Syringomycin E is a member of a class of lipodepsinonapeptide molecules that are secreted by the plant pathogen ''

Pseudomonas syringae ''Pseudomonas syringae'' is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from internat ...

''. Lipodepsinonapeptides comprise a closed ring of nine nonribosomally synthesized

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s bonded to a

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

tail. 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. They can function as

detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...

s 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 membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

s and form small pores. These pores allow the leakage of ions from the plant cell

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

. Affected plant cells are unable to maintain their required levels of

electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

and ultimately cell death and

lysis Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular bio ...

occurs. It is believed that ''P. syringae'' benefits from the release of nutrients that occurs as a consequence of cellular lysis. The biosynthesis of this class of molecules has been elucidated.Blasiak, L. C., Vaillancourt, F. d. r. H., Walsh, C. T., Drennan, C. L., "Crystal structure of the non-haem iron halogenase SyrB2 in syringomycin biosynthesis", Nature 2006, 440, 368.

References

{{Non-ribosomally synthesized channels Plant toxins Cyclic peptides