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General Comment |
Huynh J, et al reported that Bazooka and PAR-6 are required with PAR-1 for the
maintenance of oocyte fate in Drosophila.
The anterior-posterior axis of C. elegans is defined by the asymmetric division of the
one-cell zygote, and this is controlled by the PAR proteins, including PAR-3 and
PAR-6, which form a complex at the anterior of the cell, and PAR-1, which localizes at
the posterior. PAR-1 plays a similar role in axis formation in Drosophila: the
protein localizes to the posterior of the oocyte and is necessary for the localization of
the posterior and germline determinants. PAR-1 has recently been shown to have
an earlier function in oogenesis, where it is required for the maintenance of oocyte fate
and the posterior localization of oocyte-specific markers. Here, the authors show that the
homologs of PAR-3 (Bazooka) and PAR-6 are also required to maintain oocyte fate.
Germline clones of mutants in either gene give rise to egg chambers that develop 16
nurse cells and no oocyte. Furthermore, oocyte-specific factors, such as Orb protein
and the centrosomes, still localize to one cell but fail to move from the anterior to the
posterior cortex. Thus, PAR-1, Bazooka, and PAR-6 are required for the earliest
polarity in the oocyte, providing the first example in Drosophila where the three
homologs function in the same process. Although these PAR proteins therefore seem
to play a conserved role in early anterior-posterior polarity in C. elegans and
Drosophila, the relationships between them are different, as the localization of PAR-1
does not require Bazooka or PAR-6 in Drosophila, as it does in the worm.
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