secretion systems. The involvement of <em>cynT</em> in critical steps of the <em>Pto</em> life cycle suggests an important role for carbonic anhydrases during bacterial plant-pathogen interactions. Since carbonic anhydrases are conserved among bacterial plant pathogens, these enzymes represent promising new targets for the development of anti-bacterial agents.</div>