75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

143 The Ubiquitin-Specific Proteases of Arabidopsis thaliana
Jed Doelling 1 , Allison Phillips 2 , Gulsum Soyler-Ogretim 1 , Richard Vierstra 2
1
Division of Plant and Soil Sciences & The Genetics and Developmental Biology Program, West Virginia
University, Morgantown, WV 26506, 2 Department of Genetics, University of Wisconsin-Madison, Madison, WI
53706
The ubiquitin/26S proteasome pathway is a major pathway of selective protein degradation in eukaryotic organisms.
One class of enzymes essential to the function of this pathway is that composed of the ubiquitin-specific proteases
(UBPs). The UBPs serve to detach ubiquitin monomers 1) from the primary translation products of the polyubiquitin and
ubiquitin extension protein genes, 2) from multi-ubiquitin chains joined together via isopeptide linkages, and 3) from
ubiquitinated proteins. We are investigating the specific roles performed by particular UBPs in Arabidopsis thaliana
using a reverse genetic approach. We are currently analyzing a collection of T-DNA insertion lines that includes one
or more mutant lines for 26 of the 27 UBP genes found in Arabidopsis. In all of these lines, the insertion site is located
between the translational start and stop codons suggesting that homozygous individuals would be deficient in the function
of the corresponding protein. No aberrant phenotypes were observed for many of the single gene, homozygous mutant
individuals suggesting that the corresponding proteins are not essential or that other proteins may perform overlapping
functions. Double and triple mutant lines are being assembled via genetic crosses to investigate the functions of UBP
subfamilies. Particular UBP subfamilies appear to be essential for proper pollen development and function, for completion
of embryo development, and for proper development and/or function of the female gametophyte.
144 Characterization of Organ Patterning During Fruit Development in Arabidopsis thaliana
Amanda Durbak, Erica Hsiao, Frans Tax
University of Arizona, Tucson, AZ, USA
While the fruit of a flowering plant plays an essential role in species propagation by housing developing seeds and
aiding in their dispersal, the mechanisms that underlie intercellular signaling in patterning of fruit organ number remain
unknown. Work in tomato has shown that increase in both organ number and cell division are responsible for larger fruit,
but the molecular mechanism through which these two components are integrated and contribute to overall patterning and
size is still not clear. While some mutants with organ number defects such as the clavata mutants have been identified in
Arabidopsis, a mechanism of generation of extra organs has not yet been elucidated. In order to identify new mutants that
have fruit patterning defects, we have implemented an EMS mutagenesis screen to look for plants that produce siliques
with extra valves and margins. From this screen we have identified two new clv1 or clv2 alleles and two mutants that
map to regions in the genome that are not known to contain genes involved in fruit patterning. Further characterization
of the newly identified mutants along with previously identified mutants utilizing cell-type specific markers is being
used to analyze changes in morphology, specification, and cell proliferation in mutant fruit. These studies will help to
determine the key differentiation events responsible for fruit patterning.