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Title: Changes in Gene Expression Relating to Colony Collapse Disorder in honey bees, Apis mellifera

item JOHNSON, REED - University Of Illinois
item Evans, Jay
item ROBINSON, GENE - University Of Illinois
item BERENBAUM, MAY - University Of Illinois

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2009
Publication Date: 10/5/2009
Citation: Johnson, R., Evans, J.D., Robinson, G., Berenbaum, M. 2009. Changes in Gene Expression Relating to Colony Collapse Disorder in honey bees, Apis mellifera. Proceedings of the National Academy of Sciences. 106(35):14790-14795.

Interpretive Summary: Honey bees provide critical pollination services and a diverse set of products for human use. Sudden declines of honey bee colonies have been described during centuries of human beekeeping. Most recently, many honey bee populations in the United States suffered high losses, peaking in the winter of 2006-2007. Because of the suddenness and severity of these losses they were ascribed to ‘Colony Collapse Disorder (CCD). The causes of CCD are mysterious, and might involve chemical exposure, nutrition, or parasite pressures, or a combination of these. DNA microarrays provide an unbiased view of how honey bees in healthy and collapsing colonies differ with respect to key biological processes. We hope that these analyses can provide a ‘physical’ exam of bees and give insights into possible causes of CCD. We describe activity levels of genes involved with immunity and responses to chemicals, and show that the strongest correlates, as indicated by prior work, are with viral presence in bees and a change in the machinery used for protein production. CCD presents a huge threat to beekeepers and those needing pollination, and we anticipate these results and approaches can help researchers test scenarios for the root causes of this syndrome.

Technical Abstract: Colony collapse disorder (CCD) is a mysterious disappearance of honey bees that has beset beekeepers in the United States since late in 2006. Pathogens and other environmental stresses, including pesticides, have been linked to CCD, but a causal relationship has not yet been demonstrated. The gut, as a primary interface between the honey bee and its environment, is likely to be affected by CCD as it is a site of infection by pathogens as well as a site for detoxification of pesticides. We used whole-genome microrarrays to compare gene expression between guts of bees taken from CCD colonies originating on both the East and West Coasts of the U.S. and guts of bees from healthy historical samplings prior to the emergence of CCD. Considerable variation in gene expression was associated with the geographical origin of bees, but a consensus list of 65 transcripts was identified as potential genetic markers for CCD status. Reduced expression of two genes associated with detoxification and a mixed response from genes involved in immune function were observed. Of the probes for bee pathogens included on the array, the deformed wing virus (DWV), an Iflavirus, was more abundant in guts of CCD bees. Probes for the Israeli acute paralysis virus (IAPV), another picornavirus, were not included on the microarray, but this virus was detected only rarely using other methods. Unusual ribosomal RNA fragments were also conspicuously more abundant in CCD bee guts. The presence of these fragments may be a possible consequence of picornavirus infection. Ribosomal fragment abundance and viral presence may prove useful as diagnostic markers for colonies afflicted with CCD.