Abstract
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 Verticillium longisporum, Fusarium graminearum and Sclerotinia sclerotiorum, the plant symbiotic fungal endophyte Serendipita indica, the bacterial pathogens Pseudomonas syringae pv. tomato (Pst), Agrobacterium tumefaciens, and the related beneficial strain Rhizobium radiobacter. Phytosphingosine inhibited growth of these organisms at micromolar concentrations. Among the fungal pathogens, S. sclerotiorum was the most, and F. graminearum was the least sensitive. 15.9 μg/mL phytosphingosine effectively killed 95% of the three bacterial species. Plant disease symptoms and growth of Pst 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.
Highlights
Sphingolipid long chain bases (LCBs) are building blocks of sphingolipids and can serve as signalling molecules, and have antimicrobial activity and were effective in reducing growth of a range of human pathogens
Programmed cell death in Arabidopsis thaliana induced by recognition of an avirulence protein of the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) leads to elevated levels of the LCB p hytosphingosine[9]
All fungi were negatively affected in mycelial growth by the presence of t18:0, indicated by analysis of variance (ANOVA; p < 0.001) for the effect of t18:0, with the factor ‘time’ as a covariate
Summary
Sphingolipid long chain bases (LCBs) are building blocks of sphingolipids and can serve as signalling molecules, and have antimicrobial activity and were effective in reducing growth of a range of human pathogens. Sphingolipids are formed by linking this amine group to a fatty acid (with chain lengths between 14 and 26 carbon atoms), and further modifications, e.g. sugar residues and/or phosphate groups linked to the C1 position Beside their role for sphingolipid biosynthesis, LCBs can function as intra- and intercellular signal transduction molecules. Antimicrobial activity of LCBs was shown for a range of gram-positive and negative bacteria, among them human pathogens (such as Pseudomonas aeruginosa or Neisseria meningitidis) and Escherichia coli strains, and fungal species such as Candida albicans[14,15,16,17,18]. We aimed to test the antimicrobial effect of phytosphingosine on those bacterial and fungal species interacting with plants
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