Effect of environmental factors on the biosynthesis of the neuro-excitatory amino acid β-ODAP (β-N-oxalyl-L-α,β-diaminopropionic acid) in callus tissue of Lathyrus sativus.

Habituated callus tissues derived from leaf explants of Lathyrus sativus L. (grass pea) were cultured under different environmental conditions such as drought, salinity and deficiency or oversupply of micronutrients. The biosynthesis of the neuro-excitatory β-ODAP (β-N-oxalyl-L-α,β-diaminopropionic acid) was induced by feeding the precursor BIA, (β-isoxazolin-5-on-2-yl)-alanine, to those calli habituated under different stress conditions. Conversion of BIA into β-ODAP was reduced by Zn(2+) at different levels of Fe(2+) supplements while excess of Fe(2+) enhanced it at different Zn(2+) levels in the media. The biosynthesis of β-ODAP was increased by both oversupply and deficiency of Mn(2+) manganese while B(3+) as well as Co(2+) increased it significantly by oversupply. Al(3+) enhanced the conversion of BIA into β-ODAP significantly in a concentration-dependent way. Cu(2+) also reduced the formation of β-ODAP when increased in the media. Mo(6+) had no apparent effect. NaCl decreased the conversion of BIA into β-ODAP proportionately with the increase in salinity. β-ODAP was increased with increasing mannitol concentration till -0.23MPa while at this osmotic potential created with PEG-20,000 the formation of β-ODAP is completely inhibited in low toxin calli. These experiments demonstrate the importance of environmental factors, especially micronutrients and salinity, on the biosynthesis of β-ODAP.