A Diazeniumdiolate Signal in <i>Pseudomonas syringae</i> Upregulates Virulence Factors and Promotes Survival in Plants

<i>Pseudomonas syringae</i> infects a wide variety of crops. The <i>mangotoxin-generating operon</i> (<i>mgo</i>) is conserved across many <i>P. syringae</i> strains and is responsible for producing an extracellular chemical signal, leudiazen. Disruption of the <i>mgoA</i> gene in <i>P. syringae</i> pv. <i>syringae</i> (<i>Pss</i>) UMAF0158 alleviated tomato chlorosis caused by this bacterium. We showed that deletion of the entire <i>mgo</i> reduced <i>Pss</i> UMAF0158 population in tomato leaflets. Leudiazen restored the signaling activity of the deletion mutant at a concentration as low as 10 nM. Both the diazeniumdiolate and isobutyl groups of leudiazen are critical for this potent signaling activity. Transcriptional analysis showed that <i>mgo</i> and leudiazen induce the expression of <i>mangotoxin biosynthetic operon</i> as well as an uncharacterized gene cluster, RS17235-RS17245. We found that this cluster enhances the survival of <i>Pss</i> UMAF0158 in planta and is widely distributed in <i>P. syringae</i> strains. Our results demonstrate that <i>mgo</i> plays prominent roles in the virulence and growth of <i>P. syringae</i>. The <i>mgo</i> and <i>mgo</i>-like signaling systems in different bacteria likely regulate diverse microbe-host interactions. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.