STABLE ALBINISM INDUCED WITHOUT MUTAGENESIS - A MODEL FOR RIBOSOME-FREE PLASTID INHERITANCE

Maternally inherited chlorophyll deficiency, or albinism, is a standar d marker in plant cytoplasmic genetics. Its stability is consistent wi th mutations in the plastid genome. Nuclear mutations inducing plastid ribosome deficiency (PRD) also lead to maternally inherited chlorophy ll deficiency. Here we report that stable chlorophyll deficiency can b e efficiently generated in cruciferous plants without mutagenesis by a short exposure to spectinomycin, an inhibitor of plastid protein synt hesis. We show that the chlorophyll-deficient phenotype results from a deficiency in plastid ribosomes and plastid translation products. Los s of plastid ribosomes is irreversible. The data suggest that mutation s are not essential for generating inheritable PRD. It allows the form ulation of a more general model in which stable PRD can be induced by a variety of factors that prevent the formation of functional plastid ribosomes. A non-mutational mechanism for generating inheritable chlor ophyll deficiency has implications for the origin and inheritance of g reen-white variegation in nature.