BRC Science Highlight Understanding the mechanism of mixed-linkage glucan synthesis and accumulation in the cell wall of grasses Objective Determine the subcellular localization of mixed-linkage glucan (MLG) and evaluate the effects of MLG synthase overexpression on plant growth and MLG accumulation. Approach Conduct imaging analyses using immunogold labeling and transmission electron microscopy to detect MLG and xylan in wild-type plant sections, immunofluorescence to detect MLG in sections of stems from MLG synthase over-expressing lines, and confocal laser scanning microscopy of live cells of MLG synthase overexpressing lines. Analyze the effects of MLG over-accumulation in MLG synthase overexpressing plants. Fluorescently tagged CSLF6, the major MLG synthase, is localized at the Golgi apparatus in epidermal cells of new emerging leaves of 5-week old Brachypodium plants. Results/Impacts MLG was found to be present in the Golgi apparatus, in post-Golgi structures, and in the cell wall. CSLF6, the major MLG synthase, was found to be localized to the Golgi. Overproduction of MLG causes developmental and growth defects in growing plants (Brachypodium and barley). Together, these results indicate that MLG production occurs in the Golgi similarly to other cell wall matrix polysaccharides, and supports the broadly applicable model in grasses that tight mechanisms control optimal MLG accumulation in the cell wall during development and growth. Future studies that build upon this work will enable the development of efficient strategies to overcome limitations in increasing MLG levels in plants, a promising strategy to increase yields of bioenergy crops. Notes: text Title again: Text 1-2 sentence summary? Kim, S.-J. et al. “In the grass species Brachypodium distachyon, the production of mixed-linkage (1,3;1,4)-β-glucan (MLG) occurs in the Golgi apparatus.” The Plant Journal (2018) [DOI: 10.1111/tpj.13830]. GLBRC March 2018