The genomes of 16 species of mosquito have been read in a new study to shed light on why only some species of the insect can transmit malaria to humans.
Malaria is one of the world's most common infectious diseases, leading to hundreds of millions of cases and up to a million deaths every year. The plasmodium parasite that causes the disease is spread by anopheles mosquitoes. There are more than 500 species members in this family, so it's surprising that only about 40 of them are actually major players in the spread of malaria.
To find out why, Wellcome Sanger Institute scientist Mara Lawniczak, together with a large consortium of collaborators internationally, set about read the DNA sequences of 16 representative anopheles species.
"People sent us squashed mosquitoes in tubes from different parts of the world, we got the DNA out, read and then assembled it," says Lawniczak.
The results, published in the journal Science, provide an important starting point for studying how mosquitoes interact with humans and the malaria parasite and can also highlight regions of the genome that might be responsible.
"We've got regions of the genome that are consistently similar in malaria-spreading mosquitoes, so those will be areas to focus on."
The team also looked at how the levels of relatedness between the different species and also how much DNA they were capable of swapping amongst themselves.
"Despite being different species," explains Lawniczak, "some of these family members can nonetheless still interbreed under certain conditions."
This can spell trouble because it means that disease-linked traits can swap between the mosquitoes, potentially turning non-malaria-spreading species into vectors for the disease. It can also mean that the insects become harder to control.
"We found that the two most distantly related species in our study had - despite the long evolutionary gap separating them - clearly swapped some big portions of DNA in recent times. And this is important because exchanges like this could traffic - for instance - genes for resistance to insecticides, which would make malaria much harder to control."