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Title: Probing sphingolipid function in plants by the analysis of Arabidopsis mutants with altered sphingolipid content and composition

Author
item DIETRICH, CHARLES
item CAHOON, EDGAR
item CHEN, MING - D DANFORTH PLT SCI CTR

Submitted to: International Symposium on Plant Lipids
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2006
Publication Date: 7/17/2006
Citation: Dietrich, C.R., Cahoon, E.B., Chen, M. 2006. Probing sphingolipid function in plants by the analysis of Arabidopsis mutants with altered sphingolipid content and composition [abstract]. 17th International Symposium on Plant Lipids.

Interpretive Summary:

Technical Abstract: Sphingolipids are major components of the plasma membrane and tonoplasts of plant cells. These lipids are enriched in detergent-resistant membrane fractions or lipid-rafts prepared from plasma membrane and have been linked to signaling pathways in plants. Serine palmitoyltransferase (SPT), which catalyzes the initial step in sphingolipid long-chain base (LCB) synthesis, was targeted to determine the consequences of reduced flux into sphingolipid biosynthesis. As part of this research, we determined through yeast complementation that the Arabidopsis SPT is a heteromeric enzyme that is composed of LCB1 and LCB2 subunits. Complete knockout of the one LCB1 gene or the two LCB2 genes resulted in lethality, which demonstrated that sphingolipids are essential for the viability of Arabidopsis. Partial down-regulation of sphingolipid synthesis by RNAi suppression of LCB1 was accompanied by substantial reductions in growth, due primarily to decreased cell expansion, but surprisingly this did not affect the total content of LCBs on a weight basis. This suggests that plants adjust cell expansion to compensate for the availability of sphingolipids. To examine the effect of more subtle alterations in sphingolipid content, mutants with complete loss of the LCB selta4-hydroxlase were prepared. These mutants, which lacked tri-hydroxy LCBs, were severely dwarfed and displayed a seedling lethal phenotype. Overall, these results demonstrate that sphingolipids are essential in plants and relatively small changes in their composition can have profound effects on growth and development.