Beschreibung:
<jats:title>Summary</jats:title><jats:p><jats:styled-content style="fixed-case"><jats:italic>Y</jats:italic></jats:styled-content><jats:italic>ersinia enterocolitica</jats:italic> is toxic towards invertebrates due to the presence of the toxin complex (<jats:styled-content style="fixed-case"><jats:italic>tc</jats:italic></jats:styled-content>) genes that are activated by the thermolabile regulator <jats:styled-content style="fixed-case">TcaR</jats:styled-content>2. In the search for further regulatory factors involved in insecticidal gene expression, the modulator of yersinial virulence, <jats:styled-content style="fixed-case">YmoA</jats:styled-content>, was identified to silence all <jats:styled-content style="fixed-case"><jats:italic>tc</jats:italic></jats:styled-content> genes of the <jats:styled-content style="fixed-case"><jats:italic>Y</jats:italic></jats:styled-content><jats:italic>. enterocolitica</jats:italic> strain <jats:styled-content style="fixed-case">W</jats:styled-content>22703 (biovar 2, serovar <jats:styled-content style="fixed-case">O</jats:styled-content>:9). Using promoter fusions with the luciferase reporter, we found that the deletion of <jats:styled-content style="fixed-case"><jats:italic>ymoA</jats:italic></jats:styled-content> results in elevated transcription of <jats:styled-content style="fixed-case"><jats:italic>tcaR1</jats:italic></jats:styled-content>, <jats:styled-content style="fixed-case"><jats:italic>tcaR2</jats:italic></jats:styled-content>, <jats:styled-content style="fixed-case"><jats:italic>tcaA</jats:italic></jats:styled-content>, <jats:styled-content style="fixed-case"><jats:italic>tcaB</jats:italic></jats:styled-content>, <jats:styled-content style="fixed-case"><jats:italic>tcaC</jats:italic></jats:styled-content>, <jats:styled-content style="fixed-case"><jats:italic>tccC1</jats:italic></jats:styled-content> and <jats:styled-content style="fixed-case"><jats:italic>tccC2</jats:italic></jats:styled-content> at both 15°<jats:styled-content style="fixed-case">C</jats:styled-content> and 37°<jats:styled-content style="fixed-case">C</jats:styled-content>. Complementation by episomal <jats:styled-content style="fixed-case"><jats:italic>ymoA</jats:italic></jats:styled-content> significantly reduced <jats:styled-content style="fixed-case"><jats:italic>tc</jats:italic></jats:styled-content> gene expression, thus validating the inhibitory activity of <jats:styled-content style="fixed-case">YmoA</jats:styled-content> on the production of insecticidal proteins. <jats:styled-content style="fixed-case">YmoA</jats:styled-content> contributes to the binding properties of <jats:styled-content style="fixed-case">H</jats:styled-content>‐<jats:styled-content style="fixed-case">NS</jats:styled-content> to the <jats:styled-content style="fixed-case"><jats:italic>tc</jats:italic></jats:styled-content> promoters by forming a complex with this nucleoid‐associated protein, and this complex not only binds to the upstream regions of all <jats:styled-content style="fixed-case"><jats:italic>tc</jats:italic></jats:styled-content> genes, but also to intragenic sites of <jats:styled-content style="fixed-case"><jats:italic>tcaA</jats:italic></jats:styled-content> and <jats:styled-content style="fixed-case"><jats:italic>tcaB</jats:italic></jats:styled-content> that play an important role in controlling the expression of both genes. At low temperature, the intracellular amount of thermostable <jats:styled-content style="fixed-case">YmoA</jats:styled-content> is not reduced, but the repressor is less functional. These data point to <jats:styled-content style="fixed-case">H</jats:styled-content>‐<jats:styled-content style="fixed-case">NS</jats:styled-content>/<jats:styled-content style="fixed-case">YmoA</jats:styled-content> as an antagonist of the inducer <jats:styled-content style="fixed-case">TcaR</jats:styled-content>2.</jats:p>