JXB Advance Access originally published online on March 1, 2007
Journal of Experimental Botany 2007 58(7):1571-1579; doi:10.1093/jxb/erm031
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
Adenosine 5'-phosphosulphate reductase is regulated differently in Allium cepa L. and Brassica oleracea L. upon exposure to H2S
1Laboratory of Plant Physiology, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
2Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK
3School of Forest and Ecosystems Sciences, The University of Melbourne, Water Street, Creswick, Victoria 3363, Australia
* To whom correspondence should be addressed. E-mail: mark.durenkamp{at}bbsrc.ac.uk
The reduction of adenosine 5'-phosphosulphate (APS) by APS reductase (APR) is considered to be one of the rate-limiting steps in the assimilation of sulphur in plants. In order to identify the mechanisms of regulation of this enzyme, the impact of atmospheric H2S exposure on mRNA expression, protein level, and activity of APR was studied in two species (Allium cepa L. and Brassica oleracea L.) with different physiological responses to H2S exposure. As expected, H2S exposure resulted in a rapid increase in thiol compounds in the shoot of both species. There was a substantial increase in total sulphur content in shoots of A. cepa, whereas it was hardly affected or even slightly decreased in B. oleracea. Sulphate uptake was only marginally affected in A. cepa, whereas it was strongly decreased in B. oleracea upon H2S exposure. Furthermore, H2S exposure resulted in a down-regulation of APR activity in shoot and roots of both species, which was probably mediated by a transcriptional mechanism of regulation by thiols, since mRNA levels also decreased. However, in contrast to B. oleracea, APR protein level was not affected by H2S exposure in A. cepa. The reduction in APR activity in onion was therefore achieved by an additional as yet unknown post-translational regulation. These results demonstrate that not only the physiological response to H2S, but also the molecular mechanisms of regulation of APR differ in the two species.
Key words: APS reductase, curly kale, hydrogen sulphide, onion, regulation, sulphate reduction, sulphate uptake, sulphur metabolism, thiols
Received 14 November 2006; Revised 30 January 2007 Accepted 31 January 2007