BEHAVIOUR AND BEE BRAINS

Abstract

The question of whether there are links between our genetic makeup and the way we behave has long puzzled humans. With the publication of the human genome we may finally be on the verge of answering this tantalising question. Some scientists hope ultimately to be able to predict behaviour by simply looking at our genetic makeup. Unfortunately, humans are probably too complex to begin answering this problem at the moment. However, undaunted by the enormity of the task, Charles Whitfield and his colleagues at the University of Illinois have set about tackling the problem, while setting their sights a little lower. They have turned their attention to a relatively simple creature, the honey bee (Apis mellifera), to start unravelling how(and if) our genes control what we do.Bees are fascinating because they form complex societies, where everyone has a particular role. For example, worker bees have two distinct forms of behaviour. During the first 2–3 weeks of adult life, female worker bees are confined to the hive, nursing and caring for the demanding young. As they mature, they switch roles and begin foraging, spreading their wings and flying far afield to search for pollen and nectar. The change from nurse to forager depends on the number of hungry mouths there are to feed and the needs of the colony, so the team decided to look at the bee's genetic brain profiles as they switched from one behaviour to the other.Comparing gene expression patterns across 40% of the genome, the team looked at 5–9-day-old nurses and 28–32-day-old foragers from a typical colony. There were significant differences in brain gene expression for 39% of the genes in the portion of the genome tested. The team then wanted to find out whether these differences were associated with the age of the bees or with the way the bees were behaving. Whitfield and his colleagues turned their attention to single cohort colonies, where all the worker bees are the same age. In these colonies, some bees begin foraging at a very early age in the absence of older bees, while others remain in their nursing role as there are no youngsters to replace them. Knowing that all of these bees were the same age, regardless of their roles, the team measured gene activity in the brains of young and old nurses and precocious and old foragers to see whether the brain expression patterns were due to old age or experience.What they found was that there is a strong relationship between behaviour and brain gene expression; so it is not how old you are, but what you are doing that is important if you are a bee. Having shown that there is a molecular signature, like a fingerprint, that is strongly related to behaviour, the team were able to identify individual's activities from their molecular fingerprint alone, distinguishing nurses from foragers with a 92–95% accuracy! And with the publication of the honey bee genome pending, Whitfield and his colleagues are optimistic they can unravel the complex web of genetic interactions that transform bees from caring nurses to roaming foragers.