Biology Reference
In-Depth Information
Many aspects of the complex eusocial life style of the honey bee are being
deciphered with ongoing functional analyses (
Adams et al. 2008, Chan et al.
2008
).
The beetle
Tribolium castaneum
had its 160-Mbp genome completed in
2008 (
Tribolium
Genome Sequencing Consortium 2008
). The beetle is a pest of
stored products and has a large expansion in odorant and gustatory receptors.
Its expansion of P450 and other detoxification enzymes may make it prone to
developing resistance to pesticides used for its control. Its development is “more
representative of other insects than is
Drosophila
” in both gene content and
function. It exhibits short-germ band development and also has a systemic RNA
interference (RNAi) capacity (which
D. melanogaster
lacks), although its system
is different from that in
C. elegans
. One third of the genome consists of repeti-
tive DNA.
The first parasitoid genome sequenced was that of
Nasonia vitripennis
(
Nasonia
Genome Working Group 2010
). This tiny wasp is a gregarious endopar-
asitoid of dipteran pupae. The larvae feed gregariously within fly pupae, emerg-
ing as adults from the puparium. Genome sequences confirm that substantial
amounts of
Wolbachia
DNA were transferred into its genome. The
Nasonia
genome also includes a strong presence of odorant-binding, gustatory-receptor,
odorant-receptor, and venom-protein gene families, which is to be expected in
a species that uses chemical cues to locate and inject venoms into hosts during
oviposition. Interestingly, 60% of the
Nasonia
genes have a human ortholog,
18% are arthropod-specific, and 2.4% seem to be specific to the Hymenoptera.
Approximately 12% seem to be specific to
Nasonia
. Because
Nasonia
feeds on
an amino-acid-rich diet as larvae and adults, it seems to have lost some amino-
acid metabolic pathways, reflecting its parasitic biology. The analysis of venom
genes was of particular interest, and 79 candidate venom proteins were identi-
fied, some of which were unrelated to any known insect venoms.
The human body louse,
Pediculus humanus humanus
, genome was com-
pleted in 2010 (
Kirkness et al. 2010
).
Pediculus
is an obligatory parasite of
humans and a vector of human pathogens. The louse has a primary endosym-
biont
Candidatus
Riesia pediculicola, and its genome also was sequenced. The
body louse has a small genome (108Mbp), with 10,773 protein-coding genes.
The genome contains relatively fewer genes associated with environmental
sensing and response, including odorant and gustatory receptors and detoxify-
ing enzymes, perhaps relevant to its relatively protected parasitic life style. One
unusual finding was that the louse has 18 minicircular chromosomes in the mito-
chondrion (compared with one chromosome in most arthropods). The symbiont
