Biology Reference
In-Depth Information
many functions and are used in many ways. I think of them as door-
bells. Many houses and buildings have them. When you ring the door-
bell, the door opens, but you i nd very dif erent things inside. Because
of the broad ef ects of IIS pathways and their known ef ects on develop-
ment, hormonal networks, reproduction, and metabolism, we decided
to look at them more carefully.
h e i rst step was to look at the expression of the dif erent IIS genes
in high- and low-strain bees. Genes are expressed when copies of them
are being made in cells. However, the genes are made of deoxyribonu-
cleic acid (DNA), but the expressed copies are made of ribonucleic acid
(RNA). h ere are only subtle dif erences, but the dif erences make the
RNA suitable as templates (messengers) for cells to make proteins (lon-
ger sequences of amino acids) and peptides (shorter sequences of amino
acids). If we found signii cantly dif erent amounts of messenger RNA
(mRNA) in high- and low-strain bees for specii c genes, it could be an
indication that those genes were af ecting our phenotypes. If we didn't
i nd dif erences, it would not mean that those genes are not the QTLs
we mapped, just that the dif erences are not based on the current
amounts of circulating mRNA. h e genes themselves could be dif erent
with respect to structure and function of the proteins and peptides they
encode. We looked at worker larvae, newly emerged adults, and forag-
ers and found expression dif erences in two of six IIS genes.
PDK1
(pln3)
was expressed at a higher level in the fat body of foragers from
the high strain.
HR46 (pln2)
was expressed at a higher level in low-
strain bees of all life stages.
PDK1
and
HR46
were now candidate genes
of special interest.
h e next step was to see whether expression of
PDK1
and
HR46
var-
ied with ovary size. We studied workers derived from a high backcross
and looked for the association of gene expression and ovariole number
that was presumably inherited from the hybrid queen, as we did in
Section 6.3. We i rst looked at the association of ovariole number and
foraging behavior. We found the normal associations, consistent with
dif erences between high- and low-strain foragers: bees with more
ovarioles were more likely to collect pollen, pollen foragers foraged ear-
lier in life, and bees that foraged earlier in life for nectar collected nec-
