Production of carbon disillude (CS₂) from L-djenkolic acid in the roots of Mimosa pudica L

• Published in: Plant and soil 1998-03, Vol.200 (1), p.27-32
• Main Authors: Piluk, Jason, Hartel, Peter G., Haines, Bruce L.
• Format: Article
• Language: English
• Subjects: Acid soils; Agricultural soils; Amino acids; Gnotobiotics; Organic soils; Plant roots; Plants; Soil biochemistry; Sulfur; Thiols
• ISSN: 0032-079X; 1573-5036

CS₂ is a volatile liquid with bacteriostatic, fungicidal, nematicidal and insecticidal properties. The roots of some plants, particularly those in the subfamily Mimosoideae, produce CS₂. These plants may have an agronomic use in crop rotations or intercropping because root-produced CS₂ may act as a deterrent to soil pathogens. The biochemical pathway leading to the production of CS₂ from mimosoid roots is unclear. Presumably, S-alkyl cysteine lyases present in mimosoid seedlings hydrolyze L-djenkolic acid, a unique, non-protein, sulfur-containing amino acid, to pyruvate, ammonia and methylene dithiol. Because methylene dithiol 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 from 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 roots were wetted, CS₂ production increased significantly compared to non-wetted roots. When L-djenkolic was applied to injured roots, CS₂ production increased significantly compared to controls. Both thin-layer paper chromatography and high performance liquid chromatography showed 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.