Journal Article

Amino acid pattern and glutamate metabolism during dehydration stress in the ‘resurrection’ plant <i>Sporobolus stapfianus</i>: a comparison between desiccation-sensitive and desiccation-tolerant leaves

Tommaso Martinelli, Anne Whittaker, Adriana Bochicchio, Concetta Vazzana, Akira Suzuki and Céline Masclaux-Daubresse

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 11, pages 3037-3046
Published in print August 2007 | ISSN: 0022-0957
Published online August 2007 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/erm161

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The present study analyses changes in nitrogen compounds, amino acid composition, and glutamate metabolism in the resurrection plant Sporobolus stapfianus during dehydration stress. Results showed that older leaves (OL) were desiccation-sensitive whereas younger leaves (YL) were desiccation-tolerant. OL lost their soluble protein more rapidly, and to a larger extent than YL. Enzymes of primary nitrogen assimilation were affected by desiccation and the decrease in the glutamine synthetase (GS, EC 6.3.1.2) and ferredoxin-dependent GOGAT (Fd-GOGAT, EC 1.4.7.1) activities was higher in OL than in YL, thus suggesting higher sensibility to dehydration. Moreover, YL showed higher total GS enzyme activity at the end of the dehydration stress and was shown to maintain high chloroplastic GS protein content during the entire stress period. Free amino acid content increased in both YL and OL between 88% and 6% relative water content. Interestingly, OL and YL did not accumulate the same amino acids. OL accumulated large amounts of proline and γ-aminobutyrate whereas YL preferentially accumulated asparagine and arginine. It is concluded (i) that modifications in the nitrogen and amino acid metabolism during dehydration stress were different depending on leaf development and (ii) that proline and γ-aminobutyrate accumulation in S. stapfianus leaves were not essential for the acquisition of desiccation tolerance. On the contrary, the accumulation of large amounts of asparagine and arginine in the YL during dehydration could be important and serve as essential nitrogen and carbon reservoirs useful during rehydration. In this context, the role of GS for asparagine accumulation in YL is discussed.

Keywords: Arginine; asparagine; GABA; glutamine synthetase; GOGAT; proline

Journal Article.  5654 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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