Luttgeharm Kyle D, Kimberlin Athen N, Cahoon Rebecca E, Cerny Ronald L, Napier Johnathan A, Markham Jennifer E, Cahoon Edgar B
Center for Plant Science Innovation and Department of Biochemistry, E318 Beadle Center, 1901 Vine Street, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
Department of Chemistry, 710 Hamilton Hall, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
Phytochemistry. 2015 Jul;115:121-9. doi: 10.1016/j.phytochem.2015.02.019. Epub 2015 Mar 17.
Although sphingolipids are essential for male gametophytic development in Arabidopsis thaliana, sphingolipid composition and biosynthetic gene expression have not been previously examined in pollen. In this report, electrospray ionization (ESI)-MS/MS was applied to characterization of sphingolipid compositional profiles in pollen isolated from wild type Arabidopsis Col-0 and a long-chain base (LCB) Δ4 desaturase mutant. Pollen fractions were highly enriched in glucosylceramides (GlcCer) relative to levels previously reported in leaves. Accompanying the loss of the Δ4 unsaturated LCB sphingadiene (d18:2) in the Δ4 desaturase mutant was a 50% reduction in GlcCer concentrations. In addition, pollen glycosylinositolphosphoceramides (GIPCs) were found to have a complex array of N-acetyl-glycosylated GIPCs, including species with up to three pentose units that were absent from leaf GIPCs. Underlying the distinct sphingolipid composition of pollen, genes for key biosynthetic enzymes for GlcCer and d18:2 synthesis and metabolism were more highly expressed in pollen than in leaves or seedlings, including genes for GlcCer synthase (GCS), sphingoid base C-4 hydroxylase 2 (SBH2), LCB Δ8 desaturases (SLD1 and SLD2), and LOH2 ceramide synthase (LOH2). Overall, these findings indicate strikingly divergent sphingolipid metabolism between pollen and leaves in Arabidopsis, the significance of which remains to be determined.
虽然鞘脂对于拟南芥雄配子体发育至关重要，但此前尚未对花粉中的鞘脂组成和生物合成基因表达进行研究。在本报告中，采用电喷雾电离（ESI）-串联质谱（MS/MS）对从野生型拟南芥Col-0和一个长链碱基（LCB）Δ4去饱和酶突变体中分离出的花粉鞘脂组成谱进行表征。相对于此前在叶片中报道的水平，花粉组分中富含葡萄糖神经酰胺（GlcCer）。伴随Δ4去饱和酶突变体中Δ4不饱和LCB鞘氨二烯（d18:2）的缺失，GlcCer浓度降低了50%。此外，发现花粉糖基肌醇磷酸神经酰胺（GIPC）具有一系列复杂的N-乙酰糖基化GIPC，包括含有多达三个戊糖单元的种类，而这些种类在叶片GIPC中不存在。花粉独特的鞘脂组成背后，参与GlcCer和d18:2合成与代谢的关键生物合成酶基因在花粉中的表达高于叶片或幼苗，包括葡萄糖神经酰胺合酶（GCS）、鞘氨醇碱基C-4羟化酶2（SBH2）、LCB Δ8去饱和酶（SLD1和SLD2）以及LOH2神经酰胺合酶（LOH2）的基因。总体而言，这些发现表明拟南芥花粉和叶片之间的鞘脂代谢存在显著差异，其意义尚待确定。
