Syringomycin

Syringomycin is a general name given to a class of lipodepsinonapeptide molecules which are secreted by the plant pathogen "Pseudomonas syringae". Lipodepsinonapeptides comprise a closed ring of nine nonribosomally-synthesized amino acids bonded to a fatty acid hydrocarbon tail [Scholz-Schroeder B.K., Soule J.D., and Gross D. C. 2003. The sypA, sypS, and sypC synthetase genes encode twenty-two modules involved in the nonribosomal peptide synthesis of syringopeptin by "Pseudomonas syringae" pv. "syringae" B301D. Mol Plant Microbe Interact. 16:271-80] . A commonly-encountered pathovar (pv) of "P. syringae" is "P. syringae" pv "syringae" which secretes a number of closely-related forms of the molecule. Syringomycins are virulence determinants which means that their secretion is required for the manifestation of disease symptoms on a number of stone fruit crop plants.

Syringomycins have two widely-recognized mechanisms of action [Hutchison, M. L., Tester, M. A., and Gross D. C. 1995. Role of biosurfactant and ion channel-forming activities of syringomycin in transmembrane ion flux: A model for the mechanism of action in the plant-pathogen interaction. Mol. Pl. Microb. Interact. 8:610-620.] . They can function as detergents which are powerful enough to dissolve plant membranes at high concentrations. It is not clear whether concentrations high enough to dissolve membranes are ever reached "in planta". In addition to being surfactants, aggregates of syringomycins can insert into plant cell membranes and form small pores. These pores allow the leakage of ions from the plant cell cytoplasm. Affected plant cells are unable to maintain their required levels of electrolyte and ultimately cell death and lysis occurs. It is believed that "P. syringae" benefits from the release of nutrients that occurs as a consequence of cellular lysis.

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