A Chloroplastic UDP-Glucose Pyrophosphorylase from Arabidopsis Is the Committed Enzyme for the First Step of Sulfolipid Biosynthesis  

Abstract

Plants synthesize a sulfur-containing lipid, sulfoquinovosyldiacylglycerol, which is one of three nonphosphorus glycerolipids that provide the bulk of the structural lipids in photosynthetic membranes. Here, the identification of a novel gene, UDP-glucose pyrophosphorylase3 (UGP3), required for sulfolipid biosynthesis is described. Transcriptome coexpression analysis demonstrated highly correlated expression of UGP3 with known genes for sulfolipid biosynthesis in Arabidopsis thaliana. Liquid chromatography-mass spectrometry analysis of leaf lipids in two Arabidopsis ugp3 mutants revealed that no sulfolipid was accumulated in these mutants, indicating the participation of UGP3 in sulfolipid biosynthesis. From the deduced amino acid sequence, UGP3 was presumed to be a UDP-glucose pyrophosphorylase (UGPase) involved in the generation of UDP-glucose, serving as the precursor of the polar head of sulfolipid. Recombinant UGP3 was able to catalyze the formation of UDP-glucose from glucose-1-phosphate and UTP. A transient assay using fluorescence fusion proteins and UGPase activity in isolated chloroplasts indicated chloroplastic localization of UGP3. The transcription level of UGP3 was increased by phosphate starvation. A comparative genomics study on UGP3 homologs across different plant species suggested the structural and functional conservation of the proteins and, thus, a committing role for UGP3 in sulfolipid synthesis.

Lipidomic analysis of soybean leaves revealed tissue-dependent difference in lipid remodeling under phosphorus-limited growth conditions

“…Since the increase of free fatty acid is reported to be show the toxicity in yeast (Fakas et al 2011), accumulation of some TAG molecules under phosphorus limitation might be an adaptive response in plants to remove free fatty acids in some cellular spaces where this mechanism is required. In addition, it should be noted that accumulation of SQDG upon P limitation was not significantly induced here unlike in Arabidopsis and rice (Essigmann et al 1998;Okazaki et al 2009Okazaki et al , 2013Yu et al 2002).…”

“…The physiological importance of lipid remodeling in plants under P-deficient growth conditions has been investigated using several loss-of-function mutants, where genes involved in sulfoquinovosyldiacylglycerol (SQDG) biosynthesis (Essigmann et al 1998;Okazaki et al 2009;Yu et al 2002), induced accumulation of galactolipids (Awai et al 2001;Gaude et al 2008;Kelly and Dörmann 2002;Kobayashi et al 2006Kobayashi et al , 2009) and degradation of phospholipids under P-limited growth conditions (Cheng et al 2011;Cruz-Ramírez et al 2006;Gaude et al 2008;Nakamura et al 2005Nakamura et al , 2009) are disrupted. Some of them showed growth defects under P-limited conditions Okazaki et al 2013;Yu et al 2002).…”

Leaf Oil Body Functions as a Subcellular Factory for the Production of a Phytoalexin in Arabidopsis

“…To measure the 2-HOT contents by LC-MS, samples were prepared from the leaves as reported previously (Okazaki et al, 2009(Okazaki et al, , 2013, except that the samples were finally dissolved in ethanol. High-resolution electrospray MS was performed in negative ion mode using a Xevo G2 QTof mass spectrometer combined with an ACQUITY UPLC system (Waters).…”

The GreenCut2 Resource, a Phylogenomically Derived Inventory of Proteins Specific to the Plant Lineage

“…One member of this group, CrLPB1 (At3g56040), was originally identified as a protein important for the acclimation of Chlamydomonas to sulfur and phosphorus deprivation (79). The Arabidopsis ortholog of CrLPB1 was shown to be a UDP-glucose pyrophosphorylase, a chloroplast enzyme that is a component of the sulfolipid biosynthesis pathway (80). Sulfolipids are synthesized by photosynthetic organisms and are present in thylakoid membranes of plants, although they are not essential for cell growth.…”