Imagine – you have just been born and your future looks bleak. You have been cared for only the first days after birth and then you are already forced to work: cleaning the home that you share with your many siblings, collecting food not for yourself but for the community, keeping watch and defending your home with your life, if necessary.
You will not have a single minute of free time and never go on vacation. You will age fast and within a few weeks you have worked yourself to death. And the worst part – you will never have known true love. How different is the life of your sister. She will be pampered, she never has to leave home, she will be surrounded by loyal servants, who feed her, clean her and protect her. She exceeds you in weight and size, she has many lovers and she will be mother to thousands of offspring. Your sister is more resistant to environmental stress factors, ages much more slowly and will live 10 times longer than you. She has nothing to fear – because she is the queen and you are just a common worker bee.
One genome – two fates
The honeybee (Apis mellifera) forms two female castes: the queen and the worker. While the queen bee is large in size and specialised in reproduction, the workers are small and engaged in activities for maintaining the colony. The queen bee lives far longer than any other bee in the hive. She is more resilient with respect to extrinsic environmental stress factors, such as thermal stress and has a slower intrinsic ageing process in comparison to worker bees.1 Despite their vastly different appearance, physiology and behaviour, queen and worker bees share the same genome. They differ only in which genes are activated and hence which proteins are produced to serve specific functions. Indeed, young queen larvae produce higher levels of proteins involved in amino acid metabolisation, energy production and repair, a prerequisite for tissue growth and maintained homeostasis. How does it work? Honeybees modify their genetic code by consuming a special diet called royal jelly (RJ). This peculiar juice leaves chemical ‘markers’ on the DNA, which modify gene expression without actually changing the genetic code – a process referred to as ‘epigenetic’ modification (‘on top of the genome’). Thus, honeybees have a clever way of generating two contrasting organisms by using environmental factors to influence the same genome. RJ is the epigenetic trigger that determines a honeybee larvae’s fate.
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