Changes in free amino acid concentration in rye grain in response to nitrogen and sulphur availability, and expression analysis of genes involved in asparagine metabolism

A - Papers appearing in refereed journals

Postles, J., Curtis, T. Y., Powers, S. J., Elmore, J. S., Mottram, D. S. and Halford, N. G. 2016. Changes in free amino acid concentration in rye grain in response to nitrogen and sulphur availability, and expression analysis of genes involved in asparagine metabolism. Frontiers in Plant Science. 7, p. 917.

AuthorsPostles, J., Curtis, T. Y., Powers, S. J., Elmore, J. S., Mottram, D. S. and Halford, N. G.
Abstract

Free asparagine plays a central role in nitrogen storage and transport in many plant species due to its relatively high ratio of nitrogen to carbon. However, it is also a precursor for acrylamide, a Class 2a carcinogen that forms during high-temperature processing and cooking. The concentration of free asparagine was shown to increase by approximately 70% in rye grain in response to severe sulfur deficiency (F-test, p = 0.004), while the concentration of both free asparagine and free glutamine increased (by almost threefold and approximately 62%, respectively) in response to nitrogen application (F-test, p < 0.001 for free asparagine; p = 0.004 for free glutamine). There were also effects of nutrient supply on other free amino acids: The concentration of free proline, for example, showed a significant (F-test, p = 0.019) effect of nitrogen interacting with sulfur, with the highest concentration occurring when the plants were deprived of both nitrogen and sulfur. Polymerase chain reaction products for several genes involved in asparagine metabolism and its regulation were amplified from rye grain cDNA. These genes were asparagine synthetase-1 (ScASN1), glutamine synthetase-1 (ScGS1), potassium-dependent asparaginase (ScASP), aspartate kinase (ScASK), and general control non-derepressible-2 (ScGCN2). The expression of these genes and of a previously described sucrose non-fermenting-1-related protein kinase-1 gene (ScSnRK1) was analyzed in flag leaf and developing grain in response to nitrogen and sulfur supply, revealing a significant (F-test, p < 0.05) effect of nitrogen supply on ScGS1 expression in the grain at 21 days post-anthesis. There was also evidence of an effect of sulfur deficiency on ScASN1 gene expression. However, although this effect was large (almost 10-fold) it was only marginally statistically significant (F-test, 0.05 < p < 0.10). The study reinforced the conclusion that nutrient availability can have a profound impact on the concentrations of different free amino acids, something that is often overlooked by plant physiologists but which has important implications for flavor, color, and aroma development during cooking and processing, as well as the production of undesirable contaminants such as acrylamide.

Year of Publication2016
JournalFrontiers in Plant Science
Journal citation7, p. 917
Digital Object Identifier (DOI)doi:10.3389/fpls.2016.00917
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeWheat
BBSRC LINK: Genetic improvement of wheat to reduce the potential for acrylamide formation during processing
BBSRC CASE studentship: Agronomic and genetic approaches to reducing the acrylamide potential of rye
[20:20 Wheat] Maximising yield potential of wheat
Statistics Department (Rothamsted)
Publisher's version
Copyright license
CC BY
Output statusPublished
Publication dates
Online22 Jun 2016
Publication process dates
Accepted09 Jun 2016
PublisherFrontiers Media SA
ISSN1664-462X

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