While the genetic technologies available for using in Anopheles mosquitoes and Anopheles gambiae in particular continue to expand, most rely on integrating transgenes into germ-lines to create genetically modified lines of mosquitoes.
Of course, there is direct injection of dsRNA into various life stages, which is a means of transiently silencing some genes.
There is no equivalent method to transiently overexpress genes in Anopheles mosquitoes.
In Aedes mosquitoes, Sindbis virus has been modified to be an expression vector but these are not useful in Anopheles mosquitoes.
Suzuki, et al (2014) have reported on an improved version of a densovirus-based expression system developed earlier using Anopheles gambiae densovirus (AgDNV). AgDNV was modified so it can accommodate approximately 800bp of exogenous DNA. Modified densovirus are injected into the thorax of adults and in approximately 3 days the authors could see evidence of transgene expression (EGFP). Expression was prolonged and could be seen more than two weeks after injection. AgDNV showed distinct tropisms with fat body and ovaries most readily infected.
So this system will have some utility for those working with Anopheles gambiae. It is a great example of how viruses have the potential to serve as delivery systems for genes and transgenes in insects.
Suzuki et al (2014) also demonstrated how multiple proteins can be expressed in the limited confines of the AgDNV genome. Of course, viruses have evolved numerous ways to deal with this problem of packing lots of information into their usually small genomes. They used 2A-like sequences to link three different coding regions. 2A is a self-cleaving peptide sequence of viral origin. So from one promoter it is possible to express multiple proteins by linking their coding regions with 2A sequences. This is a good ‘trick’ that could be applied more widely in insect transgenics-based studies.
A viral over-expression system for the major malaria mosquito Anopheles gambiae
Yasutsugu Suzuki, Guodong Niu, Grant L. Hughes, & Jason L. Rasgon
Scientific Reports 4, Article number: 5127 doi:10.1038/srep05127