Identification and characterization of seven ROP GTPases in Zea mays

Graduation date: 2004Regulation of cell division and expansion are critical for plant development. The mechanisms that control these processes are not clearly understood in higher plants. In other eukaryotic models it has been shown that the highly conserved Rho family GTPases play a crucial role in these mechanisms. One distinct subset of the Rho GTPases, designated Rop, is present in higher plants and may play a role in cellular morphogenesis. I have conducted an initial molecular characterization of genes encoding ROPs in the monocot in Zea mays (maize), and also isolated mutant alleles in two of these genes using TUSC methodology (in collaboration with Pioneer Hi- Bred International, Inc.). The molecular analysis revealed phylogenetically-related subsets within the rop gene family, and multiplex RT-PCR assays indicated differing relative expression levels for the different genes in different plant tissues. These data thus indicated the potential for unique functions for each maize ROP, and provided clues to assist in phenotypic characterization of mutations in each gene. My initial characterization of heritable Mu insertion alleles in the rop6 and rop7 genes was assisted by the development of a rapid PCR-genotyping assay to identify single and double mutant homozygotes. Likely null alleles for both rop6 and rop7, based on RT-PCR analysis, were identified; however, no mutant phenotype could be identified in either single or double mutant homozygotes. These results suggest that although these genes may serve specialized roles in plant signaling, there is also some degree of redundancy providing functional overlap for these monomeric signaling proteins