Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Sphingolipid long chain bases (LCBs) are building blocks of sphingolipids and can serve as signalling molecules, but also have antimicrobial activity and were effective in reducing growth of a range of human pathogens. In plants, LCBs are linked to cell death processes and the regulation of defence reactions against pathogens, but their role in directly influencing growth of plant-interacting microorganisms has received little attention. Therefore, we tested the major plant LCB phytosphingosine in in vitro tests with the plant pathogenic fungi <jats:italic>Verticillium longisporum</jats:italic>, <jats:italic>Fusarium graminearum</jats:italic> and <jats:italic>Sclerotinia sclerotiorum</jats:italic>, the plant symbiotic fungal endophyte <jats:italic>Serendipita indica</jats:italic>, the bacterial pathogens <jats:italic>Pseudomonas syringae</jats:italic> pv. <jats:italic>tomato</jats:italic> (<jats:italic>Pst</jats:italic>), <jats:italic>Agrobacterium tumefaciens</jats:italic>, and the related beneficial strain <jats:italic>Rhizobium radiobacter</jats:italic>. Phytosphingosine inhibited growth of these organisms at micromolar concentrations. Among the fungal pathogens, <jats:italic>S. sclerotiorum</jats:italic> was the most, and <jats:italic>F. graminearum</jats:italic> was the least sensitive. 15.9 μg/mL phytosphingosine effectively killed 95% of the three bacterial species. Plant disease symptoms and growth of <jats:italic>Pst</jats:italic> were also inhibited by phytosphingosine when co-infiltrated into Arabidopsis leaves, with no visible negative effect on host tissue. Taken together, we demonstrate that the plant LCB phytosphingosine inhibits growth of plant-interacting microorganisms. We discuss the potential of elevated LCB levels to enhance plant pathogen resistance.</jats:p>