Beebread and Jelly: How a Bee's Diet Determines Caste

Imagine this: You're enjoying your midday meal when you have a startling epiphany. Suddenly you just know what it is you're meant to do in life. What's more, your body starts to change to fill that role! It's not something that happens everyday for us humans, but for bees, it's a regular part of life.

That's at least according to a study recently published in the journal Science Advances, which details how a bees daily meal heavily influences their lot in life, including caste and physical development.

"Consuming [plant chemicals], which is ubiquitous in beebread and honey, alters the expression of a whole suite of genes involved in caste determination," entomologist May Berenbaum, who conducted the study with research scientist Wenfu Mao and developmental biologist Mary Schuler, said in a statement.

In a traditional beehive, it seems like the larvae destined to be strong workers (sterile females) are given the heartiest meals - packed full of not only processed pollen, called 'beebread,' but also a substance known as 'royal jelly.' (Scroll to read on...)

This jelly, which is secreted by adult worker bees, is valued in many countries as a growth and fertility supplement. The traditional thought is that because larvae destined to be queens are exclusively fed royal jelly (no beebread for royalty!), it must contain powerful nutrients.

However, experts have long known that this mysterious milky substance is largely just water and sugar, and contains only one key ingredient - trace amount of a protein commonly called "royalactin," which somehow influences queen growth. A study published in the journal Nature only four years ago finally verified this theory, when it was revealed that royal jelly lacking royalactin cannot make a queen.

What Berenbaum wondered is, if workers are fed royal jelly too (albeit smaller quantities), why do they not also become queens?

"For years, people have wondered what components in royal jelly lead to queen development," Berenbaum said, "but what might be more important is what isn't in royal jelly."

That pointed the researcher and her colleagues to beebread, and there they found their answer. Carefully examining the genes of larvae switched from a pure royal jelly diet to jelly and beebread, the trio found that plant chemicals (phytochemical p-coumaric acid) found in beebread and honey actually interfere with the path to queen development. Specifically, about a third of the honeybee genome is "upregulated" to make a strong worker, while another third are downregulated, changing the landscape of proteins available to help fight disease or develop the bees' reproductive parts.

In this way, it's safe to say that bees are not only what they eat, but also what they don't. Yes, royal jelly is undeniably essential to queen growth. 'Princess' larvae are nearly drowned in the stuff! However, tainting a royal meal with the bread of a commoner... that's just unforgiveable.

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