Biology Reference
In-Depth Information
the genome of nearly every arthropod of interest to both basic and applied sci-
entists. In 2011, a group proposed to sequence the genomes of 5000 species of
insects (and other arthropods) during the next 5 years (
Robinson et al. 2011
).
The initiative, called i5K, is meant to transform our understanding of insect biol-
ogy and improve our ability to manage pests.
7.13.1 Interesting Findings from Completed Genomes
Mining the genomes of the various arthropods sequenced to date will provide
new information for years to come, especially when functional analyses are con-
ducted in the laboratory to confirm proposed gene functions. Examples of key
discoveries as the result of whole-genome sequencing projects to date are pro-
vided below; these examples represent selected highlights and the full papers
should be read for additional insight and details. Much more will be learned as
additional studies are conducted using these genome sequences.
The genomes of three mosquitoes were sequenced:
Anopheles gambiae
,
Aedes aegypti
, and
Culex quinquefasciatus
(
Holt et al. 2002, Nene et al. 2007,
Arensburger et al. 2010
).
Severson and Behura (2012)
compared the results of
these efforts, in which
Cx. quinquefasciatus
seems to have the most genes
(18,883),
Ae. aegypti
has the next most (15,419), and
An. gambiae
has the fewest
(12,457). Genome sizes vary dramatically, with
An. gambiae
having a 289-Mbp
genome,
C. quinquefasciatus
having a 579-Mbp genome, and
Ae. aegypti
hav-
ing the largest genome with 1380 Mbp. The larger genome size of
Ae. aegypti
is
due to the fact that TEs comprise 50% of the genome. VectorBase (
http://www.
vectorbase.org/
)
contains the genomic data for these, and other insect or tick,
vectors of human pathogens.
Arensburger et al. (2010)
noted that
Cx. quinque-
fasciatus
has a significant expansion in olfactory and gustatory receptors, salivary
gland genes, and genes associated with detoxification.
Mita et al. (2004)
sequenced the genome of the long-domesticated
Bombyx mori
and compared the sex-determination system to that of
Drosophila
, finding that the
two systems differ greatly.
Xia et al. (2004)
provided a draft genome sequence, as
well, and found an estimated 18,510 genes, greater than the number found in
D.
melanogaster
. Approximately 1874 genes found are related to silk production.
The
Apis mellifera
genome was sequenced in 2006 (The
Honeybee Genome
Sequencing Consortium 2006
). It has few transposons compared with the other
genomes sequenced at the time, primarily consisting of
mariner
elements, and
evolved more slowly than
D. melanogaster
and the mosquito
An. gambiae
.
Apis
has fewer genes than
D. melanogaster
or
Anopheles
for innate immunity, as
well as fewer detoxification enzymes, cuticle-forming proteins, and gustatory
receptors, perhaps reflecting their social behavior within the protected hive.
