INFECTION OF THE GERM-LINE BY RETROVIRAL PARTICLES PRODUCED IN THE FOLLICLE CELLS - A POSSIBLE MECHANISM FOR THE MOBILIZATION OF THE GYPSY RETROELEMENT OF DROSOPHILA
Su. Song et al., INFECTION OF THE GERM-LINE BY RETROVIRAL PARTICLES PRODUCED IN THE FOLLICLE CELLS - A POSSIBLE MECHANISM FOR THE MOBILIZATION OF THE GYPSY RETROELEMENT OF DROSOPHILA, Development, 124(14), 1997, pp. 2789-2798
The gypsy retroelement of Drosophila moves at high frequency in the ge
rm line of the progeny of females carrying a mutation in the flamenco
(flam) gene. This high rate of de novo insertion correlates with eleva
ted accumulation of full-length gypsy RNA in the ovaries of these fema
les, as well as the presence of an env-specific RNA, We have prepared
monoclonal antibodies against the gypsy pol and Env products and found
that these proteins are expressed in the ovaries of flam females and
processed in the manner characteristic of vertebrate retroviruses, The
Pol proteins are expressed in both follicle and nurse cells, but they
do not accumulate at detectable levels in the oocyte, The Env protein
s are expressed exclusively in the follicle cells starting at stage 9
of oogenesis, where they accumulate in the secretory apparatus of the
endoplasmic reticulum, They then migrate to the inner side of the cyto
plasmic membrane where they assemble into viral particles, These parti
cles can be observed in the perivitelline space starting at stage 10 b
y immunoelectron microscopy using anti-Env antibodies, We propose a mo
del to explain flamenco-mediated induction of gypsy mobilization that
involves the synthesis of gypsy viral particles in the follicle cells,
from where they leave and infect the oocyte, thus explaining gypsy in
sertion into the germ line of the subsequent generation.