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 pathology, plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to research ...

''. 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 over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s bonded to a

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

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 Hydrophobe, hydrophobic; their odor is usually fain ...

tail. A commonly encountered

pathovar A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one o ...

(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 Cleanliness, cleansing properties when in Concentration, dilute Solution (chemistry), solutions. There are a large variety of detergents. A common family is the alkylbenzene sulfonate ...

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 or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

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

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

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

electrolyte An electrolyte is a substance that conducts electricity through the movement of ions, but not through the movement of electrons. This includes most soluble Salt (chemistry), salts, acids, and Base (chemistry), bases, dissolved in a polar solven ...

and ultimately cell death and

lysis Lysis ( ; from Greek 'loosening') 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 ...

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