Natural toxins that affect plant amino acid metabolism

Authors: Duke, Stephen; Dayan, Franck

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 11/7/2013
Publication Date: 3/30/2015
Citation: Duke, S.O., Dayan, F.E. 2015. Natural toxins that affect plant amino acid metabolism. Book Chapter. In: Amino Acids in Higher Plants. J.P.F. D'Mello, Ed., CAB International, Wallingford, UK. p. 448-460.

Interpretive Summary: A diverse range of natural compounds interfere with the synthesis and other aspects of amino acid metabolism. Some are amino acid analogues, but most are not. This review covers a number of specific natural phytotoxic compounds by molecular target site. Inhibition of glutamine synthetase is of particular interest because a major herbicide is based on the microbial inhibitor of this enzyme, i.e., phosphinothricin. Natural inhibitors of plant glutamate, ornithine and methionine synthesis are also discussed. Glutamate is one of the most abundant and significant amino acids in living organisms. Ornithine is a key intermediate in the urea cycle and is a precursor of polyamines. Methionine is an essential amino acid for animals and humans, but its metabolism to cysteine and as a sulphur and methyl donor is of universal importance. In addition, the secondary effects of these inhibitors on various aspects of plant physiology are discussed. Finally, natural compounds that cause specific photodegradation of L-phenylalanine, that appear to interfere with amino acid transporters, and may cause toxicity at a L-phenylalanine binding site are mentioned.

Technical Abstract: A diverse range of natural compounds interfere with the synthesis and other aspects of amino acid metabolism. Some are amino acid analogues, but most are not. This review covers a number of specific natural phytotoxic compounds by molecular target site. Inhibition of glutamine synthetase is of particular interest because a major herbicide is based on the microbial inhibitor of this enzyme, i.e., phosphinothricin. Natural inhibitors of plant glutamate, ornithine and methionine synthesis are also discussed. Glutamate is one of the most abundant and significant amino acids in living organisms. Ornithine is a key intermediate in the urea cycle and is a precursor of polyamines. Methionine is an essential amino acid for animals and humans, but its metabolism to cysteine and as a sulphur and methyl donor is of universal importance. In addition, the secondary effects of these inhibitors on various aspects of plant physiology are discussed. Finally, natural compounds that cause specific photodegradation of L-phenylalanine, that appear to interfere with amino acid transporters, and may cause toxicity at a L-phenylalanine binding site are mentioned.