A global LC-MS2 -based methodology to identify and quantify anionic phospholipids in plant samples

peer reviewedAnionic phospholipids (PS, PA, PI, PIPs) are low-abundant phospholipids with impactful functions in cell signaling, membrane trafficking and cell differentiation processes. They can be quickly metabolized and can transiently accumulate at defined spots within the cell or an organ to respond to physiological or environmental stimuli. As even a small change in their composition profile will produce a significant effect on biological processes, it is crucial to develop a sensitive and optimized analytical method to accurately detect and quantify them. While thin-layer chromatography (TLC) separation coupled with gas chromatography (GC) detection methods already exist, they do not allow for precise, sensitive, and accurate quantification of all anionic phospholipid species. Here we developed a method based on high-performance liquid chromatography (HPLC) combined with two-dimensional mass spectrometry (MS 2) by MRM mode to detect and quantify all molecular species and classes of anionic phospholipids in one shot. This method is based on a derivatization step by methylation that greatly enhances the ionization, the separation of each peak, the peak resolution as well as the limit of detection and quantification for each individual molecular species, and more particularly for PA and PS. Our method universally works in various plant samples. Remarkably, we identified that PS is enriched with very long chain fatty acids in the roots but not in aerial organs of Arabidopsis thaliana. Our work thus paves the way for new studies on how the composition of anionic lipids is finely tuned during plant development and environmental responses

High lipid order of Arabidopsis cell‐plate membranes mediated by sterol and DYNAMIN‐RELATED PROTEIN1A function

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109568/1/tpj12674.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109568/2/tpj12674-sup-0002-FigS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109568/3/tpj12674-sup-0001-FigS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109568/4/tpj12674-sup-0003-FigS3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109568/5/tpj12674-sup-0004-FigS4.pd

Endocytosis restricts Arabidopsis KNOLLE syntaxin to the cell division plane during late cytokinesis

Cytokinesis represents the final stage of eukaryotic cell division during which the cytoplasm becomes partitioned between daughter cells. The process differs to some extent between animal and plant cells, but proteins of the syntaxin family mediate membrane fusion in the plane of cell division in diverse organisms. How syntaxin localization is kept in check remains elusive. Here, we report that localization of the Arabidopsis KNOLLE syntaxin in the plane of cell division is maintained by sterol-dependent endocytosis involving a clathrin- and DYNAMIN-RELATED PROTEIN1A-dependent mechanism. On genetic or pharmacological interference with endocytosis, KNOLLE mis-localizes to lateral plasma membranes after cell-plate fusion. Fluorescence-loss-in-photo-bleaching and fluorescence-recovery-after-photo-bleaching experiments reveal lateral diffusion of GFP-KNOLLE from the plane of division to lateral membranes. In an endocytosis-defective sterol biosynthesis mutant displaying lateral KNOLLE diffusion, KNOLLE secretory trafficking remains unaffected. Thus, restriction of lateral diffusion by endocytosis may serve to maintain specificity of syntaxin localization during late cytokinesis

PUCHI regulates very long chain fatty acid biosynthesis during lateral root and callus formation

© 2019 National Academy of Sciences. All rights reserved. Lateral root organogenesis plays an essential role in elaborating plant root system architecture. In Arabidopsis, the AP2 family transcription factor PUCHI controls cell proliferation in lateral root primordia. To identify potential targets of PUCHI, we analyzed a time course transcriptomic dataset of lateral root formation. We report that multiple genes coding for very long chain fatty acid (VLCFA) biosynthesis enzymes are induced during lateral root development in a PUCHI-dependent manner. Significantly, several mutants perturbed in VLCFA biosynthesis show similar lateral root developmental defects as puchi-1. Moreover, puchi-1 roots display the same disorganized callus formation phenotype as VLCFA biosynthesis-deficient mutants when grown on auxin-rich callus-inducing medium. Lipidomic profiling of puchi-1 roots revealed reduced VLCFA content compared with WT. We conclude that PUCHI-regulated VLCFA biosynthesis is part of a pathway controlling cell proliferation during lateral root and callus formation

Choline transporter CTL1 locates at the <i>trans</i>-Golgi network (TGN), a post-Golgi compartment acting as a central hub in the cell where endosomal plasma membrane recycling takes place as well as secretory sorting to plasma membrane and trafficking to late endosomes.

<p>CTL1 is involved in phosphatidylcholine (PC) membrane homeostasis, probably by creating a gradient of choline on either side of TGN membranes. Two studies published in this issue of <i>PLOS Biology</i> show that TGN sorting of plasmodesmata callose-binding proteins (PDCBs), the ion transporter NRAMP1, and the auxin carrier PIN1, which polarly localised at the basal plasma membrane, depends on choline-mediated lipid homeostasis. Abbreviations: PA, phosphatidic acid.</p

Metabolic Cellular Communications: Feedback Mechanisms between Membrane Lipid Homeostasis and Plant Development

International audienceMembrane lipids are often viewed as passive building blocks of the endomembrane system. However, mounting evidence suggests that sphingolipids, sterols, and phospholipids are specifically targeted by developmental pathways, notably hormones, in a cell- or tissue-specific manner to regulate plant growth and development. Targeted modifications of lipid homeostasis may act as a way to execute a defined developmental program, for example, by regulating other signaling pathways or participating in cell differentiation. Furthermore, these regulations often feed back on the very signaling pathway that initiates the lipid metabolic changes. Here, we review several recent examples highlighting the intricate feedbacks between membrane lipid homeostasis and plant development. In particular, these examples illustrate how all aspects of membrane lipid metabolic pathways are targeted by these feedback regulations. We propose that the time has come to consider membrane lipids and lipid metabolism as an integral part of the developmental program needed to build a plant

AP2/ERF transcription factors orchestrate very long chain fatty acid biosynthesis during Arabidopsis lateral root development

International audienc

Ethylene Regulates Differential Growth via BIG ARF-GEF-Dependent Post-Golgi Secretory Trafficking in Arabidopsis

International audienc

Sphingolipids in plants: a guidebook on their function in membrane architecture, cellular processes, and environmental or developmental responses

National audienceSphingolipids are fundamental lipids involved in various cellular, developmental and stress-response processes. As such, they orchestrate not only vital molecular mechanisms of living cells but also act in diseases, thus qualifying as potential pharmaceutical targets. Sphingolipids are universal to eukaryotes and are also present in some prokaryotes. Some sphingolipid structures are conserved between animals, plants and fungi, whereas others are found only in plants and fungi. In plants, the structural diversity of sphingolipids, as well as their downstream effectors and molecular and cellular mechanisms of action, are of tremendous interest to both basic and applied researchers, as about half of all small molecules in clinical use originate from plants. Here, we review recent advances towards a better understanding of the biosynthesis of sphingolipids, the diversity in their structures as well as their functional roles in membrane architecture, cellular processes such as membrane trafficking and cell polarity, and cell responses to environmental or developmental signals