First published online October 31, 2008; 10.1104/pp.108.129411
Plant Physiology 149:487-498 (2009)
© 2009 American Society of Plant Biologists
OPEN ACCESS ARTICLE
BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES
Functional Characterization of a Higher Plant Sphingolipid  4-Desaturase: Defining the Role of Sphingosine and Sphingosine-1-Phosphate in Arabidopsis1,[W],[OA]
Louise V. Michaelson,
Simone Zäuner,
Jonathan E. Markham,
Richard P. Haslam,
Radhika Desikan,
Sarah Mugford2,
Sandra Albrecht3,
Dirk Warnecke,
Petra Sperling4,
E. Heinz and
Johnathan A. Napier*
Biological Chemistry Department, Rothamsted Research, Harpenden, Hertshire AL5 2JQ, United Kingdom (L.V.M., R.P.H., S.M., J.A.N.); Biocenter Klein Flottbek, University of Hamburg, D–22609 Hamburg, Germany (S.Z., S.A., D.W., P.S., E.H.); Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (J.E.M.); and Division of Biology, Imperial College London, London SW7 2AZ, United Kingdom (R.D.)
The role of  4-unsaturated sphingolipid long-chain bases such as sphingosine was investigated in Arabidopsis (Arabidopsis thaliana). Identification and functional characterization of the sole Arabidopsis ortholog of the sphingolipid 4-desaturase was achieved by heterologous expression in Pichia pastoris. A P. pastoris mutant disrupted in the endogenous sphingolipid 4-desaturase gene was unable to synthesize glucosylceramides. Synthesis of glucosylceramides was restored by the expression of Arabidopsis gene At4g04930, and these sphingolipids were shown to contain 4-unsaturated long-chain bases, confirming that this open reading frame encodes the sphingolipid 4-desaturase. At4g04930 has a very restricted expression pattern, transcripts only being detected in pollen and floral tissues. Arabidopsis insertion mutants disrupted in the sphingolipid 4-desaturase At4g04930 were isolated and found to be phenotypically normal. Sphingolipidomic profiling of a T-DNA insertion mutant indicated the absence of 4-unsaturated sphingolipids in floral tissue, also resulting in the reduced accumulation of glucosylceramides. No difference in the response to drought or water loss was observed between wild-type plants and insertion mutants disrupted in the sphingolipid 4-desaturase At4g04930, nor was any difference observed in stomatal closure after treatment with abscisic acid. No differences in pollen viability between wild-type plants and insertion mutants were detected. Based on these observations, it seems unlikely that 4-unsaturated sphingolipids and their metabolites such as sphingosine-1-phosphate play a significant role in Arabidopsis growth and development. However, 4-unsaturated ceramides may play a previously unrecognized role in the channeling of substrates for the synthesis of glucosylceramides.
1 This work was supported by the Deutsche Forschungsgemeinschaft (grant no. SP 967/1–1 to P.S. and S.Z.) and the Biotechnology and Biological Sciences Research Council (to Rothamsted Research).
2 Present address: John Innes Centre, Norwich NR4 7UH, United Kingdom.
3 Present address: Research Center Borstel, Parkallee 1–40, 23845 Borstel, Germany.
4 Deceased.
The authors responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) are: Dirk Warnecke (warnecke{at}botanik.uni-hamburg.de) and Johnathan A. Napier (johnathan.napier{at}bbsrc.ac.uk).
[W] The online version of this article contains Web-only data.
[OA] Open Access articles can be viewed online without a subscription.
www.plantphysiol.org/cgi/doi/10.1104/pp.108.129411
* Corresponding author; e-mail johnathan.napier{at}bbsrc.ac.uk.
Received September 6, 2008;
accepted October 17, 2008;
published October 31, 2008.
This article has been cited by other articles:
|
|
|
|
 
S. M. Brady and N. J. Provart
Web-Queryable Large-Scale Data Sets for Hypothesis Generation in Plant Biology
PLANT CELL,
April 1, 2009;
21(4):
1034 - 1051.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
