Implication of a 5' coding sequence in targeting maternal mRNA to the Drosophila oocyte.

Early accumulation of maternal mRNA in one of the cells of the cluster of 16 cystocytes is a critical event in the determination of the Drosophila oocyte. A number of developmentally important mRNAs have been shown to accumulate in the early oocyte. We report here the early expression of the yemanuclein-alpha (yem-alpha) transcript, its accumulation in the germarial oocyte and its dynamic localization in the growing oocyte. We have investigated the mechanisms involved in these processes. Microtubules are likely to be involved in both transport and localization as was shown for other maternal transcripts which behave similarly. However, unlike all the cases reported so far, transport and localization are not dependent on 3'UTR sequences. We show that the 5' coding sequence is necessary for the early accumulation of yem-alpha RNA in the oocyte and for its localization pattern during oogenesis.