Eukaryotic cells rely on the interactions of the nuclear and organeller genomes for normal growth and development. Coordinate expression of these independent genomes during the formation of the energy transducing complexes of the mitochondria and chloroplast is essential. We are studying the interactions of nuclear and chloroplast genomes in the coordinate expression of the photosynthetic apparatus by genetic and molecular means. Expression of a number of photosynthetic proteins, both chloroplast and nuclear encoded, is translationally regulated during the biogenesis of the chloroplast in Chlamydomonas reinhardtii. We have characterized a group of nuclear mutants which are deficient in translation of specific chloroplast encoded mRNAs. We will clone the nuclear genes encoding these chloroplast transnational activators by complementation of the photosynthetic mutants via DNA dependent transformation, a process recently developed in may lab. Studying the expression of these transnational activators during chloroplast biogenesis should provide a basis for understanding the role of nuclear genes in regulating organeller gene expression.
