The work proposed here will study the effects of somatic variation on the population biology and evolution of plants by examining somatic changes of nuclear DNA. Two aspects of genomic change will be studied: 1) the occurrence of rapid genomic changes in response to environmental variation, and 2) the accumulation of somatic mutation. Plants have been chosen as model systems because they are particularly amenable to the study of somatic change. Plants can attain great ages, thus mutations accumulate over time. In addition, plants appear to have flexible genomes which respond to environmental pressures. The proposed studies will measure the accumulation of somatic mutations in long-lived individuals of Pinus longaeva, the Bristlecone Pine, and in ancient clones of Solidago altissima, a species of undisturbed prairies. Somatic changes in ribosomal DNA and in the alcohol dehydrogenase gene will be determined using standard DNA technologies. These studies will determine the rate of somatic change over time and the influence of somatic mutation on genetic variation within populations. The experimental induction of rapid genomic change in response to variable environments will be studied in both Solidago and Taraxacum, an asexually reproducing species. The work proposed here examines fundamental genetic processes which have potential importance for the genetics and evolution of plant species. Moreover, somatic variation occurs in all organisms and has been implicated in the process of ageing and in the generation of tumoricity. The work proposed here will provide detailed knowledge of the rate and accumulation of somatic variation and thus will provide information which is of potential use in the study of age dependent genetic changes in humans.
