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.

 

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 5^th 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.