Protein association of -N-methylamino-L-alanine in Triticum aestivum via irrigation

Bioaccumulation of several cyanotoxins has been observed in numerous food webs. More recently, the neurotoxic, non-proteinogenic amino acid -N-methylamino-L-alanine (BMAA) was shown to biomagnify in marine food webs. It was thus necessary to assess whether a human exposure risk via a terrestrial food source could exist. As shown for other cyanotoxins, spray irrigation of crop plants with cyanobacterial bloom-contaminated surface water poses the risk of toxin transfer into edible plant parts. Therefore, in the present study, we evaluated a possible transfer of BMAA via spray irrigation into the seeds of one of the world's most widely cultivated crop plants, Triticum aestivum. Wheat plants were irrigated with water containing 10 mu g L-1 BMAA until they reached maturity and seed-bearing stage (205days). Several morphological characteristics, such as germination rate, number of roots per seedling, length of primary root and cotyledon, and diameter of the stems were evaluated to assess the effects of chronic exposure. After 205days, BMAA bioaccumulation was quantified in roots, shoots, and mature seeds of T. aestivum. No adverse morphology effects were observed and no free intracellular BMAA was detected in any of the exposed plants. However, in mature seeds, protein-associated BMAA was detected at 217 +/- 150ng g FW-1; significantly more than in roots and shoots. This result demonstrates the unexpected bioaccumulation of a hydrophilic compound and highlights the demand to specify in addition to limit values for drinking water, tolerable daily intake rates for the cyanobacterial-neurotoxin BMAA.