| Abstract Detail
Protein Modification and Turnover Soyler-Ogretim, Gulsum [1], Doelling, Jed [2]. Pag1, the alpha7 subunit of 20S proteasome, is essential for pollen function. The Ubiquitin/26S proteasome pathway of selective protein degradation is important in many developmental pathways including embryo and pollen development, response to hormones and environmental stress, and cell division. The proteins to be degraded by this pathway are tagged by the covalent attachment of a ubiquitin chain as regulated by a specific three-step enzymatic cascade. The major fate of ubiquitin-tagged proteins is degradation by the 26S proteasome. The 26S proteasome is composed of one or two 19S regulatory particles and a 20S core particle. Whereas the 19S regulatory particle is involved in the recognition of ubiquitin-tagged proteins, degradation of the target protein occurs within the inner chamber of the cylindrical 20S core particle. The 20S core particle consists of 4 stacked rings each containing 7 different proteins: the two inner rings are composed of beta subunits and two outer rings are composed of alpha subunits. Whereas two genes of highly-similar sequence encode many of the alpha and beta subunits in Arabidopsis, only one gene is known to encode the alpha subunit PAG1. Mutant plants, carrying a T-DNA insertion within PAG1, were analyzed to determine the contribution of PAG1 to growth and development. Here we show that a functional copy of PAG1 is essential for pollen function in Arabidopsis thaliana. Pollen from heterozygous PAG1/pag1 plants was analyzed by DAPI, fluorescein diacetate, and Alexander staining, pollen germination assays, and limited crosses. Our results show that PAG1 does contribute somewhat to pollen viability but the development of most pollen grains appears to proceed normally. Genotypic analysis of the progeny of reciprocal crosses between wild-type and heterozygous PAG1/pag1 plants indicated that transmission of the mutant pag1 allele through the pollen is impaired. The same result was obtained even if only a limited number of pollen grains were used in the crosses. This suggests that mutant pollen will not be successful in pollination even in the absence of competing wild-type pollen.
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1 - West Virginia University, Plant and Soil Sciences, 478 Harding Ave #5, Morgantown, WV, 26505, USA
2 - West Virginia University, Plant and Soil Sciences
Keywords:
20S proteasome
Pag1
ubiquitination
pollen
protein degradation.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P37010
Abstract ID:874 |
