Abstract

Ascaulitoxin and its aglycone (2,4,7-triamino-5-hydroxyoctanoic acid, CAS 212268-55-8) are potentphytotoxins produced by Ascochyta caulina, a plant pathogen being developed for biocontrol of weeds.The mode of action of this non-protein amino acid was studied on Lemna paucicostata. Ascaulitoxin isa potent growth inhibitor, with an I50 for growth of less than 1 lM, almost completely inhibiting growthat about 3 lM. Its action is slow, starting with growth inhibition, followed by darker green fronds, andthen chlorosis and death. Most amino acids, including non-toxic non-protein amino acids, reversed theeffect of the toxin when supplemented in the same medium. Supplemental sucrose slightly increasedthe activity. D-Amino acids were equally good inhibitors of ascaulitoxin activity, indicating the amino acideffects may not be due to inhibition of amino acid synthesis. Oxaloacetate, the immediate precursor ofaspartate, also reversed the activity. LC-MS did not detect interaction of the compound with lysine, anamino acid that strongly reversed the effect of the phytotoxin. Metabolite profiling revealed that thetoxin caused distinct changes in amino acids. Reduction in alanine, paralleled by enhanced levels ofthe branched chain amino acids valine, leucine and isoleucine and nearly unchanged levels of pyruvate,might indicate that the conversion of pyruvate to alanine is affected by ascaulitoxin aglycone. In addition,reduced levels of glutamate/glutamine and aspartate/asparagine might suggest that synthesis andinterconversion reactions of these amino group donors are affected. However, neither alanine aminotransferasenor alanine: glyoxylate aminotransferase were inhibited by the toxin in vitro. Our observationsmight be explained by three hypotheses: (1) the toxin inhibits one or more aminotransferasesnot examined, (2) ascaulitoxin aglycone affects amino acid transporters, (3) ascaulitoxin aglycone is aprotoxin that is converted in vivo to an aminotransferase inhibitor.

Autore Pugliese

• Vurro Maurizio

Tutti gli autori

• Duke S.O.; Evidente A.; Fiore M.; Rimando A.M.; Dayan F.E.; Vurro M.; Christiansen N.; Looser R.; Hutzler J.; Grossmann K.

Titolo volume/Rivista

Pesticide biochemistry and physiology

Anno di pubblicazione

2011

ISSN

0048-3575

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

Ultimo Aggiornamento Citazioni

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Numero di citazioni Scopus

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Ultimo Aggiornamento Citazioni

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Settori ERC

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Codici ASJC

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