Body of Abstract: Arabinogalactan-proteins (AGPs) are implicated in various plant growth and development processes. In recent years, my lab has studied the genes/enzymes which glycosylate AGPs. We have focused on eight Hyp-O-galactosyltransferases (GALT2–6, HPGT1–3), which are responsible for adding the first sugar, galactose, onto AGPs and three β-glucuronosyltransferases (GLCAT14A, 14B and 14C), which add glucuronic acid to AG chains. Due to gene redundancy among the GALT and GLCAT genes, single or double galt or glcat genetic knockout mutants are not sufficient to fully reveal the biological functions of these genes/enzymes. Consequently, we have used CRISPR-Cas9 gene editing/multiplexing technology to generate higher-order knockout mutants for members of the GALT and GLCAT gene families. Such mutants demonstrate the functional importance of the carbohydrate moiety of AGPs in above ground growth and development, root growth, root hair growth, trichome branching, pollen development, silique development, seed set, seed coat mucilage accumulation, seed germination, sexual reproduction, and embryo development. Higher-order galt and glcat mutants produced and characterized in my lab provide insight into the relationship between AGP sugar decorations and various biological functions attributed to AGPs. These mutants are now being used to examine the mechanism(s) of action by which AGPs execute their functions.