AtCSLD2 is an integral Golgi membrane protein with its N-terminus facing the cytosol (original) (raw)
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Nature Communications, 2016
As the most abundant biopolymer on Earth, cellulose is a key structural component of the plant cell wall. Cellulose is produced at the plasma membrane by cellulose synthase (CesA) complexes (CSCs), which are assembled in the endomembrane system and trafficked to the plasma membrane. While several proteins that affect CesA activity have been identified, components that regulate CSC assembly and trafficking remain unknown. Here we show that STELLO1 and 2 are Golgi-localized proteins that can interact with CesAs and control cellulose quantity. In the absence of STELLO function, the spatial distribution within the Golgi, secretion and activity of the CSCs are impaired indicating a central role of the STELLO proteins in CSC assembly. Point mutations in the predicted catalytic domains of the STELLO proteins indicate that they are glycosyltransferases facing the Golgi lumen. Hence, we have uncovered proteins that regulate CSC assembly in the plant Golgi apparatus.
The trafficking of the cellulose synthase complex in higher plants
Annals of Botany, 2014
† Background Cellulose is an important constituent of plant cell walls in a biological context, and is also a material commonly utilized by mankind in the pulp and paper, timber, textile and biofuel industries. The biosynthesis of cellulose in higher plants is a function of the cellulose synthase complex (CSC). The CSC, a large transmembrane complex containing multiple cellulose synthase proteins, is believed to be assembled in the Golgi apparatus, but is thought only to synthesize cellulose when it is localized at the plasma membrane, where CSCs synthesize and extrude cellulose directly into the plant cell wall. Therefore, the delivery and endocytosis of CSCs to and from the plasma membrane are important aspects for the regulation of cellulose biosynthesis. † Scope Recent progress in the visualization of CSC dynamics in living plant cells has begun to reveal some of the routes and factors involved in CSC trafficking. This review highlights the most recent major findings related to CSC trafficking, provides novel perspectives on how CSC trafficking can influence the cell wall, and proposes potential avenues for future exploration.
Plant Cell, 2009
Plant growth and organ formation depend on the oriented deposition of load-bearing cellulose microfibrils in the cell wall. Cellulose is synthesized by plasma membrane-bound complexes containing cellulose synthase proteins (CESAs). Here, we establish a role for the cytoskeleton in intracellular trafficking of cellulose synthase complexes (CSCs) through the in vivo study of the green fluorescent protein (GFP)-CESA3 fusion protein in Arabidopsis thaliana hypocotyls. GFP-CESA3 localizes to the plasma membrane, Golgi apparatus, a compartment identified by the VHA-a1 marker, and, surprisingly, a novel microtubule-associated cellulose synthase compartment (MASC) whose formation and movement depend on the dynamic cortical microtubule array. Osmotic stress or treatment with the cellulose synthesis inhibitor CGA 325'615 induces internalization of CSCs in MASCs, mimicking the intracellular distribution of CSCs in nongrowing cells. Our results indicate that cellulose synthesis is coordinated with growth status and regulated in part through CSC internalization. We find that CSC insertion in the plasma membrane is regulated by pauses of the Golgi apparatus along cortical microtubules. Our data support a model in which cortical microtubules not only guide the trajectories of CSCs in the plasma membrane, but also regulate the insertion and internalization of CSCs, thus allowing dynamic remodeling of CSC secretion during cell expansion and differentiation.
Trafficking of the Plant Cellulose Synthase Complex
PLANT PHYSIOLOGY, 2010
Cellulose is the most abundant component of plant cell walls and its importance is well documented. In the primary cell wall it forms part of the load-bearing network that both controls and maintains cell shape, while allowing regulated cell expansion that is essential during growth. Cellulose is also the major component of secondary cell walls where it is required for mechanical strength for the plant (for review, see .
The Plant Cell, 2019
(N.C.C.). IN A NUTSHELL 40 41 Background: Grasses and other commelinid species possess a distinct type of primary cell wall 42 from all other angiosperms based on the structures and relative proportions of their pectic and hemicellulosic polysaccharides, and the presence or absence of a phenylpropanoid network. The plant ER-Golgi apparatus is the site of synthesis, packaging and export of all non-cellulosic polysaccharides and proteins of the cell wall. Questions: What polysaccharide structures are present in the Golgi compared to those in the cell wall, and how do they differ between two species representative of the two distinct types of cell wall? What is the maize Golgi proteome that supports synthesis of cell wall polysaccharides unique to grasses? Findings: We established that a large proportion of carbohydrate consisting of mostly the glycan moieties of arabinogalactan-proteins are common to the Golgi of maize (Zea mays) and Arabidopsis, Pectic and hemicellulosic polysaccharides that accumulated in Arabidopsis and maize Golgi do not reflect the relative proportions that accumulate in their respective cell walls. Flotation centrifugation followed by free-flow electrophoresis provided the richest collection to date of maize Golgi membrane proteins associated with the synthesis and metabolism of the cell wall. However, this full complement of Golgi cell-wall polysaccharides, and the synthases and glycosyl transferases that make them, represent compositions distinct from those of their cell wall types. Next steps: The glycome composition of the Golgi represents a snapshot of what is made and accumulated at the time of harvest. A flux analysis is needed to determine relative rates of synthesis and export of Golgi polysaccharides to account for the anomalous accumulation of cell wall polysaccharides not found in abundance in the cell walls of either species. The fate of these polysaccharides, if not exported and integrated into cell wall architectures, remains to be determined. The plant endoplasmic reticulum (ER)-Golgi apparatus is the site of synthesis, assembly, and trafficking of all non-cellulosic polysaccharides, proteoglycans, and proteins destined for the cell wall. As grass species make cell walls distinct from dicots and non-commelinid monocots, it has been assumed that the differences in cell wall composition stem from differences in biosynthetic capacities of their respective Golgi. However, immunosorbentbased screens and carbohydrate linkage analysis of polysaccharides in Golgi membranes, enriched by flotation centrifugation from etiolated coleoptiles of maize (Zea mays) and leaves of Arabidopsis (Arabidopsis thaliana), showed that arabinogalactan-proteins and arabinans represent substantial portions of the Golgi-resident polysaccharides not typically found in high abundance in cell walls of either species. Further, hemicelluloses accumulated in Golgi at levels that contrasted those found in their respective cell walls, with xyloglucans enriched in maize Golgi, and xylans enriched in Arabidopsis. Consistent with this finding, maize Golgi membranes isolated by flotation centrifugation and enriched further by free-flow electrophoresis (FFE), yielded over 200 proteins known to function in the biosynthesis and metabolism of cell wall polysaccharides common to all angiosperms, and not just those specific to wall type. We propose that the distinctive compositions of grass primary cell walls compared to other angiosperms result from differential gating or metabolism of secreted polysaccharides post-Golgi by an as yet unknown mechanism, and not necessarily by differential expression of specific synthase complexes. Keywords Plant Golgi, endoplasmic reticulum, cell wall polysaccharides, proteome, glycome, Zea mays (maize), Arabidopsis cell surface (Nebenführ and Staehelin, 2001). Numerous structural and enzymatic glycoproteins 133 that function at the plasma membrane and in the cell wall also transit through the Golgi. 134 Cellulose and callose synthases are trafficked through the Golgi membrane, as are receptor-like kinases, AGPs, other GPI-anchored proteins, and components of the cytoskeletal-plasma 136 membrane-cell wall signaling matrix (Dunkley et al. 2006; Heazlewood et al., 2007; Nikolovski 137 et al., 2012). Although we have a reasonably complete inventory of the polysaccharides and 138 Burget, E.G., Verma, R., Mølhøj, M., and Reiter, W-D. (2003) The biosynthesis of Larabinose in plants: Molecular cloning and characterization of a Golgi-localized UDP-Dxylose 4-epimerase encoded by the MUR4 gene of Arabidopsis. Plant Cell 15: 523-531. Caffall, K.H., and Mohnen, D. (2009) The structure, function, and biosynthesis of plant cell wall pectic polysaccharides. Carbohydr. Res. 344: 1879-1900. Carpita, N.C., and Shea, E.M. (1989) Linkage structure by gas chromatography-mass spectrometry of partially-methylated alditol acetates. In Analysis of Carbohydrates by GLC
Plant Cell Walls, 2001
Although the synthesis of cell wall polysaccharides is a critical process during plant cell growth and differentiation, many of the wall biosynthetic genes have not yet been identified. This review focuses on the synthesis of noncellulosic matrix polysaccharides formed in the Golgi apparatus. Our consideration is limited to two types of plant cell wall biosynthetic enzymes: glycan synthases and glycosyltransferases. Classical means of identifying these enzymes and the genes that encode them rely on biochemical purification of enzyme activity to obtain amino acid sequence data that is then used to identify the corresponding gene. This type of approach is difficult, especially when acceptor substrates for activity assays are unavailable, as is the case for many enzymes. However, bioinformatics and functional genomics provide powerful alternative means of identifying and evaluating candidate genes. Database searches using various strategies and expression profiling can identify candidate genes. The involvement of these genes in wall biosynthesis can be evaluated using genetic, reverse genetic, biochemical, and heterologous expression methods. Recent advances using these methods are considered in this review.
Molecular Plant, 2009
The CELLULOSE SYNTHASE-LIKE C (CSLC) family is an ancient lineage within the CELLULOSE SYNTHASE/CEL-LULOSE SYNTHASE-LIKE (CESA/CSL) polysaccharide synthase superfamily that is thought to have arisen before the divergence of mosses and vascular plants. As studies in the flowering plant Arabidopsis have suggested synthesis of the (1,4)b-glucan backbone of xyloglucan (XyG), a wall polysaccharide that tethers adjacent cellulose microfibrils to each other, as a probable function for the CSLCs, CSLC function was investigated in barley (Hordeum vulgare L.), a species with low amounts of XyG in its walls. Four barley CSLC genes were identified (designated HvCSLC1-4). Phylogenetic analysis reveals three well supported clades of CSLCs in flowering plants, with barley having representatives in two of these clades. The four barley CSLCs were expressed in various tissues, with in situ PCR detecting transcripts in all cell types of the coleoptile and root, including cells with primary and secondary cell walls. Co-expression analysis showed that HvCSLC3 was coordinately expressed with putative XyG xylosyltransferase genes. Both immuno-EM and membrane fractionation showed that HvCSLC2 was located in the plasma membrane of barley suspension-cultured cells and was not in internal membranes such as endoplasmic reticulum or Golgi apparatus. Based on our current knowledge of the sub-cellular locations of polysaccharide synthesis, we conclude that the CSLC family probably contains more than one type of polysaccharide synthase.
2020
Cellulose synthesis is essential for plant morphology, water transport and defense, and provides raw material for biomaterials and fuels. Cellulose is produced at the plasma membrane by Cellulose Synthase (CESA) protein complexes (CSCs). CSCs are assembled in the endomembrane system and then trafficked from the Golgi apparatus and trans-Golgi Network (TGN) to the plasma membrane. Since CESA enzymes are only active in the plasma membrane, control of CSC secretion is a critical step in the regulation of cellulose synthesis. However, the regulatory framework for CSC secretion is not clarified. In this study, we identify members of a family of seven transmembrane domain-containing proteins (7TMs) as important for cellulose production during cell wall integrity stress. 7TM proteins are often associated with guanine nucleotide-binding protein (G) protein signalling and mutants in several of the canonical G protein complex components phenocopied the 7tm mutant plants. Unexpectedly, the 7TM...
2015
Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Hebrew University, Rehovot 76100, Israel (D.B.-T., Y.A., R.E., S.H.-S.); Department of Bioinformatics and Genomics, University of North Carolina, Kannapolis, North Carolina 28081 (S.S., K.T., A.L.); Energy Biosciences Institute (A.d.S., M.P.) and Department of Plant and Microbial Biology (M.P.), University of California, Berkeley, California 94720; and Biology Department, University of North Carolina, Chapel Hill, North Carolina 27599 (J.J.K.)
S-Acylation of the cellulose synthase complex is essential for its plasma membrane localization
Science (New York, N.Y.), 2016
Plant cellulose microfibrils are synthesized by a process that propels the cellulose synthase complex (CSC) through the plane of the plasma membrane. How interactions between membranes and the CSC are regulated is currently unknown. Here, we demonstrate that all catalytic subunits of the CSC, known as cellulose synthase A (CESA) proteins, are S-acylated. Analysis of Arabidopsis CESA7 reveals four cysteines in variable region 2 (VR2) and two cysteines at the carboxy terminus (CT) as S-acylation sites. Mutating both the VR2 and CT cysteines permits CSC assembly and trafficking to the Golgi but prevents localization to the plasma membrane. Estimates suggest that a single CSC contains more than 100 S-acyl groups, which greatly increase the hydrophobic nature of the CSC and likely influence its immediate membrane environment.