Siri-Christine Seehuus disputerte 16. mars 2006

Ane Skjelfjord

The yolk precursor protein vitellogenin has several characteristics linking it to regulation of lifespan in honey bees. Aging in the honey bee seems to have similar pathophysiology as aging in other species. Thus, aspects of these mechanisms may well prove to have general interest as a model system for senescence related diseases.

Animal model on social terms - The honey bee (Apis Mellifera)

Reproductive protein protects worker honey bees from oxidative stress
The aims of this study was built on assumptions on the role of the egg precursor protein vitellogenin in the honey bee worker. In the honey bee (Apis mellifera), vitellogenin is produced by the reproductive queen caste. However, it is also produced by the facultatively sterile female worker caste where it appears to have been remodelled to promote longevity. By use of various imaging techniques we wanted to further understand the role of vitellogenin dynamics in the honey bee worker. In the three first papers we were able to test specific hypothesis on vitellogenin function. The first hypothesis was based on the assumption that vitellogenin promotes longevity by functioning as an antioxidant. We established that vitellogenin gene activity protected worker bees from oxidative stress by use of the model compound paraquat and RNA interference.

Unconventional functions
Honey bee vitellogenin appears to have evolved functions in the sterile workers that have not been documented in other species. To further reveal the role of vitellogenin in honey bee workers we developed an immuno labelling procedure. This procedure opened up for a deeper understanding of the unconventional functions of a reproductive protein in the honey bee worker. The protocol enabled us to prove the presence of vitellogenin in hypopharyngeal (brood food producing) glands of nursing honey bee workers. Thus, we were able to set to rest conflicting hypothesis regarding the role of vitellogenin in alloparental care taking.

Age – governed by social role?
The different temporal worker phenotypes have different lifetime expectancies where long lived phenotypes are characterised by high vitellogenin levels. Accumulated oxidative damage with chronological age is one of the hallmarks of senescence in vertebrate and invertebrate species used in aging research. Knowledge about the intrinsic aging machinery of the worker honey bee is sparse and in our third paper we hypothesised that long lived worker phenotypes aged at slower rates than shorter lived phenotypes. We were able to show by use of immunohistochemical methods that accrual of oxidative carbonylation damage in the honey bee brain was comparable between workers within the same temporal phenotype. The results indicate that brain senescence in the honey bee is coupled to physiological phenotype rather than chronological age.

The honey bee colony as a model system
The three first studies focused on the physiology of the different worker phenotypes, whereas our fourth study focused on the honey bee society at colony level. The honey bee colony unit can be viewed as a superorganism, with complex survival strategies much like multicellular organisms. The colony survives and creates order through surveillance systems and social cues that influence the individual bee's behaviour. This order can fail if the surveying parts become too few or individuals trick the system. This faillure can in some cases lead to disease or even death of the colony unit. This review paper is a first attempt to introduce the honey bee to the field of cancer research. At the interface of order, disorder and disease the honey bee colony may well function as a model system in medical research.

This thesis work is a contribution to further reveal the role of the egg yolk precursor protein vitellogenin in the honey bee worker. The surmised role in both regulation of aging and alloparental care taking has been substantiated and the honey bee emerges as a model for research in the pathophysiology of aging and disease.

Key words / ISI database key words:
aging, social evolution, vitellogenin, carbonylation, RNA interference, honey bee, worker ovary, immunohistochemistry, immunogold labeling, oxidative stress, brain senescence, stage dependent aging


Nøkkelord til artikkelsøk: aldring, sosial utvikling, vitellogenin, karbonylering, RNA-interferens, honningbie, arbeider bie, arbeider ovarier, immunohistokjemi, immuno gull merking, oksidativt stress, aldring av hjernen, sosial rolle og aldringsregulering

Address as from april 2006:
UMB, IHA, Postboks 5003, 1432 Ås



Oppdatert: 21.09.06
Utskriftsvennlig versjon : Arkiv : Tips en venn