Plant Sphingolipids Today ‐ Are They Still Enigmatic?

Abstract

Sphingolipids are a diverse group of lipids found in all eukaryotes and some bacteria, consisting of a hydrophobic ceramide and a hydrophilic head group. We have summarised the contemporary understanding of the structure of plant sphingolipids with an emphasis on glucosylceramides and inositolphosphorylceramides. Plant glucosylceramides are important structural components of plasma and vacuole membranes. Inositolphosphorylceramides have been identified as moieties of the glycosylphosphorylinositol (GPI) anchors of plant proteins targeted to the plasma membrane. In the last few years, progress has been made in the cloning of plant genes coding for enzymes involved in sphingolipid metabolism. As found in yeast and mammals, the plant sphingolipid pathway is a potential generator of powerful cell signals. The role of plant sphingolipid metabolites in programmed cell death and calcium influx is discussed.

Involvement of sphingoid bases in mediating reactive oxygen intermediate production and programmed cell death in Arabidopsis

“…This might account for the cell death phenotype in a number of cases [16-19, 45, 46]. Ceramide synthase was proposed to be a multisubunit complex, of which members of the yeast longevity assurance gene (LAG1) family, including the tomato ASC1 gene [47], are the only components identified thus far [12,48]. Whereas the dominant ASC1 allele confers FB 1 -and AAL toxin-resistance to tomato [15,49], overexpression of the mammalian LAG1 homologs UOG1 [50], TRH1 and TRH4 [51] renders 293T cells resistant to FB 1 .…”

“…Thus, it appears that a decreased SPT activity, either by mutations or an enzymatic inhibitor of Because an impaired ceramide synthase causes PCD, the death signal(s) are likely the substrates of the enzyme. The currently known substrates of the enzyme include dh-sph and sph [10,12,13], which accumulate to substantially high levels upon treatment with FB 1 or AAL toxin in a variety of plant species [17,21,45] (see also Table 1) as well as several mammalian cell lines [14,52]. The observation that FB 1 causes massively increased sphingoid bases suggests that these compounds are key signal molecules that control plant PCD.…”

“…Sphingolipids are not only essential components of cellular membranes, but also act as second messengers to regulate stress responses, cell proliferation and apoptosis [10][11][12][13]. De novo biosynthesis of sphingolipids is initiated by the condensation of serine and palmitoylCoA to produce 3-ketosphinganine (3-KDS) [10,13].…”

Novel ceramides and a new glucoceramide from the roots of Incarvillea arguta

“…In the last few years, progress has been made in the cloning of plant genes coding for enzymes involved in sphingolipid metabolism. As found in yeast and mammals, the plant sphingolipid pathway is a potential generator of powerful cell signals (23). Ceramide, generated by the action of acid sphingomyelinase, has emerged as a biochemical mediator of stimuli as diverse as ionizing radiation, chemotherapy, heat, and reperfusion injury as well as infection with some pathogenic bacteria and viruses.…”

A new glucoceramide from the watermelon begonia, Pellionia repens

“…After removing solvent under reduced pressure, the residue (100 g) was partitioned between H 2 O and EtOAc to provide an ethyl acetate-soluble fraction (32 g), which was divided into eight fractions (Fr. [1][2][3][4][5][6][7][8] by gradient elution CC using CHCl 3 /MeOH (10:0-10:5, vol/vol). Fr.…”