Journal Article

Maize nitrilases have a dual role in auxin homeostasis and β-cyanoalanine hydrolysis

Verena Kriechbaumer, Woong June Park, Markus Piotrowski, Robert B. Meeley, Alfons Gierl and Erich Glawischnig

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 15-16, pages 4225-4233
Published in print December 2007 | ISSN: 0022-0957
Published online December 2007 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/erm279

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The auxin indole-3-acetic acid (IAA), which is essential for plant growth and development, is suggested to be synthesized via several redundant pathways. In maize (Zea mays), the nitrilase ZmNIT2 is expressed in auxin-synthesizing tissues and efficiently hydrolyses indole-3-acetonitrile to IAA. Zmnit2 transposon insertion mutants were compromised in root growth in young seedlings and sensitivity to indole-3-acetonitrile, and accumulated lower quantities of IAA conjugates in kernels and root tips, suggesting a substantial contribution of ZmNIT2 to total IAA biosynthesis in maize. An additional enzymatic function, turnover of β-cyanoalanine, is acquired when ZmNIT2 forms heteromers with the homologue ZmNIT1. In plants carrying an insertion mutation in either nitrilase gene this activity was strongly reduced. A dual role for ZmNIT2 in auxin biosynthesis and in cyanide detoxification as a heteromer with ZmNIT1 is therefore proposed.

Keywords: Auxin; cyanoalanine; IAA; IAN; maize; nitrilase

Journal Article.  4974 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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