Abstract
The incorporation of 3H-uridine into ovarian RNA of Bombyx mori has been studied by means of electrophoresis and autoradiography. In normal ovaries, synthetic activity of RNA, including ribosomal, transfer and other kinds of RNAs, was shown to be most active during later half stages of pupal life and concurrent increase of RNA contents was observed. In ovaries of mutant smn, RNA synthesis remained at low level throughout pupal development, though electrophoretic analysis of the RNA demonstrated the presence of various species of RNAs similar to those of normal genotype. That the ovarian RNA synthesis took place in nurse cells and follicle cells but not in oocytes was shown through short term labeling (3hr) experiment. Synthesized RNAs were transported from nurse cells to egg-chamber via intercellular bridge, RNA grains flowed first into central part of the oocyte, then migrated towards periphery regions. No sign of RNA transfer from follicle cells to oocytes could be observed. Labelings could not be found in oocyte of smn ovary, though distributed in both nurse cells and follicle cells in rather low densities, the tendency was more pronounced in the latter that corresponded to the inherent absence of choriogenesis in this mutant. Present results suggest that RNAs in the egg cell depend entirely upon the nurse cell synthesis followed by transfer through intercellular bridge. Nurse cell RNAs if not transfered to the oocyte, as in the case of smn, seem to be degenerated soon or later.
