Arabidopsis sphingosine kinase and the effects of phytosphingosine-1-phosphate on stomatal aperture

• Published in: Plant physiology (Bethesda) Vol. 137; no. 2; pp. 724 - 737
• Main Authors: Coursol, S, Le Stunff, H, Lynch, D.V, Gilroy, S, Assmann, S.M, Spiegel, S
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.02.2005; American Society of Plant Physiologists; Oxford University Press ; American Society of Plant Biologists
• Subjects: Agronomy. Soil science and plant productions; Animal social behavior; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis thaliana; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; Cell membranes; Economic plant physiology; enzyme activity; enzyme kinetics; Enzymes; Fundamental and applied biological sciences. Psychology; Genetics; Guard cells; kinases; Kinetics; Leaves; Life Sciences; Lipids; Micelles; Molecular Structure; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Phylogeny; phytosphingosine-1-phosphate; Plant Leaves - enzymology; plant proteins; Plants genetics; Sphingolipids; Sphingosine - analogs & derivatives; Sphingosine - chemistry; Sphingosine - physiology; sphingosine kinase; stomata; Substrate Specificity; Water relations, transpiration, stomata; Turgor; Enzyme; Transferases; Long chain; Sphingolipid; Lipids; Stomata; Plant leaf; Phylogeny; Guard cell; Arabidopsis thaliana; Gene; Cruciferae; Kinase; Dicotyledones; Angiospermae; Abscisic acid; Spermatophyta; Kinetics; Mutation; G protein; Non-programmatic; PHYTOSPHINGOSINE-1-PHOSPHATE; OUVERTURE
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.055806

Sphingolipids are a major component of membrane lipids and their metabolite sphingosine-1-phosphate (S1P) is a potent lipid mediator in animal cells. Recently, we have shown that the enzyme responsible for S1P production, sphingosine kinase (SphK), is stimulated by the phytohormone abscisic acid in guard cells of Arabidopsis (Arabidopsis thaliana) and that S1P is effective in regulating guard cell turgor. We have now characterized SphK from Arabidopsis leaves. SphK activity was mainly associated with the membrane fraction and phosphorylated predominantly the [Delta]4-unsaturated long-chain sphingoid bases sphingosine (Sph) and 4,8-sphingadienine, and to a lesser extent, the saturated long-chain sphingoid bases dihydrosphingosine and phytosphingosine (Phyto-Sph). 4-Hydroxy-8-sphingenine, which is a major sphingoid base in complex glycosphingolipids from Arabidopsis leaves, was a relatively poor substrate compared with the corresponding saturated Phyto-Sph. In contrast, mammalian SphK1 efficiently phosphorylated Sph, dihydrosphingosine, and 4,8-sphingadienine, but not the 4-hydroxylated long-chain bases Phyto-Sph and 4-hydroxy-8-sphingenine. Surface dilution kinetic analysis of Arabidopsis SphK with Sph presented in mixed Triton X-100 micelles indicated that SphK associates with the micellar surface and then with the substrate presented on the surface. In addition, measurements of SphK activity under different assay conditions combined with phylogenetic analysis suggest that multiple isoforms of SphK may be expressed in Arabidopsis. Importantly, we found that phytosphingosine-1-phosphate, similar to S1P, regulates stomatal apertures and that its action is impaired in guard cells of Arabidopsis plants harboring T-DNA null mutations in the sole prototypical G-protein [alpha]-subunit gene, GPA1.