9631048 Hays An understanding of mutagenic and antimutagenic processes in plants will be enhanced by knowing the baseline rates of somatic mutation, before modulation by any internal selection process and by understanding more about how plant genome-fidelity activities reduce mutational loads. Those insights will be gained by developing in Arabidopsis thaliana a versatile somatic-mutation assay system, based on reversion of reporter-gene alleles, by initiating searches for Arabidopsis "mutator" mutants, by isolating and analyzing plant mismatch-repair genes, and by beginning to study the effects of UV mutation and mismatch-repair on recombination in Arabidopsis. %%% The fixed locations, obligatory exposure to sunlight and oxygen-producing metabolism subject plants to a variety of environmental mutagens. Nevertheless, estimated somatic mutation frequencies in trees and annuals do not suggest ongoing error catastrophes. Thus, plants may employ unusually powerful genome-fidelity functions. This study will begin to investigate those mechanisms. ***
