Poster: Late and Moved Abstracts

Abs # 1032: Mutations in the SUPERMAN gene affect both gametophytic and sporophytic development of Arabidopsis ovules

Presenter:	Gaiser, J. Christopher , cgaiser@linfield.edu
Authors	Gaiser, J. Christopher  (A)   Brown, Melanie L. (A)
Affiliations:	(A): Biology Department, Linfield College

Our laboratory studies genes that govern ovule development in Arabidopsis thaliana. The SUPERMAN (SUP) gene plays two distinct roles in flower development: it ensures that stamens are established in the correct number and position, and it is responsible for the asymmetric growth of the ovule's outer integument. Arabidopsis plants carrying mutations in the sup gene exhibit aberrant carpel morphology and uniform growth of the outer integument (rather than the asymmetric growth characteristic of wild type ovules). Thus, sup plants are almost completely sterile. Previous work showed that some of this infertility was due to the altered carpel morphology of sup plants, and that the remainder was due to the ovules themselves. That is, both the carpel phenotype and the ovule phenotype contribute to the infertility exhibited by superman mutants. The goal of this study was to determine the cause of the reduced fertility of superman ovules. The sporophytic abnormality of sup ovules does not seem to effect initial gametophytic development. Formation of a megaspore mother cell and subsequent mitoses occur normally. However, later gametophyte development is adversely affected in approximately 25% of sup ovules. Beginning at the 4-nucleate stage, nuclear migration in these sup ovules occurs in a manner that precludes nuclear fusion and formation of a diploid central cell, leading to sterile ovules. At maturity, these ovules have eight haploid nuclei, rather than six haploid nuclei and one diploid nucleus as in wild type ovules.