Researchers at UC Berkeley and the University of Connecticut discovered the genetic programming behind the monkeyflower’s intricate, patterned spots.

The findings, published in the journal Current Biology on Feb. 20, use genetic tools to explain the process by which the pigmented spots act as “bee landing pads,” attracting bees and guiding them to enter the flower to get the sweet nectar.

“We know a lot about how pigments are made, but we know a lot less about how these patterns are painted onto petals,” said campus assistant professor of plant and microbial biology Benjamin Blackman. “They often lead to interactions with pollinators, attracting and orienting them as they approach the flower.”

Having grown up collecting monkeyflowers, Blackman served as one of the two senior authors of the study. As he collected monkeyflowers throughout California and Oregon, he measured their traits.

During this time, Blackman noticed certain flowers had large patches of pigment on their petals, instead of characteristic red spots dappling their throats. This variety is called the red tongue, as it looks like the plant is “sticking its tongue out.”

The Blackman Lab collaborated with the Yuan Laboratory at the University of Connecticut, which is run by associate biology professor Yaowu Yuan.

Both labs discovered the gene independently but decided to pool their resources. The Yuan Laboratory focused on how the gene acts within cells, while the Blackman Lab examined how often this occurs in natural populations.

“While this sort of collaborative work between two labs can be frustrating, in this particular case it was really fun,” Yuan said. “It made the story that much more strong and impactful.”

Over the course of about six years, they found that the monkeyflower’s pigmentation follows an activator-repressor system.

In the circuit system, an activator molecule known as nectar guide anthocyanin stimulates a cell that produces the red-colored pigment, creating a spot. Simultaneously, a repressor molecule is sent to surrounding cells to prevent them from producing the red pigment.

Using CRISPR and other technologies, the researchers pinpointed the inhibitor gene.

More specifically, campus postdoctoral researcher Srinidhi Holalu identified two natural varieties of the yellow monkeyflower and genetically transformed them.

Blackman said the primary takeaway is that bees seem to prefer different patterns. Having various forms of small spots as opposed to bigger, blotchy spots can be less or more attractive to bees.

These observations, however, were made under laboratory conditions, and wild bees may learn and adapt beyond their innate preferences. Nevertheless, these preferences in “naive bees” suggest a possible reason as to why the red tongue persists in natural populations.

“Studying organisms, even if they don’t have immediate economic or health benefits towards regular people, provides us with such intellectual, satisfying explanations to biological systems,” Yuan said. “It gives us an entry point to investigate other unique and beautiful patterns of many varieties.”