9632675 Wolfe A detailed and strongly supported phylogeny of a group of organisms provides a framework or road map for critical studies of growth, development, and life history. Dr. Andrea Wolfe at Ohio State University is taking advantage of just such phylogenetic knowledge to explore molecular evolutionary changes in photosynthesis in plants that have become parasitic. The Scrophulariaceae/Orobanchaceae group of plants includes autotrophic, fully photosynthetic species (the snapdragons for example), so-called hemiparasites that form root attachments to other plants, and heterotrophic, non-photosynthetic parasites like beechdrops (genus Epifagus) and others. The parasites must attach themselves to host plants to absorb carbon nutrients for survival; the phylogenetic tree for this group demonstrates that parasites have evolved from photosynthetic forms in several lineages. Dr. Wolfe is analyzing genes for the light-harvesting thylakoid apparatus of the chloroplast, to determine changes in nuclear and plastid genes involved in photosynthetic energy transfer. Questions she is addressing include: are there "key innovations" at the molecular level that channel a plant toward parasitism; what are the patterns and sequence of mutations in nuclear and plastid genes as photosynthetic function is lost; are there backup or complementary gene systems to chloroplast activities, as mutations damage or destroy critical enzymes of photosynthesis? Modern tools of molecular biology make possible the fine-scale genetic dissection of enzymatic processes of light-harvesting and energy-capture during photosynthesis in plants. Taking advantage of phylogenetic knowledge of plant groups that include parasitic species, Dr. Wolfe has designed an imaginative program of study that looks closely at the decay of photosynthetic function in a series of plant species that have evolved an increasingly parasitic mode of life. In so doing, she is analyzing critical stages in the evolution of biochemical pathways and also help ing to understand shifts in life history in plant evolution.
