Live imaging of endogenous RNA reveals a diffusion and entrapment mechanism for nanos mRNA localization in Drosophila.
BACKGROUND
Localization of nanos mRNA to the posterior pole of the Drosophila embryo directs local synthesis of Nanos protein that is essential for patterning of the anterior-posterior body axis and germ cell function. While nanos RNA is synthesized by the ovarian nurse cells and appears at the posterior pole of the ooctye late in oogenesis, the mechanism by which this RNA is translocated to and anchored at the oocyte posterior is unknown.


RESULTS
By labeling endogenous nanos RNA with GFP, we have been able to follow the dynamic pathway of nanos localization in living oocytes. We demonstrate that nanos localization initiates immediately upon nurse cell dumping, whereby diffusion, enhanced by microtubule-dependent cytoplasmic movements, translocates nanos RNA from the nurse cells to the ooctye posterior. At the posterior, nanos is trapped by association, in particles, with the posteriorly localized germ plasm. Actin-dependent anchoring of nanos RNA complexed to the germ plasm at the posterior maintains localization in the face of rapid cytoplasmic movements.


CONCLUSIONS
These results reveal a diffusion-based, late-acting posterior localization mechanism for long-range transport of nanos mRNA. This mechanism differs from directed transport-based localization mechanisms in its reliance on bulk movement of RNA.
Forrest
Kevin M
KM
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Gavis
Elizabeth R
ER
D000818:Animals; D019521:Body Patterning / Q000235:genetics; D003599:Cytoskeleton / Q000502:physiology; D004058:Diffusion; D004330:Drosophila / Q000196:embryology* / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics* / Q000502:physiology; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D018613:Microscopy, Confocal; D009865:Oocytes / Q000502:physiology; D009866:Oogenesis; D012333:RNA, Messenger / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D013194:Staining and Labeling; D019076:Transgenes / Q000235:genetics
D029721:Drosophila Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C070574:nos protein, Drosophila