Nuclear and cytoplasmic chloroplast mutants induced by chemical mutagens in Mimulus cardinalis: Genetics and ultrastructure.

The modes of inheritance of chemically induced chlorophyll-deficient phenotypes in Mimulus cardinalis reveal that the chloroplast is controlled by the genome and the plastome. Three of the chlorophyll-deficient mutants in M. cardinalis are inherited through nuclear recessive genes and two are inherited through plastome genes. One chlorophyll-deficient mutant was sterile and could not be analyzed genetically. Ultrastructural analysis of the six mutant types reveals that each possesses a unique defective chloroplast type(s) in comparison to the genotypically and phenotypically normal chloroplasts. Based on plastid ultrastructure it seems reasonable to assume that the mutations, genome and plastome, are non-allelic or at least significantly different forms of the same allele. The isolation of these types of mutants provide suitable material needed to study the effects of specific biochemical blocks and the elucidation of developmental pathways leading to chloroplast biogenesis. The mutants also provide valuable information concerning the interrelationship between the nucleic acid of the genome and the plastome.