It was once assumed that the difference between queen and worker development had to do with the _amount_ of royal jelly the larvae are fed. Then, speculation was on the difference in the nutritional content. Now we see that there are components to the food fed to larvae and also adults that can regulate gene expression. One of the key components appears to be an insulin like substance. This new information is embedded in recent papers that do not have widespread distribution in the beekeeping community so it is natural that the ideas may take time to catch on. However, we are at the beginning of a new era of understanding of how genetic information is controlled in living organisms that have already gone through the developmental stages.

* * *

Insulin/insulin-like growth factor signaling (IIS) regulates longevity in animals (127). In honey
bees, IIS may mediate the effects of royal jelly in modulating alteration of epigenetic status in larvae,
given that royal jelly regulates IIS and IIS regulates DNA methylation and histone modifications
in mammals (42, 91, 109). In honey bee adults, queens have less IIS activity than workers (26) and
nurses have less IIS activity than foragers (5), consistent with the observation that reduction of IIS
signaling extends life span in other animals.

Studies of the dynamic regulatory functions of gene body methylation underscore a new paradigm
for understanding the role of epigenetic machinery in regulating behavior and longevity. DNA
methylation–mediated alternative splicing in humans and in eusocial insects suggests that dynamic
expression of splicing variants may be utilized to interpret the environmental signals and express
variable phenotypes. Interconnected phenotypes in reproduction, behavior, and longevity in eusocial
insects provide a unique model to understand how tissue-specific DNA methylation responds
to internal and external factors and how cross talk between different tissues regulates epigenetic
status in the organism.

Our understanding of gene body methylation and its potential epigenetic functions is still in
its infancy. Further investigations should address the following questions: How does the interplay
between gene body methylation and other epigenetic modifications achieve persistent phenotypic
states while maintaining their plasticity? How do epigenetic signals in different tissues (e.g., brain,
fat body, ovary) interact to establish, maintain, and alter the behavioral response to environmental
factors? What is the genetic and epigenetic basis of the strong connection between reproduction,
behavior, and life span in eusocial insects?  -- Annu. Rev. Entomol. 2015. 60:23.1–23.18

* * *

Additional comment:

The series of questions at the end points out what some of the implications are. Plasticity refers to the fact that these so called epigenetic changes can be reversed as needed, so that alternate gene expression can be turned on or off on an as-needed basis. Obviously, a honey bee worker cannot become a queen but in some other social insects, the difference is not so clear. Some wasps can become queens when the founding queen dies. A lot of these underlying mechanisms are shared by various bees, wasps and ants. I realize that some of this may not have any bearing on beekeeping, per se, but if you are called upon (like I am) to talk about bee biology, it is worth incorporating new discoveries into what we teach. For example, we can ditch the old idea that bees wear themselves out on the honey flow, now that we see that lifespan is regulated by biochemical means. Also, bee researchers are at the forefront of understanding how lifespan is controlled in other organisms. 

PLB

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