Pattern formation in plants depends upon the precise spatial and temporal control of cell growth. To dissect the molecular mechanisms controlling pattern formation, these investigators have isolated Arabidopsis mutants with altered body organizations. One of these mutants, emb30, is unable to form a true root, a true hypocotyl, stems, or flowers. Instead, most emb30 seedlings contain only abnormal cotyledon tissue and sometimes an abnormal shoot apical meristem. As a result, emb30 mutants are seedling lethals. Microscopy analysis has shown that EMB30 is essential for normal cell division, cell expansion, and cell adhesion in plants and molecular studies have revealed that a region in the predicted EMB30 protein is similar to a region in the yeast Sec7 protein, which is involved in the secretory pathway. The PIs have termed this region the Sec7 domain. Two other open reading frames, one from humans and one from C. elegans, also contain Sec7 domains. The goal of this proposal is to define the specific role of EMB30 in cell growth and organ development. Cell biology and molecular techniques will be employed to examine the effect emb30 mutations have on undifferentiated tissue and adult organ development. Experiments in which the EMB30 gene is placed under the control of an inducible promoter will also allow the examination of the role of EMB30 in the initiation and maintenance of organs, such as the root. To elucidate the specific function of EMB30 in plant cell growth, the components of processes that have been shown or suggested to be affected in emb30 mutants, such as glycoproteins and the cell wall, will be analyzed. The subcellular localization of the EMB30 protein will also be determined. Experiments to determine if EMB30 can complement a yeast sec7 mutant will also be performed. In addition, an Arabidopsis EMB30 homolog will be cloned and characterized. These experiments should elucidate the specific function of EMB30 in particular, and provide i nsight into the processes regulating cell growth and pattern formation, in general.
