The distinctive roles of five different ARC genes in the chloroplast division process in Arabidopsis

ARC (accumulation and replication of chloroplasts) genes central different aspects of the chloroplast division process in higher plants. In order to e stablish the hierarchy of the ARC genes in the chloroplast division process and to provide evidence for their roles, double mutants were constructed b etween arc11, arc6, arc5, arc3 and arc1 in all combinations and phenotypica lly analysed, arc11 is a new nuclear recessive mutant with 29 chloroplasts compared with 120 in wild type. All the phenotypes of the double mutants ar e unambiguous. ARC1 downregulates proplastid division but is on a separate pathway from ARC3, ARC5, ARC6 and ARC11. ARC6 initiates both proplastid and chloroplast division. ARC3 controls the rate of chloroplast expansion and ARC11 the central positioning of the final division plane in chloroplast di vision. ARC5 facilitates separation of the two daughter chloroplasts. ARC5 maps to chromosome 3 and ARC11 and ARC6 map approximately 60 CM apart on ch romosome 5.