MATERNAL EFFECT FOR GENES ENCODING 6-PHOSPHOGLUCONATE DEHYDROGENASE AND GLUCOSE-6-PHOSPHATE-DEHYDROGENASE IN DROSOPHILA-MELANOGASTER

The maternal effect for 2 enzymes of the pentose cycle, 6-phosphogluconate dehydrogenase (6PGD) and glucose-6-phosphate dehydrogenase (G6PD) were studied in D. melanogaster using a genetic system based on the interaction of Pgd- and Zw- alleles, which inactivate 6PGD and G6PD, respectively. The presence and formation of the enzymes were investigated in those individuals that had not received the corresponding genes from the mother. Maternal forms of the enzymes were detectable up to the pupal stage. The activities of maternal 6PGD and G6PD per individual increased 20- to 30-fold from the egg stage to the 3rd larval instar even in the absence of normal Pgd and Zw genes. Immunologic studies showed that the increase in 6PGD activity is due to an accumulation of the maternal form of the enzyme molecules. A hybrid isozyme resulting from an aggregation of the subunits of isozymes controlled by the genes of the mother and embryo itself was seen. The maternal effect in the case of 6PGD is due to a long-lived stable mRNA transmitted with the egg cytoplasm and translated during the development of D. melanogaster.