The embryo of the common fruit fly (Drosophilia) develops based on a body plan that is set by maternal-effect genes, which are expressed in the mother. In this paper, the nos protein produced by the maternal-effect gene nanos is found to be necessary for the abdomen to form. In addition, if nos is not produced, blocking the maternal-effect gene hunchback can restore the abdomen. These results suggest that the nos gene product blocks the activity of the gene product hb of maternal hunchback.
Maternal-effect genes produce mRNA transcripts that are then deposited in the egg cells in a concentration gradient along the front and back of the egg. The transcripts are then translated into proteins, and the amounts of these proteins in different locations of the cell determine the body structure that part of the cell will eventually become. While the concentration gradient of nos in the embryo is required for the abdomen to form, a concentration gradient of hb is required for parts of the head and thorax to form.
The purpose of the research was to determine whether the hb maternal gene product is a primary factor in determining the development of the lower body in Drosophilia embryos.
The scientists examined the physical characteristics, or phenotypes, of embryos that lacked maternal nos and both maternal hb and nos to test the effects of the maternal hb gene product. Pole cell transplantation was used to create the maternal donor for embryos without maternal hb because embryos lacking hb do not survive to reproduce. When there was no maternal nos gene product but both maternal and zygotic hb were intact, the embryo was missing an abdomen (Figure 2a). However, embryos missing both maternal nos and hb developed normally (Figure 2d). Removing maternal hb along with maternal nos restored the normal phenotype. This suggests that the nos gene product suppresses the function of the maternal hb gene product.
This relationship between nos and hb highlights how maternal-effect genes can drastically influence development. From this study, we learned that the maternal nos gene product acts to suppress the function of the maternal hb gene product in the development of a Drosophilia embryo. Without nos, a removal of hb can rescue the normal lower body development. In addition, this paper highlights the pole cell transplantation method in creating fertile embryos that can’t be produced by crossbreeding.