Glycome and proteome components of Golgi membranes are common between two angiosperms with distinct cell wall structures

Authors: OKEKEOGBU, IKENNA - Purdue University; PATTATHIL, SIVAKUMAR - University Of Georgia; GONZALEZFERNANDEZ-NI, SUSANA - Lawrence Berkeley National Laboratory; ARYAL, UMA - Purdue University; Penning, Bryan; LAO, JEEMENG - Lawrence Berkeley National Laboratory; HEAZLEWOOD, JOSHUA - Lawrence Berkeley National Laboratory; HAHN, MICHAEL - University Of Georgia; MCCANN, MAUREEN - Purdue University; CARPITA, NICHOLAS - Purdue University

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2019
Publication Date: 3/26/2019
Citation: Okekeogbu, I.O., Pattathil, S., Gonzalez Fernandez-Nino, S.M., Aryal, U.K., Penning, B., Lao, J., Heazlewood, J.L., Hahn, M.G., McCann, M.C., Carpita, N.C. 2019. Glycome and proteome components of Golgi membranes are common between two angiosperms with distinct cell wall structures. The Plant Cell. https://doi.org/10.1105/tpc.18.00755.
DOI: https://doi.org/10.1105/tpc.18.00755

Interpretive Summary: The plant ER-Golgi apparatus is the site of synthesis, packaging and export of all non-cellulosic polysaccharides and proteins of the cell wall. Here, we establish that a carbohydrate matrix of mostly arabinogalactan proteins is common to angiosperm species that possess the two distinct types of 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. The full complement of cell-wall polysaccharides, and the synthases and glycosyl transferases that make them, are independent of the polymers that are exported and integrated into the cell wall. The findings are helpful to understand that knowledge of the composition of the cell walls rather than gene expression alone is important for scientists or those in industry to more easily convert plant material into useful, sustainable bio-based products or energy.

Technical Abstract: The endoplasmic reticulum (ER)-Golgi apparatus is the site of synthesis, assembly, and trafficking of all non-cellulosic polysaccharides and peptidoglycans destined for post-Golgi compartments and the cell wall. Immunosorbent-based 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 a majority of the resident polysaccharides were in an AGP/RG-I class not typically found in high abundance in cell walls of grasses. Despite the large differences in the polysaccharide constituents of the cell walls of eudicots and grasses, the carbohydrate profiles were common to Golgi membranes from both Arabidopsis and maize. Maize Golgi membranes isolated by flotation centrifugation were enriched further by free-flow electrophoresis (FFE), yielding 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 the grass cell wall. We propose that the distinctive compositions of grass cell walls result from differential gating or metabolism of secreted polysaccharides post-Golgi and not necessarily by differential expression of specific synthase complexes in these species compared to those of other angiosperms.