Sphingolipids in the Root Play an Important Role in Regulating the Leaf Ionome inArabidopsis thaliana   

Abstract

Sphingolipid synthesis is initiated by condensation of Ser with palmitoyl-CoA producing 3-ketodihydrosphinganine (3-KDS), which is reduced by a 3-KDS reductase to dihydrosphinganine. Ser palmitoyltransferase is essential for plant viability. Arabidopsis thaliana contains two genes (At3g06060/TSC10A and At5g19200/TSC10B) encoding proteins with significant similarity to the yeast 3-KDS reductase, Tsc10p. Heterologous expression in yeast of either Arabidopsis gene restored 3-KDS reductase activity to the yeast tsc10Δ mutant, confirming both as bona fide 3-KDS reductase genes. Consistent with sphingolipids having essential functions in plants, double mutant progeny lacking both genes were not recovered from crosses of single tsc10A and tsc10B mutants. Although the 3-KDS reductase genes are functionally redundant and ubiquitously expressed in Arabidopsis, 3-KDS reductase activity was reduced to 10% of wild-type levels in the loss-of-function tsc10a mutant, leading to an altered sphingolipid profile. This perturbation of sphingolipid biosynthesis in the Arabidopsis tsc10a mutant leads an altered leaf ionome, including increases in Na, K, and Rb and decreases in Mg, Ca, Fe, and Mo. Reciprocal grafting revealed that these changes in the leaf ionome are driven by the root and are associated with increases in root suberin and alterations in Fe homeostasis.

Arabidopsis 3-Ketoacyl-Coenzyme A Synthase9 Is Involved in the Synthesis of Tetracosanoic Acids as Precursors of Cuticular Waxes, Suberins, Sphingolipids, and Phospholipids

“…However, no KCS involved in VLCFA elongation for sphingolipid synthesis has been reported yet. The LCB1, SBH1 and SBH2, and TSC10A and TSC10B genes encoding the LCB1 subunit of Ser palmitoyltransferase, sphingolipid base hydroxylase1 and sphingolipid base hydroxylase2, and proteins similar to the yeast 3-KDS reductase, which are involved in the sphingolipid biosynthetic pathway, respectively, have been shown to be expressed in whole plants (Chen et al, 2006(Chen et al, , 2008Chao et al, 2011), suggesting that the Arabidopsis KCSs expressed ubiquitously in various organs and tissues may be involved in VLCFA elongation, which is used for sphingolipid biosynthesis. In this study, we found that ubiquitously expressed KCS9 is involved in the elongation of C22 to C24 VLCFAs, which is required for sphingolipid synthesis.…”

Altered Lipid Composition and Enhanced Nutritional Value of Arabidopsis Leaves following Introduction of an Algal Diacylglycerol Acyltransferase 2

“…They are known to play roles in membrane structure, signal transduction, and programmed cell death (Chen et al, 2009). GlcCer and GIPC lipids are the two major classes of sphingolipids in plants (Chen et al, 2008;Li-Beisson et al, 2010;Chao et al, 2011). In Arabidopsis, the cutin polymer is comprised of DCAs, v-hydroxy FAs, and glycerol monomers, which are embedded with and covered by waxes (Bonaventure et al, 2004;Franke et al, 2005).…”

Identification of a Sphingolipid α-Glucuronosyltransferase That Is Essential for Pollen Function inArabidopsis

“…Identification of genes encoding sphingolipid biosynthetic proteins has implicated sphingolipids in many important processes including ion transport (Chao et al, 2011), endomembrane trafficking (Markham et al, 2011), programmed cell death (Liang et al, 2003), cold tolerance (Chen et al, 2012), stomatal closure (Coursol et al, 2005), and pollen development (Chen et al, 2006). However, little information is available about the roles of sphingolipid glycosylation.…”

“…Mutations in genes encoding subunits of serine palmitoyltransferase are pollen lethal, indicating that sphingolipids are essential in plants (Chen et al, 2006;Kimberlin et al, 2013). 3-Ketosphinganine reductase then converts 3-ketosphinganine to sphinganine (Chao et al, 2011), which can be modified by hydroxylation and unsaturation to create up to nine different LCBs with variations in structure. Free LCBs can be converted to ceramide by ceramide synthases, also known as Lag 1 Homolog (LOH) enzymes, which acylate LCBs with fatty acids.…”