I have a master
degree in molecular biology from Lund University, and I’ve always had an
interest in all things touching upon evolution (i.e. life!), and how molecular events correlate with phenotypic
changes as well as how ecological changes can affect the genotypic level. In
September 2008 I started my PhD studies here in the Pheromone group, working
under the title “Evolution of novel
pheromone systems in moths”. My current subproject involves the sister
group of Lepidoptera, which is Trichoptera (the caddisflies), that we believe
could give us some information about how certain genes, that our group are
interested in, might have evolved. A description about this project can be
found further down this page. Feel free to contact me with questions about my
projects, suggestions etc.
Project I: Desaturase evolution
Insects make up
75% of all described species in the world, and affect us humans as being pollinators
of our crops as well as being pests, vectors of diseases, and as providing
biovariance in the world, which we tend to take for granted. Many moths are
pests on crops and in warehouses, so in order to control their abundance
without exterminating them, it is necessary to know as much as possible about
their behaviour and molecular biology.
When searching
for a mate, moths rely on pheromones, which are specific mixes and ratios of
chemical compounds that elicit a behavioural response when a con-species
perceives it. Generally, moths use long chain fatty acid derivatives (from
either palmitic or oleic acid). In this respect they differ them from the primitive
moths and the sister group of the Lepidoptera, the caddisflies (Trichoptera). Everything
points to that this type of pheromone evolved in the early evolution of
Lepidoptera, before the divergence into the heteroneuran lineages (Löfstedt et al. 2004).
There are specific
genes involved in biosynthesis of pheromones, and changes in their expression
and functionality could affect the production of the pheromone signal severely.
For example, a change in the pheromone composition could lead to reproductive
isolation, or to a scenario where only a small amount of males would respond
(so called "rare males") (Linn et
al. 2003). Such genes are potential speciation-genes.
One type of
genes that are strongly associated to the pheromone biosynthesis are the
multigene family of desaturases, which encodes enzymes that introduce double
bonds in the carbons chain, resulting in a unique signature of the chemical
structure. The desaturase genes are believed to have been subject to one or
many gene duplications in the genome(s) of the ancestor(s) of moths today,
giving rise to the many variants we can find among all the Lepidopterans, such
as the Δ9 and the Δ11 desaturases (Knipple et
al. 1998). The Δ11 desaturase is so far specific for moths. The most recent
information on its evolution is the presence of a copy in Lampronia capitella, stating that the duplication occurred in the
early evolution of the Lepidoptera (Lienárd et
al. 2008).
Rhyacophila nubila is a caddisfly native to the Swedish fauna.
It produces heptan-2-one, heptan-2-ol, nonan-2-one, and nonan-2-ol as its
putative pheromone compounds (Löfstedt et
al. 1994), which does not indicate a desaturase activity due to the lack of
double bonds. But the possibility remains that there could be untranscribed or
untranslated copies in the genome, such as psuedogenes or partial relics of the
initial duplication.
|
|
|
|
|
Heptan-2-ol
|
Heptan-2-one |
Nonan-2-ol
|
Nonan-2-one
|
Project
II: Reductase evolution
In addition
to the desaturases, there is another multigene family involved in pheromone
biosynthesis. These are the reductases, enzymes capable of reducing the
carbonyl carbon and thus converting the fatty-acyl precursors to their
corresponding alcohols (Moto et al.
2003). To be able to gain as good
insight as possible to the evolution of pheromone systems, the variance,
functions, and specificities of the reductases must also be elucidated.
The small
ermine moths, Yponomeuta, are a Lepidopteran
group consisting of several species, where some are of industrial interest due
to being pests on crops and landscapes. Since these species are closely
related, yet produce different pheromone compounds, they are a suitable group
for studies on reductase evolution.
References:
Knipple, D.
C., Rosenfield, C. L., Miller, S. J., Liu, W., Tang, J., Ma, P., W. K., and
Roelofs, W. L. (1998). Cloning and
functional expression of a cDNA encoding a pheromone gland-specific acyl-CoA D11-desaturase of the
cabbage looper moth, Trichoplusia
ni. Proceedings of the National Academy of Sciences 95: 15287-15292.
Liénard, M.
A., Strandh, M., Hedenström, E., Johansson, T., and Löfstedt, C. (2008). Key biosynthetic gene subfamily recruited
for pheromone production prior to the extensive radiation of Lepidoptera.
BMC Evolutionary Biology 8: 270.
Linn, C.,
O’Connor, M. Jr., and Roelofs, W. (2003). Silent
genes and rare males: A fresh look at pheromone blend response specificity in
the European corn borer moth, Ostrinia nubilalis. The Journal of Insect Science 3: 1-6.
Löfstedt,
C., Hansson, B. S., Petersson, E., Valeur, P., and Richards, A. (1994). Pheromonal secretions from glands on the 5th
abdominal sterine of hydropsychid and ryacophilid caddisflies (Trichoptera).
Journal of Chemical Ecology 20:
153-169.
Löfstedt,
C., Zhu, J., Kozlow, M. V., Buda, V., Jirle, E., Hellqvist, S., Löfqvist, J.,
Plass, E., Franke, S., and Francke, W. (2004). Identification of the sex pheromone of the currant shoot borer Lampronia
capitella. Journal of Chemical Ecology 30:
643-658.
Moto, K.,
Yoshiga, T., Yamamoto, M., Takahashi, S., Okano, K., Ando, T., Nakata, T., and
Matsumoto, S. (2003) Pheromone
gland-specific fatty-acyl reductase of the silkmoth, Bombyx mori. Proceedings of the National Academy of
Sciences 100: 9156-9161.