An international research team has successfully mapped the genome of the bed bug (Cimex lectularius) to get a better understanding of its genetic makeup. The findings — by researchers from 36 institutions — have been published in the journal Nature Communications.
The genome is sort of like the bed bug’s blueprint. Now that the scientists have identified all of the genes that are in a bed bug, they can then figure out which ones are critical for its survival.
“This paper provides a publicly accessible resource that scientists can use to develop new and specific targets for bedbug control,” said Dr. Ed Vargo, one of the co-authors.
Notably, they discovered 805 possible instances of genes being transferred from bacteria within the bed bug to the insect’s chromosomes — a process called lateral gene transfer (LGT). Of those 805 instances, 459 have been attributed to the Arsenophonus bacteria, and 87 from Wolbachia, both of which are common bacterial associates of insects.
The researchers extracted DNA and RNA from preserved and living collections, including samples from a population that was first collected in 1973 and has been maintained since then. RNA was sampled from males and females representing each of the bug’s six life stages, before and after blood meals, in order to paint a full picture of the bedbug genome.
“It’s not enough to just sequence a genome, because by itself it does not tell the full story,” said Mark Siddall, another one of the co-authors. “In addition to the DNA, you want to get the RNA, or the expressed genes, and you want that not just from a single bed bug, but from both males and females at each part of the life cycle. Then you can really start asking questions about how certain genes relate to blood-feeding, insecticide resistance, and other vital functions.”
The researchers found that the number of genes was fairly consistent throughout the bed bug life cycle, but they observed notable changes in gene expression, especially after the first blood meal. Some genes, expressed only after the bed bug first drinks blood, are linked to insecticide resistance, including mechanisms that result in better detoxification. This suggests that bed bugs are likely most vulnerable during the first nymph stage, potentially making it a good target for future insecticides.
The genome also shows that bed bugs have developed multiple ways of resisting insecticides. Their armor-like outer cuticle sports barriers and detoxification genes that help prevent insecticides from penetrating. Many bed bugs have also evolved new forms of sodium channels, gates in the nerve cells that insecticides such as pyrethroids are designed to target and disrupt. The bugs might also detoxify ingested pesticides using the same robust antioxidant enzyme system they use to detoxify blood.
The researchers said that pesticide companies could leverage these genomic resources to screen the effectiveness of available chemicals, lowering the cost of getting new insecticides to market.
“The sequencing, assembly, annotation and manual analyses of the C. lectularius genome provide an important and timely resource for understanding the biology of this human ectoparasite,” the authors wrote. “It will also serve as a gateway for the discovery of new targets for control of bed bug populations.”
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