JXB Advance Access originally published online on September 6, 2006
Journal of Experimental Botany 2006 57(14):3619-3626; doi:10.1093/jxb/erl110
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© 2006 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 |
The gene encoding the cytosolic small subunit of ADP-glucose pyrophosphorylase in barley endosperm also encodes the major plastidial small subunit in the leaves
1John Innes Centre, Norwich Research Park, Norfolk NR4 7UH, UK
2Norwegian University of Life Sciences, Department of Plant and Environmental Sciences, PO Box 5003, N-1432 Ås, Norway
3MATFORSK, Norwegian Food Research Institute, N-1430 Ås, Norway
* To whom correspondence should be addressed. E-mail: kay.denyer{at}bbsrc.ac.uk
The barley (Hordeum vulgare) gene Hv.AGP.S.1 produces two different transcripts encoding small subunits (SSUs) of ADP-glucose pyrophosphorylase (AGPase). It was shown previously that one of these transcripts, Hv.1a, encodes the cytosolic SSU in the endosperm. It is shown here that the other transcript produced from Hv.AGP.S.1, Hv.1b, encodes a plastidial SSU that is required for >90% of the AGPase activity in the leaves. Thus, both of the alternative transcripts encoded by Hv.AGP.S.1 are physiologically relevant: One is important for starch synthesis in the endosperm and the other for starch synthesis in the leaves. Although the Hv.1b transcript is abundant in embryos and present in endosperm, there is no evidence that a protein is produced from this transcript in these organs. This suggests that some, as yet unidentified, post-transcriptional control mechanism prevents the accumulation of the protein encoded by Hv.1b in embryos and endosperm but not in leaves. There is one other known gene in barley, Hv.AGP.S.2, encoding a SSU of AGPase. This gene has been shown to be responsible for the plastidial SSU in the endosperm. It is shown here that Hv.AGP.S.2 probably also makes some contribution to the SSU of AGPase in the leaves and may be responsible for most or all of the plastidial SSU in a range of non-photosynthetic plant organs including the embryo.
Key words: ADP-glucose pyrophosphorylase, barley, cereal, starch, transcriptional control
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