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You are here: Research & Tech Bee Behaviour Mitochondrial Proteins Cause Queen and Worker Bee Differentiation

Mitochondrial Proteins Cause Queen and Worker Bee Differentiation

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Pune, September 25, 2011: One of the much studied subjects in honey bee biology is the difference in growth of larvae of queen and worker bees, though developing from fertilized eggs with the same genetic constitution. It is known that the female young larvae destined to become queen bees, get a protein-rich and biologically active royal jelly, while those developing into worker bees get a poorer diet.

A recent study by Begna and colleagues from the Key Laboratory of Pollinating Insect Biology, Beijing, China provided an insight into the mitochondrial proteins associated with regulatory mechanism of caste differentiation. Their findings* published in the latest issue of the Journal of Proteome Research reveal major differences, during early stages of life, in the amounts and activity of proteins in the mitochondria. "This suggests proteins with metabolic enhancing activities generally appear to have significant roles in the process of caste differentiation," the researchers conclude.

Following is reproduced from the Press release dated September 21, 2011 by the American Chemical Society, the publishers of the Journal of Proteome Research, followed by the Abstract of the paper.

*Reference cited: Begna, D., Fang, Y., Feng, M. and Li, J. 2011. Mitochondrial proteins differential expression during honey bee (Apis mellifera L.) queen and worker larvae caste determination. Journal of Proteome Research 10 (9): 4263 - 4280.

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AMERICAN CHEMICAL SOCIETY, ACS News Service Weekly PressPac: September 21, 2011

Queen bee or worker bee? New insights into famous honeybee society caste system

"Mitrochondrial Proteins Differential Expression during Honeybee (Apis mellifera L.) Queen and Worker Larvae Caste Determination" - Journal of Proteome Research

Scientists are reporting deep new insights into whys and hows of the famous caste system that dominates honey bee societies, with a select few bee larvae destined for royalty and the masses for worker status. Their study probing the innermost biological makings of queen bees and worker bees appears in ACS's Journal of Proteome Research.

Jianke Li and colleagues (The joint work of scientists from China and Ethiopia) note that despite more than a century of research, mysteries remain about the biochemical factors at the basis of the fascinating caste system in honeybee colonies. School children learn tha the (usually) one queen bee in a colony develops from larvae fed royal jelly, a protein-rich secretion from glands on the heads of worker bees. Other larvae develop into female workers or male drones. Although queen and worker bees share almost identical genes, their destinies could be more different. "The female queen is large in size and specializes in reproduction," the scientists explain, "whereas workers are small and engage in colony-maintaining activities. Their life spans also vary, with the queen living for 1 to 2 years and the workers livng only 6 to 7 weeks. To gain further information, the scientists looked at proteins inside the cells of larvae destined for queen and worker status.

Their findings reveal major differences, during early stages of life, in the activity of proteins in the mitochondria, structures that produce energy for cells. The differences include changes in the amounts of protein produced in cells and the activity of those proteins. In pre-queen larvae, proteins involved in carbohydrate and energy metabolism, for instance, are  much more active than in workers. "This suggests proteins with metabolic enhancing activities generally appear to have significant roles in the process of caste determination," the researchers conclude.

The authors acknowledge funding from Modern Agro-industry, Technology Research System and The National Natural Science Foundation of China.

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Abstract

Despite their similar genetic makeup, honeybee (A. mellifera) queens and workers show alternative morphologies driven by nutritional difference during the larval stage. Although much research have been done to investigate the cases of honeybee caste polymorphism, information at subcellular protein levels is limited. We analyzed queen- and worker-destined larvae mitrochondrial proteome at three early developmental stages using combinations of differential centrifugation, two-dimensional electrophoresis, mass spectrometry, bioinformatics, and quantitative real time PCR. In total, 67, 69, and 97 protein spots were reproducibly identified as mitochondrial proteins at 72, 96, and 120 h, respectively. There were significant qualitative and quantitative protein expression differences between the two castes at three developmental stages. In general, the queen-destined larvae up-regulated large proportions of proteins at all of the developmental stages and, in particular, 95% at 72 h. An overwhelming majority of the queen larvae up-regulated proteins were physiometabolic-enriched proteins (metabolism of carbohydrate and energy, aminoacid, and fatty acid) and involved in protein folding, and this was further verified by functional enrichment and bilogical interaction network analyses as a direct link with metabolic rates and cellular responses to hormones. Although wide-ranging mitochondrial proteomes participate to shape the metabolic, physiologic, and anatomic differences between the two castes at 72 h, physiometabolic-enriched proteins were found as the major modulators of the profound marking of this caste differentiation. Owing to nutritional difference, prospecitve queen larvae showed enhanced growth, and this was manifested through the overexpression of metabolic enzymes. Differently from similar studies targeting the causes of honeybee caste polymorphism, this subcellular level study provides an in-depth insight into mitochondrial proteins-mediated caste polymorphism and greatly improves protein coverage involved during honeybee caste determination. Hence, it is a major step forward in the analysis of the fundamental causes of honeybee caste pathway decision and greatly contributes to the knowledge of honeybee biology. In particular, the consistency between the 22 proteins and mRNA expressions provides us important target genes for the reverse genetic analysis of caste pathway modulation through RNA interference.