Ornithine-δ-aminotransferase is essential for Arginine Catabolism but not for Proline BiosynthesisReport as inadecuate

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BMC Plant Biology

, 8:40

First Online: 17 April 2008Received: 11 December 2007Accepted: 17 April 2008


BackgroundLike many other plant species, Arabidopsis uses arginine Arg as a storage and transport form of nitrogen, and proline Pro as a compatible solute in the defence against abiotic stresses causing water deprivation. Arg catabolism produces ornithine Orn inside mitochondria, which was discussed controversially as a precursor for Pro biosynthesis, alternative to glutamate Glu.

ResultsWe show here that ornithine-δ-aminotransferase δOAT, At5g46180, the enzyme converting Orn to pyrroline-5-carboxylate P5C, is localised in mitochondria and is essential for Arg catabolism. Wildtype plants could readily catabolise supplied Arg and Orn and were able to use these amino acids as the only nitrogen source. Deletion mutants of δOAT, however, accumulated urea cycle intermediates when fed with Arg or Orn and were not able to utilize nitrogen provided as Arg or Orn. Utilisation of urea and stress induced Pro accumulation were not affected in T-DNA insertion mutants with a complete loss of δOAT expression.

ConclusionOur findings indicate that δOAT feeds P5C exclusively into the catabolic branch of Pro metabolism, which yields Glu as an end product. Conversion of Orn to Glu is an essential route for recovery of nitrogen stored or transported as Arg. Pro biosynthesis occurs predominantly or exclusively via the Glu pathway in Arabidopsis and does not depend on Glu produced by Arg and Orn catabolism.


ASLargininosuccinate lyase

ASSYargininosuccinate synthetase


Dwdry weight

Fwfresh weight






OTCornithine transcarbamylase


P5CDHP5C dehydrogenase

P5CRP5C reductase

P5CSP5C synthetase


ProDHPro dehydrogenase.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2229-8-40 contains supplementary material, which is available to authorized users.

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Author: Dietmar Funck - Bettina Stadelhofer - Wolfgang Koch

Source: https://link.springer.com/

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