Recent Topics Posters
Di Stilio, Veronica , Chen, Xuening .
The genus Thalictrum in the study of the genetics of sex determination.
Previous work has shown that dioecious species of the genus Thalictrum, in particular T. dioicum, provide a suitable system for the study of the developmental and genetic aspects of dioecy and sex determination. The main interesting developmental feature of T. dioicum is the unisexual nature of flowers from the earliest observable stages of development. Other desirable features for a good model system would include evidence for genetic rather than environmental sex determination, and a workable genome size. In dioecious T. dioicum, we have found 1:1 sex ratios of carpellate to staminate plants in five different controlled crosses. Adult plants collected from the field had a constant sex expression throughout 4 years (n=16), suggesting the absence of sex lability. These two results point to a stable genetic sex determination system in this species. No heteromorphic sex chromosomes were observed so far, and no consistent differences in genome size between carpellate and staminate plants were detected by flow cytometry. We are currently investigating meiosis in pollen mother cells, searching for early segregating pairs of homologs, which would point to incipient sex chromosomes. Chromosome observations on mitotic root tips showed that T. dioicum has a complement of 2n=28, indicating that it is a tetraploid if we consider x=7 to be the basic number for the genus. In spite of being polyploid, the very small chromosome size typical of this genus results in a C-value of aproximately 900 Mbp, a workable genome size for molecular biology endeavors. C-value estimates were extended to 23 additional species in an attempt to understand polyploidy and its possible relation to breeding system evolution in the genus. Preliminary data shows an overall trend of smaller genome sizes in hermaphroditic species (with one exception) and bigger genomes in andromonoecious and dioecious taxa.
1 - University of Washington, Department of Biology, Box 351800, Seattle, WA, 98195
Presentation Type: Poster
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM