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Investigating the Role of Trehalose Metabolism During Ralstonia solanacearum Bacterial Wilt Disease

April MacIntyre: University of Wisconsin-Madison

<div><em>Ralstonia solanacearum</em> (<em>Rs</em>) is a xylem-dwelling pathogen that causes bacterial wilt disease. Unknown metabolic strategies enable <em>Rs</em> to exploit its harsh, nutrient poor niche. Comparative metabolomic analysis revealed that xylem trehalose levels increased 16-fold upon <em>Rs</em> infection. This disaccharide plays many roles in plants and bacteria, including stress tolerance and signaling. <em>Rs</em> and host tomato plants both have multiple pathways to synthesize and degrade trehalose. During <em>Rs </em>infection, a tomato trehalose-6-phosphate (T6P) synthase gene is upregulated, indicating that disease alters host trehalose metabolism. On the pathogen side, transcriptional analyses showed that the <em>Rs</em> trehalase gene, <em>treA</em>, is highly upregulated during bacterial wilt disease<em>.</em> <em>Rs </em>Δ<em>treA</em> cannot grow on trehalose as a sole carbon source, and cannot colonize tomato plants as well as wild-type<em>. </em>Together, these observations suggest that<em> trehalose metabolism in tomato and </em>Rs<em> contributes to bacterial virulence and fitness during disease. </em>We are testing this hypothesis using a suite of <em>Rs </em>altered trehalose metabolism mutants, including strains lacking one or more of the pathogen’s three trehalose synthetic pathways, and a type 3 effector with T6P activity. We will determine the effect of these mutations on <em>Rs</em> stress tolerance, xylem sugar levels, competitive fitness <em>in planta</em>, and virulence. This is the first study of trehalose biology in the context of a natural host for this destructive pathogen.</div>