The Drosophila plutonium and pan gu genes regulate entry into S phase at fertilization

Abstract

Mutations in the Drosophila maternal genes plutonium ( plu) and pan gu ( png) have the striking phenotype that DNA replication initiates in unfertilized eggs. Fertilized eggs from plu or png mutant mothers also have a mutant phenotype; DNA replication is uncoupled from nuclear division, resulting in giant, polyploid nuclei. Analysis of multiple alleles of these genes indicates that their wild-type function is required to maintain repression of DNA replication until fertilization. The phenotype of two png alleles suggests that this gene also may play a direct role in coupling S phase and mitosis during the early cleavage divisions. We describe genetic interactions among png, plu, and the previously identified gene gnu that demonstrate these three genes regulate the same process.