The plant cell wall is composed of complex polysaccharides and a small amount of structural proteins and cell wall enzymes. Arabinogalactan-proteins (AGPs) are highly glycosylated, hydroxyproline-rich structural proteins that play important roles in plant growth and development. AtAGP17, 18 and 19 comprise the lysine-rich classical AGP family in Arabidopsis. They consist of an N-terminal signal peptide, a classical AGP domain disrupted by a short basic lysine-rich subdomain and a C-terminal glycosylphosphatidylinositol (GPI) anchor addition sequence. A previous study showed a null T-DNA insertion mutant of AtAGP19 displayed pleiotropic phenotypes. Here, a microarray approach was employed to elucidate changes in gene expression associated with the atagp19 mutant. The expression of several genes related to cell expansion were found to change significantly. Interestingly, one gene (At1g68720 , cytidine/deoxycytidylate deaminase family protein) adjacent to AtAGP19 was found to be down-regulated about 50 fold and RT-PCR showed the absence of mRNA for this gene in the atagp19 mutant. Furthermore, complementation with the 3’ portion of the At1g68720 gene can fully restore all the wild type phenotypes, indicating this region is critical for the functions revealed by the agp19 mutant. To examine cellular localization of the lysine-rich AGPs, GFP-AtAGP17/18/19 fusion proteins as well as a GFP control were overexpressed in Arabidopsis plants and the fusion proteins were present on the plant cell surface. Plasmolysis of leaf trichome cells further determined the localization of the fusion proteins at the plasma membrane. Moreover, in vitro pollen germination showed that AtAGP17, unlike LeAGP-1 (the lysine-rich AGP in tomato), was not associated with pollen tube elongation. To further elucidate AtAGP17/18/19 function(s), transgenic Arabidopsis overexpressing AtAGP17/18/19 without the GFP tag were produced. AtAGP18 overexpressors displayed several phenotypes distinct from the wild type plants: they were short and bushy, had short roots and produced less viable seeds. In contrast, the vector control transformants as well as the AtAGP17/19 overexpressors had the same phenotypes as the wild type plants. Furthermore, AtAGP18 was down-regulated by the plant hormone ABA, indicating ABA may be involved in AtAGP18 function(s). Finally, the expression pattern of AtAGP14 (At5g56540), an AG peptide in Arabidopsis was examined. AtAGP14 was highly expressed in flowers and young roots and moderately expressed in seedlings, stems and rosette leaves. A plate-based phenotypic analysis was also carried out for the T-DNA insertional mutant of AtAGP14 and wild type Arabidopsis but no significant differences were observed with respect to germination rate, true leaf numbers, primary root length and lateral root numbers.