Date of Award


Degree Type


Degree Name

Master of Science


Biochemistry and Cellular and Molecular Biology

Major Professor

Elena Shpak

Committee Members

Brad Binder, Albrecht Von Arnim


In plants stomata play a vital role for survival by allowing the gas exchange of CO2 [carbon dioxide] and water vapor to occur. A stoma is a central pore flanked by two kidney shaped guard cells and in wild type there is at least one pavement cell between each stoma. The ERECTA (ER) gene family consisting of ER, ERL1, ERL2 is involved in regulation of stomata development, where a triple mutant of er erl1 erl2 displays an increased stomata index and clusters of stomata that disobey the one cell spacing rule. To better understand the pathway of stomata development, we performed an ethyl methanesulfonate (EMS) screen in an enhancer erl1 erl2 background and looked for mutants with stomata clustering. A mutant with a strong stomata clustering phenotype was found and through map-based cloning the gene was identified as At1g08750 (renamed AtGPI8), a putative glycosylphosphatidylinositol-anchor (GPI) transamidase (GPI-T). In mammals and yeast the GPI-T is responsible for the cleaving of the C-terminal end of a protein and the attachment of the GPI anchor. Here we report the characterization of the partially functional atgpi8-1 and the lethal knockout atgpi8-2. We demonstrate how GPI anchored proteins (GPI-APs) play a role in fertility, growth, plasmodesmata permeability and stomata development. Furthermore, we investigate the involvement of a GPI-AP in the stomata development pathway. Genetic interactions have determined that the er family acts synergistically with atgpi8-1. A gain of function mutant of YDA has epistasis over atgpi8-1. Tmm and atgpi8-1 share similar phenotypes in leaves but tmm is epistatic over atgpi8-1 in stems. These results indicated that a GPI-AP protein functions upstream of YDA, and either downstream of or in concurrence with the ER family and TMM. Sequence analysis suggests that TMM could potentially be a GPI-AP in the stomata development pathway.

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