Abstract
bicoid mRNA localises to the Drosophila oocyte anterior from stage 9 of oogenesis onwards to provide a local source for Bicoid protein for embryonic patterning. Live imaging at stage 9 reveals that bicoid mRNA particles undergo rapid Dynein-dependent movements near the oocyte anterior, but with no directional bias. Furthermore, bicoid mRNA localises normally in shot2A2, which abolishes the polarised microtubule organisation. FRAP and photo-conversion experiments demonstrate that the RNA is stably anchored at the anterior, independently of microtubules. Thus, bicoid mRNA is localised by random active transport and anterior anchoring. Super-resolution imaging reveals that bicoid mRNA forms 110-120 nm particles with variable RNA content, but constant size. These particles appear to be well-defined structures that package the RNA for transport and anchoring.
Highlights
MRNA localisation is a widely-used mechanism for targeting proteins to the regions of the cell where they are required and is often coupled to translational repression to prevent expression of the encoded protein until after its transcript is localised (Lecuyer et al, 2007; Jambor et al, 2015)
In Drosophila, the anterior-posterior axis is determined by the microtubule-dependent localisation of bicoid and oskar mRNAs to the anterior and posterior poles of the oocyte, respectively (Pokrywka and Stephenson, 1991; Clark et al, 1994; Roth et al, 1995). bcd mRNA is translationally repressed during oogenesis and is only translated when the egg is laid, providing a local source of Bcd protein, which diffuses to form a morphogen gradient that patterns the anterior half of the embryo (Ephrussi and St Johnston, 2004)
The original genomic bicoid-MS2 transgenes expressed full-length bcd mRNA from its endogenous promoter fused to 6 copies of the MS2 stem loop (Weil et al, 2006), but the relatively low numbers of MS2 coat protein (MCP)-GFP bound per RNA and the low expression levels made the RNA hard to image, in fast moving particles
Summary
MRNA localisation is a widely-used mechanism for targeting proteins to the regions of the cell where they are required and is often coupled to translational repression to prevent expression of the encoded protein until after its transcript is localised (Lecuyer et al, 2007; Jambor et al, 2015). Long Oskar anchors its own RNA, whereas short Oskar nucleates the polar granules, leading to the posterior recruitment of the germ line determinants and the abdominal determinant, nanos mRNA (Wang and Lehmann, 1991; Ephrussi and Lehmann, 1992; Vanzo and Ephrussi, 2002) Both bcd and osk mRNAs are transcribed in the nurse cells within the germline cyst and are transported along microtubules through the ring canals into the oocyte by Dynein (Clark et al, 2007; Mische et al, 2007).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
