Abstract
Organellar DNA degradation in plants is sensitive to the physiological state such as developmental stage and senescence. However, the underlying mechanism is unknown so far. Angiosperm pollen is a good experimental system because organellar DNA is degraded dramatically during pollen development. We performed screening to isolate mutants defective in organellar DNA degradation. Pollens from a mutagenized population were stained with DNA-specific fluorescent dye, DAPI, and observed using a fluorescent microscope. Wild-type pollen showed DAPI signals from the nuclei of vegetative and sperm cells, while mutant candidates exhibited additional signals in the cytoplasm. Among the mutant candidates was the 1411 mutant that also showed additional variegation phenotype. The responsible gene of the 1411 mutant encoded the large subunit of the ribonucleotide reductase (RNR) enzyme. The enzyme ensures adequate and balanced deoxyribonucleotide pool. Characterization of pollens and variegation phenotypes in several RNR mutants including 1411 will be presented.
