Functional characterization of a higher plant sphingolipid Δ4-desaturase: Defining the role of sphingosine and sphingosine-1- phosphate in arabidopsis

Louise V. Michaelson, Simone Zäuner, Jonathan E. Markham, Richard P. Haslam, Radhika Desikan, Sarah Mugford, Sandra Albrecht, Dirk Warnecke, Petra Sperling, E. Heinz, Johnathan A. Napier

Research output: Contribution to journalArticle

81 Scopus citations

Abstract

The role of Δ4-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 Δ4-desaturase was achieved by heterologous expression in Pichia pastoris. A P. pastoris mutant disrupted in the endogenous sphingolipid Δ4-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 Δ4-unsaturated long-chain bases, confirming that this open reading frame encodes the sphingolipid Δ4-desaturase. At4g04930 has a very restricted expression pattern, transcripts only being detected in pollen and floral tissues. Arabidopsis insertion mutants disrupted in the sphingolipid Δ4-desaturase At4g04930 were isolated and found to be phenotypically normal. Sphingolipidomic profiling of a T-DNA insertion mutant indicated the absence of Δ4-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 Δ4-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 Δ4-unsaturated sphingolipids and their metabolites such as sphingosine-1-phosphate play a significant role in Arabidopsis growth and development. However, Δ4-unsaturated ceramides may play a previously unrecognized role in the channeling of substrates for the synthesis of glucosylceramides.

Original languageEnglish (US)
Pages (from-to)487-498
Number of pages12
JournalPlant physiology
Volume149
Issue number1
DOIs
StatePublished - Jan 2009

ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Plant Science

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    Michaelson, L. V., Zäuner, S., Markham, J. E., Haslam, R. P., Desikan, R., Mugford, S., Albrecht, S., Warnecke, D., Sperling, P., Heinz, E., & Napier, J. A. (2009). Functional characterization of a higher plant sphingolipid Δ4-desaturase: Defining the role of sphingosine and sphingosine-1- phosphate in arabidopsis. Plant physiology, 149(1), 487-498. https://doi.org/10.1104/pp.108.129411