Biology Reference
In-Depth Information
Reduction of Vg increases JH and thus response to sugar. We were
probably looking at an ef ect of Vg knockdown on the physiological ag-
ing of bees, one of the components of the pollen-hoarding syndrome.
7.5.4 Vg Knockdown in High- and Low-Strain Bees
High-strain bees forage earlier in life than do low-strain bees. In fact,
Jennifer Fewell and I noticed very early in the selection program that
many low-strain bees failed to forage at all. h ey would die at er 40 to
50 days without initiating foraging. Gro Amdam knocked down Vg in
newly emerged high- and low-strain workers and assayed their JH ti-
ters when they were 7 days old. High-strain bees, like wild types of
other studies, had elevated JH, but the low-strain bees showed no re-
sponse. Selection for low pollen hoarding apparently “uncoupled” the
double-repressor regulatory system in low-strain bees but let it intact
in highs.
Because the low-strain bees show no JH response to Vg, we had a tool
to look at ef ects of the reproductive regulatory network by knocking
down vitellogenin expression. If the reproductive regulatory network
involving JH and Vg are regulating foraging behavior, then we should
see a response to Vg knockdown in the high strain but not in the low.
Kate Ihle used dsRNA to knock down Vg in newly emerged workers of
the high- and low-pollen-hoarding strains. Knockdown high-strain
bees foraged earlier in life and demonstrated a bias for nectar relative to
the high-strain controls. h is result was the same as that observed by
Mindy Nelson and Kate Ihle discussed in Section 7.5.2. As predicted,
there was no response to knockdown in the low-strain bees.
h ere is one necessary caveat to the story of the double-repressor re-
lationship of Vg and JH. David Antonio and colleagues knocked down
Vg in bees from a single colony of Africanized honey bees. h e Vg-
knockdown bees initiated long-term l ights, assumed to be foraging
l ights, 3 to 4 days earlier in life than the controls. h is was as we
found. However, they found low levels of JH in 7-day-old knockdown
bees. In this case, low Vg stimulated onset of early foraging even
though JH stayed low. JH apparently played no role, as in the case of the
