PRODUCTION OF CARBON-DISULFIDE (CS2) FROM L-DJENKOLIC ACID IN THE ROOTS OF MIMOSA-PUDICA L

CS2 is a volatile liquid with bacteriostatic, fungicidal, nematicidal and insecticidal properties. The roots of some plants, particularly th ose in the subfamily Mimosoideae, produce CS2. These plants may have a n agronomic use in crop rotations or intercropping because root-produc ed CS2 may act as a deterrent to soil pathogens. The biochemical pathw ay leading to the production of CS2 from mimosoid roots is unclear. Pr esumably, S-alkyl cysteine lyases present in mimosoid seedlings hydrol yze L-djenkolic acid, a unique, non-protein, sulfur-containing amino a cid, to pyruvate, ammonia and methylene dithiol. Because methylene dit hiol has never been detected from mimosoid roots, we hypothesized that CS2 is produced instead. Mimosa pudica, a species which produces CS2 in its roots, was used as a model plant. To eliminate CS2 production f rom microbial sources, all plants were grown gnotobiotically. S-alkyl cysteine lyase activity was confirmed in M. pudica when PbS formed on injured roots treated with L-cysteine and lead acetate. When injured r oots were wetted, CS2 production increased significantly compared to n on-wetted roots. When L-djenkolic was applied to injured roots, CS2 pr oduction increased significantly compared to controls. Both thin-layer paper chromatography and high performance liquid chromatography showe d the presence of L-djenkolic acid in root tissues of M. pudica. These findings suggest CS2 production in roots of M. pudica occurs via the hydrolysis of L-djenkolic acid by S-alkyl cysteine lyase.