Christina Grozinger, Ph.D.

Current Graduate Students:

Holly Holt
Elina Lastro Niño
Daliris Ramírez

Postdoctoral Scholars:

Sarah Kocher
Amy Toth

Department Focus Area:

Genomics, Chemical Ecology

Research Interests :

Social insects, behavioral genomics, neuroethology, chemical ecology

Teaching:

• Genes and Behavior Seminar (Spring 2009)
• Ecological Genomics (TBA)
• Insect Neurogenomics (TBA)

Research Activities & Interests:

The effect of reproduction on honey bee queen physiology, behavior and pheromone production.

Honey bees have a number of reproductive states, including virgin queens, laying virgin queens, instrumentally inseminated queens, and naturally mated queens (Winston 1987) . For these different reproductive states, we can monitor behavior (ie, egg-laying behavior or taking mating flights) pheromone production, ovary activation, and gene expression in both the brain and ovaries using microarray analysis. Queen pheromone production, in particular, is critical to colony organization and health, since it regulates many aspects of worker behavior (including worker reproduction and foraging) and inhibits rearing of new queens and swarming, which can reduce colony strength (Slessor et al. 2005) . Ultimately, our goal is to understand the physiological processes that cause post-mating changes in queens. At the molecular level, we hope to match gene expression patterns with specific physiological or behavioral changes. These studies will identify candidate genes and pathways that can serve as the basis for further functional analyses or as markers for breeding programs. This research has been conducted by two graduate students (Sarah Kocher and Elina Lastro Nino) and a post-doctoral associate (Freddie-Jeanne Richard, now an assistant professor at University of Poitiers, France), in collaboration with Professor David Tarpy (NCSU). It is supported by funding from USDA-NRI, the Eastern Apiculture Society, and the Florida Department of Agriculture and Consumer Services.

We have found that brain gene expression and queen pheromone profiles are significantly modified by insemination quantity, in studies using instrumentally inseminated and natural mated queens (Kocher et al. 2008; Richard et al. 2007) . Furthermore, workers are attuned to these differences and are preferentially attracted to the pheromone produced by multiply mated queens. Our studies have demonstrated that both stretch receptors in the oviducts and seminal proteins appear to trigger post-mating changes (Richard et al. in prep, Kocher et al submitted) . Given that instrumental insemination is critical for honey bee breeding and selection (particularly to prevent accidental mating with Africanized bees), these results will allow us to develop modifications to the instrumental insemination process to further improve queen quality and colony health. These studies suggest that the production of queen pheromone is exquisitely sensitive to factors associated with reproduction and mating. Future studies in collaboration with Abraham Hefetz (Tel Aviv University, supported by a US-Israel Binational Science Foundation grant) will focus on the biosynthetic processes that regulate pheromone production.

Modulation of pheromone responsiveness in worker bees.

While responses to pheromones are typically considered to be instinctive and hard-wired, it is clear that responses can be modulated by environmental context, or the physiology and genotype of the receiving individual. We are studying the molecular mechanisms underlying modulation of response to queen mandibular pheromone (QMP). QMP is rather unusual pheromone, in that it can cause both short-term changes in behavior (attraction the pheromone source) and long-term changes in behavior and physiology, including inhibiting rearing of new queens and worker reproduction, and slowing the transition from nursing to foraging (Slessor et al. 2005) . QMP causes profound changes in brain gene expression, significantly altering expression of hundreds of genes (Grozinger et al. 2003) . Furthermore, these brain expression profiles correlate with the behavioral effects of QMP.

We have demonstrated that the short- and long-term responses QMP can be uncoupled; thus, they appear to operate by different mechanisms (Grozinger et al. 2007) . Furthermore, modulation of physiological state (ie, nurses vs foragers, or treatment with a juvenile hormone analog) can affect responses to pheromone (Grozinger and Robinson 2007) . We are now expanding our studies to consider genotypic modulation of responses to QMP (Kocher and Grozinger, submitted). These studies are supported by a 2008 NSF CAREER grant.

We have initiated a series of studies using a pheromone-responsive gene, Kr-h1, identified in our microarray analysis (Grozinger et al. 2003) . We have studied physiological factors that modulate its expression, and have found that it is regulated by juvenile hormone (Grozinger and Robinson 2007) and cGMP (Fussnecker and Grozinger 2008) . In collaboration with Tzumin Lee (University of Massachusetts, Worcester), we have found that it plays an important role in regulating neuronal properties and structure in Drosophila (Shi et al. 2007) . Since Kr-h1 is a transcription factor that regulates expression of other genes, we will now use Drosophila transgenic strains in microarray studies to identify these genes. This work is being performed by graduate student Brendon Fussnecker, and is supported by a subcontract of an NIH-NIDCD grant to Gene Robinson (UIUC).

Finally, we are beginning to address the roots of pheromone-mediated behavior in social insects. Preliminary investigations (in collaboration with Guy Bloch, Hebrew University of Jerusalem and Harland Patch, Penn State) with Kr-h1 revealed that its expression is strongly downregulated by queen presence in bumble bees. Interestingly, in both bumble bees and honey bees, queen presence/pheromone regulates worker ovary development and juvenile hormone levels (Bloch and Hefetz 1999) . Thus, Kr-h1’s ancestral role may have related to reproduction and/or hormone levels. In collaboration with DeWayne Shoemaker (USDA-ARS) and John Wang (University of Lausanne) we will develop new genomic resources for fire ants and characterize the genes and molecular processes regulated by queen pheromone in this species (these studies are supported by a USDA-NRI grant) Finally, post-doctoral researcher Amy Toth is studying the molecular bases of chemical communication and dominance hierarchies in paper wasps (these studies are supported by a USDA postdoctoral fellowship to Dr. Toth).

The effect of activation of the immune system on chemical communication.

With the sequencing of the bee genome, it has become apparent that bees have fewer immune genes than solitary insects (Evans et al. 2006) , suggesting that they use modified behavioral responses to control diseases and pests. Indeed, strains bred for resistance to Varroa mites have improved hygienic behavior, leading to reduced parasite load (ie, Harbo and Harris 2006) . We seek to characterize another behavioral response: modulation of chemical communication between diseased workers and queens and their nestmates. We have demonstrated that activation of the worker immune system alters cuticular hydrocarbon profiles and social interactions (Richard et al. submitted) . We will expand on these studies to explore the effect of different types of immune responses, and include microarray analysis to correlate changes in social interactions with gene expression differences. Thus these studies should provide insights into the molecular events associated with immune responses and the biosynthetic pathways associated with hydrocarbon production. Chemical communication of disease states has not been broadly investigated, and could have far-reaching impacts in chemical ecology and pest management. This research is funded by the USDA-NRI and is being conducted by post-doctoral associate Freddie-Jeanne Richard (now an assistant professor at University of Poitiers, France).

Relevant Publications:

Kocher, S.D., Richard, F.J., Tarpy, D.R., and C.M. Grozinger.  “Queen reproductive state modulates queen pheromone production and queen-worker interactions in honey bees” Behavioral Ecology. Advance Access published on July 2, 2009; doi: doi:10.1093/beheco/arp090

Alaux, C., Y. Le Conte, H. Heather, S. Rodrigues-Zas, C.M. Grozinger, S. Sinha, and G. E. Robinson. “Regulation of brain gene expression in honey bees by brood pheromone” Genes, Brain, and Behavior 8(3):309-19 (2009).

Richard, F.J., A. Aubert, and C.M. Grozinger. “Modulation of nestmate recognition by immune stimulation in honey bees, Apis mellifera”. BMC Biology 6:50 (2008).

Fussnecker, B. and C.M. Grozinger. “Dissecting the role of Kr-h1 brain gene expression in foraging behavior in honey bees (Apis mellifera)”. Insect Molecular Biology. 17(5):515-22 (2008).

Kocher, S.D., Richard, F.J., Tarpy, D.R., and C.M. Grozinger. “Genomic analysis of post-mating changes in the honey bee queen”. BMC Genomics. 9(1):232 (2008).

Fischer, P. and C.M. Grozinger. “Pheromonal regulation of starvation resistance in honey bee workers”. Naturwissenschaften. 95(8):723-9 (2008).

Hornstein, E.D. “Longevity in the honeybee (Apis mellifera): expression of telomerase and insulin signaling pathway genes in queen and worker bees”. Journal of Young Investigators. Vol 18. (2008) (Mentor: C.M.G.; E. Hornstein was a high school student in my lab).

Richard, F.J., Tarpy, D.R, and C.M. Grozinger. “Effects of insemination quantity on honey bee queen physiology”. PLoS ONE , 2(10):e980 (2007).

Grozinger, C.M., Fan, Y., Hoover, S.E.R. and M.L. Winston. “Genome-wide analysis reveals differences in brain gene expression patterns associated with caste and reproductive status in honey bees (Apis mellifera).” Molecular Ecology 16(22):4837-48 (2007).

Shi, L., Lin, S., Grinberg, Y., Beck, Y., Grozinger, C.M., Robinson, G.E. and T. Lee. “Roles of Drosophila Kruppel-homolog 1 in neuronal morphogenesis”. Dev Neurobiol. 67(12):1614-26 (2007).

Grozinger, C.M., Fischer, P, and J.E. Hampton. “Uncoupling primer and releaser responses to pheromone in honey bees.” Naturwissenschaften 94(5):375-9. (2007) **publication with undergraduates

Grozinger, C.M. and Robinson, G.E. “Endocrine modulation of a pheromone responsive gene in the honey bee brain” Journal of Comparative Biology A 193(4):461-70 (2007).

Honey Bee Genome Consortium (C.M.G., contributing author). “The genome of a highly social insect, the honey bee Apis mellifera.” Nature 443(7114):931-49 (2006).

Robinson, G.E., Grozinger, C.M., and Whitfield, C.W. (2005) “Social life in molecular terms.” Nat Gen Rev 6, 257-270.

Grozinger, C. M., Sharabash, N. M., Whitfield, C. W. and Robinson, G. E. (2003) “Pheromone mediated gene expression in the honey bee brain.” Proc Natl Acad Sci U S A 100 (Suppl 2),14519-25.