A Cytoplasmic Regulatory Mutant of Euglena: Constitutivity for the Light-Inducible Chloroplast Transfer RNAs

An ultraviolet-induced cytoplasmic mutant (G(1)BU) of Euglena gracilis Klebs var. bacillaris Pringsheim is described. G(1)BU, in addition to being golden in color and containing smaller amounts of chlorophyll than wild type when grown in the light, is a regulatory constitutive mutant for the light-inducible chloroplast isoleucine and methionine tRNAs; i.e., these two tRNAs are present in dark-grown G(1)BU cells at approximately the levels present in light-grown wild-type cells. Six other mutants were also examined for normal control of plastid tRNA biosynthesis; all four of the aplastidic mutants (lacking appreciable plastid structures and detectable plastid DNA) are incapable of chloroplast tRNA biosynthesis, whereas two other color mutants that do contain plastids and chloroplast DNA have normal plastid tRNA regulation.