Parasitic genome sequenced in the battle to save honey bees

The genome of a parasitic mite that infects honey bee colonies and causes wide-spread destruction has been sequenced by scientists at the University of Liverpool and Xi’an Jiaotong-Liverpool University (University of Liverpool, 2017).

Although there are many potential causes for the decline in honey bee colonies, pathogens and parasites of the honey bee, particularly mites, are considered major threats to honey bee health and colonies.

The researchers sequenced the genome of the bee mite Tropilaelaps mercedesae to assess the interaction between the parasite and host as well as provide a resource for the ongoing battle to save honey bee populations. The results provide resources for developing gene-based control strategies, determining the weak points for conventional control methods, and identifying new targets for biological control.

T. mercedesae is a honey bee parasite prevalent in most Asian countries, and has a similar impact on bee colonies that the globally-present bee mite Varroa destructor has. More, T. mercedesae and V. destructor typically co-exist in Asian bee colonies and with the global trade of honey bees T. mercedesae is likely to become established worldwide.

The study, published in GigaScience, revealed that there were specific features in the T. mercedesae mite genome that had been shaped by their interaction with honey bees, and that current mechanisms to control mites are unlikely to be useful for T. mercedesae.

Dr Alistair Darby, from the University of Liverpool’s Centre for Genomic Research, where the sequencing was done, said “The genome sequence data and research findings provide useful resources for understanding mite biology and identifying potential gene-based mite control strategies.”

Of particular interest, the team found that the mite does not rely on sensing stimulatory chemicals to affect their behaviour, meaning that control methods targeted to gustatory, olfactory, and ionotropic receptors are not effective.

The researchers also found that T. mercedesae is enriched with detoxifying enzymes and pumps for the toxic xenobiotics, which means the mite can quickly acquire miticide resistance.

Relevant to this, the researchers investigated the bacteria that infect the bee mite, of which little is known. The scientists discovered that the symbiotic Rickettsiella grylli-like bacteria is commonly present in T. mercedesae, and suggest that manipulating this bacteria could help in the development of novel control strategies.

The extent of honey bee colony destruction remains a complex problem, but one that has an extensive impact on crop productivity since honey bees are needed for pollination of a variety of plants. The findings, genome, transcriptome, and proteome data from this T. mercedesae study add an important new resource in the battle to save bee colonies.

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