Ferns are ideal for evolutionary and developmental studies. Molecular studies tracing fern evolution are especially important because there is a paucity of morphological characters for use in systematic studies and taxonomists disagree about the unity of some traits. In this research, the investigator will study the organization of the genomes in several fern families. Genome rearrangements are valuable for determining linkage at higher orders of taxonomic classification where comparisons of restriction site mutations are precluded because the genetic distance is too great. It is likely that one could trace the evolution of the rearrangements by finding representatives that are immediate between the primitive fern Osmunda and the higher ferns. The investigator will collect and analyze the old world tree ferns for chloroplast DNA mutations and compare these results to data on new world tree ferns. One current hypothesis, which has some support from angiosperm studies, is that species from the old and new worlds that look alike differ more than different species which are in close proximity to each other. The study described would address this issue. Ferns also offer several potentially valuable features for studying gene regulation. The haploid generation is a small, fully independent plant that grows from a single cell (the spore) and can be bisexual. Unlike flowering plants, self fertilization produces a diploid plant that is 100% homozygous in one generation. Transformation of the spore will allow the investigator to generate plants homozygous for the introduced trait. The particular genes that will be examined are male determining genes. Spores of certain species that are sown in the presence of the hormone antheridiogen germinate to produce a male haploid plant. This suggests that a different gene(s) is activated in response to this hormone than when the spore is sown without the hormone and in isolation from other gametophytes. Subtraction hybridization will be used to enrich for specific messages related to these two different developmental pathways.
