Biology Reference
In-Depth Information
6.6 Mapping the Ovary and Juvenile Hormone
Regulation by Vitellogenin
I argue in Chapter 7 that the traits involved in the pollen-hoarding syn-
drome are linked through a network of genes and hormones that regu-
late reproduction. h e next obvious question was whether the QTLs we
mapped for pollen hoarding and the suite of foraging traits associated
with pollen hoarding were also af ecting ovary size. We produced a
hybrid queen and backcrossed her to a high-strain male, generating a
distribution of genotypes and ovary phenotypes. We collected return-
ing foragers, weighed their nectar and pollen loads, dissected their
ovaries, and counted ovarioles. Bees that collected pollen had on aver-
age more ovarioles than those that collected only nectar or returned
empty.
We dissected newly emerged workers and counted their ovarioles.
h en we extracted their DNA to determine whether they inherited low-
or high-strain markers linked to each of the pollen-hoarding QTLs.
h is was a fast and ei cient way to look for candidate QTL ef ects on
ovarioles. We found direct ef ects of
pln2
and
pln3
and an interaction
ef ect of all four QTLs, thus demonstrating that the pollen-hoarding
QTLs were af ecting ovariole number and interacting in a complex way,
just as they do for the foraging traits.
It has been a mark of our research program to verify our i ndings
with bees other than the select strains. Allie Graham, a student of Olav
Rueppell's, mapped QTLs for ovariole numbers in a population of bees
derived from crosses of Africanized (AHB) and European honey bees
(EHB). We prescreened colonies of EHB and AHB that we had at the
bee lab in Mesa, Arizona, and identii ed AHB colonies that had high
ovariole counts and European colonies with low counts. We produced a
hybrid queen and backcrossed her to a drone from the high-ovariole
Africanized queen. h e resultant workers had the genes they inherited
from the hybrid queen mixed up in the egg gametes produced, but all
had a high-ovariole, AHB genome from the sperm of their father. h is
is the same as the breeding scheme used for mapping the high- and
low-strain behavioral traits. Workers were collected, ovaries were dis-
