Analysis of oogenesis defects in Dyro mutant of Drosophila melanogaster.

Dyro mutant is female sterile, and oogenesis is aborted during stage8-9 of oogenesis. We investigated detail of the oogenesis defect of Dyro mutant. At first, we confirmed loss of Dyro caused female sterility by genetic rescue experiment. Then, we performed genetic mosaic analysis and found Dyro expression in germ cell is important for oogenesis. In Dyro mutant, inhibition of programmed cell death suppressed cell death of germ cells during oogenesis but failed to rescue fertility. It indicates that abortion of oogenesis is not because of mis-regulation of cell death signal but there is oogenesis defect which activates Caspase signaling pathway. Then, we observed Dyro mutant and looking for defects which may trigger cell death of germ cells in Dyro mutant. We found oogenesis abortion timing is similar to yolk protein mutant but different from amino acid starvation. It suggests that nutrient signal defect does not triggers cell death in Dyro mutant. We carefully observed the defect of Dyro mutant ovaries and found abnormal morphology of nucleolus and chromosome in nurse cells. It seems chromosome in Dyro mutant is thick and nucleolus is limited in small space between thick chromosomes in Dyro mutant nurse cells. Other defect we found is aggregated protein accumulation in germ cells. These data suggest that Dyro has important role in mid-oogenesis stage germ cell and loss of Dyro causes defect in nuclear of nurse cells which may leads to abortion of oogenesis.