Regulation of mimosine accumulation in Leucaena leucocephala seedlings

Mimosine is a non-protein amino acid found in the forage legume Leucaena le ucocephala (Lam.) de Wit, which is toxic to animals, has alellopathic effec ts and is an inhibitor of cell division with potential pharmacological appl ications. The regulation of mimosine accumulation in seedlings of L. leucoc ephala during early development, in different parts of seedlings and in res ponse to various chemical and physical factors was examined. Mimosine was e xtracted in acid, purified by paper chromatography, and quantified spectro photometrically through the reaction with p-nitroaniline. The highest mimos ine content was found in the shoots. In etiolated seedlings exposed to ligh t, there was an initial promotion of mimosine accumulation, followed by a r eduction of the amount of the amino acid. Seedlings grown under light and t ransferred to dark had relatively more stable contents of mimosine. The amo unt of mimosine was increased locally by mechanical damage applied to shoot s. Salicylic acid in culture media stimulated mimosine accumulation in root s. During early germination and axillary bud activation for plantlet format ion, there was a significant reduction in mimosine content. The overall res ults indicate that the accumulation of mimosine is regulated by ontogenesis and environmental factors. This suggests that mimosine has adaptive roles. such as an ecochemical agent and a nutritional reserve source. (C) 2001 El sevier Science Ireland Ltd. All rights reserved.