Honeybees with Colony Collapse Disorder Show Their Genes

A new study, from the Agricultural Research Service, takes a closer look at the genes of honeybees decimated by colony collapse disorder.

| August 28, 2009

The first hard evidence of what is happening physiologically inside bees during Colony Collapse Disorder (CCD) has been published in a new study by Agricultural Research Service (ARS) and University of Illinois scientists in the Proceedings of the National Academy of Sciences. The study also looked at differences in activity levels of critical genes in CCD and healthy bee colonies.

Using a tool called a genome-wide microarray, the scientists found a large amount of abnormal ribosomal RNA (rRNA) fragments in the guts of honeybees in CCD colonies. Ribosomes are the cellular factories in which proteins are made, guided by rRNA, and a large amount of abnormal rRNA fragments means the protein construction system is compromised. This indicates that honeybees in colonies diagnosed with CCD had reduced ability to synthesize new proteins.

The gut is the primary entry point for pathogens and pesticides in honeybees. Honeybees' stress response systems also can be measured in the bee's gut. The honeybee has two separate response systems: one to environmental stresses such as pesticides, and a different one reacting to pathogens such as viruses. 

This was the first time RNA levels have been measured in honeybees as a way of tracking whether it is honeybees' pesticide response system or their pathogen immune response system that is reacting in CCD, according to ARS geneticist Jay Evans, who works in the Bee Research Laboratory at the ARS Henry A. Wallace Beltsville (Maryland) Agricultural Research Center. Evans was part of a team that included entomologists May R. Berenbaum, Reed M. Johnson and Gene E. Robinson from the University of Illinois.

In CCD colonies, the genes involved in the pathogen/immune response systems showed no single clear pattern of activity, although there was commonly more activation of these genes and the bees had a higher overall level of viruses and other pathogens than non-CCD colonies.

Almost all CCD colonies had a higher level of picorna-like viruses, which attack the ribosome. Picorna-like viruses that attack honeybees include deformed wing virus and Israeli acute paralysis virus. The varroa mite, a major honeybee parasite, is known to transmit picorna-like viruses.

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