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Blowfly Genome Provides Clues for Curbing Flystrike Infections

Australian sheep blowfly

NEW YORK (GenomeWeb) – By sequencing the genome of the blowfly, a team reporting in Nature Communications hopes to provide resources to thwart the agricultural pest, which causes a disfiguring and sometimes deadly condition called flystrike.

Researchers from the University of Melbourne and elsewhere sequenced the genome of the blowfly Lucilia cuprina, assembling together a 458 million base draft genome for the parasite. Together with a newly generated transcriptome sequence for the L. cuprina, the genome sequence provided clues to the fly's protein-coding repertoire, including genes involved in host interactions and resistance to insecticide.

"[W]e are now at a point of being able to use the present L. cuprina genome and transcriptome resources to address key biological questions, and to facilitate the development of improved tools for blowfly prevention and control in the future," University of Melbourne veterinary and agricultural sciences researcher Robin Gasser, the study's corresponding author, and colleagues wrote.

"These resources will also support comparative investigations of a range of parasitic dipterans," the study's authors added.

Blowflies can create both serious financial burdens and animal welfare issues, causing a disease called myiasis, or flystrike, in which blowfly larvae feed on skin and secretions of host animals such as sheep.

To prevent these infections, the researchers noted, it's sometimes necessary to surgically remove wool-bearing skin from susceptible parts of the sheep's body — particularly in odor-rich regions around the tail. Insecticides aimed at diminishing flystrike are available as well, though resistance is rising and there are concerns over unwanted chemical residue in the resulting animal products.

As part of the 5000 Insect Genome Project (i5k), authors of the blowfly genome analysis used a combination of Illumina sequencing and ALLPATHS-LG assembly to put together a draft genome assembly spanning more than 458 million bases at a depth of 100-fold, on average.

Nearly 58 percent of the genome was made up of repeat sequences, the researchers reported, though it also contained an estimated 14,544 protein-coding genes. Of those, at least 10,121 gene predictions were supported by the team's RNA sequence data.

That collection contained just over 4,100 single copy genes orthologous to those in the genomes of the fruit fly, Drosophila melanogaster; the house fly Musca domestica; and the tsetse fly Glossina morsitans. Another 12,160 blowfly genes resembled those in at least one of the other flies, while more than 2,000 genes appeared to be unique to L. cuprina.

When the researchers looked at the predicted functions of the blowfly genes, they found an abundance of sequences coding for transcription factors, transport and pore proteins, and enzymes.

In addition to putting the blowfly head-to-head with sequences from other flies, the team compared transcriptome sequences in male and female blowflies from different life cycle stages — analyses that offered insights into everything from blowfly reproduction and development to their ability to parasitize host animals and subsist on various food sources.

Using both the newly available blowfly sequences and the related Drosophila model organism, the researchers began ferreting out the roots of insecticide resistance in the blowfly, focusing on five genes previously implicated in resistance.

Conversely, the team also scoured the genome for drug and vaccine targets that may be exploited to combat blowfly parasitism, using homology with Drosophila to help narrow in on dozens of candidate genes and proteins.

For instance, the researchers found that the blowfly carries a gene resembling a Drosophila transcription factor that regulates female accessory glands and is thought to be essential for reproduction.