Scientists have long been captivated by flowers' capacity to replicate the sexually appealing characteristics of pollinators in order to get them to drink their nectar.
Flowers cannot buy glasses and wigs to disguise themselves. So how they managed to produce such convincing dupes with only an existing DNA toolset is perplexing.
Flowers Mimicking Insects
Orchids are the most notorious flower for insect mimicry and can appear and smell seductive to an unwary insect, Science Alert reported. Its brief visits amid the petals leave the insect loaded with pollen from the Orchid, which eventually travels to other flowers.
These flowers evolved this attribute so long ago and with a such overpowering success that all individuals without these qualities have long since vanished.
But aside from orchids, other flowers are also known to display this characteristic. So, scientists went on to study the South African daisy Gorteria diffusa, whose sexual mimicry arose very recently in evolutionary history and is not uniform among the species' blooms.
The petals of this daisy range in color from pale yellow to vivid red-orange, with some having dots that create a circle around the flower's center. These flowers vary widely in appearance in which some would have dots turned into green-black lumps that seem just like a fly's female partner, hanging seductively atop the petals.
Researchers recently traced the evolution of this species' diverse properties in order to establish the sequence in which the qualities developed to end in such a convincing deception: it showed color first, then random location, and last texture.
Evolutionary biologist Roman Kellenberger from the University of Cambridge led the new study, titled "Multiple gene co-options underlie the rapid evolution of sexually deceptive flowers in Gorteria diffusa," which was published in the journal Current Biology.
Genetics Behind Insect Mimicry of Flowers
The new research investigates how three sets of genes that had once nothing to do with appealing to flies have become part of this mechanism to attract pollinators.
Plant biologist Beverley Glover from the University of Cambridge and the senior author of the study said in the press release via EurekAlert! that the daisy did not evolve to make a fly gene, rather it brought existing genes to make a complicated spot on the petals that deceive male flies.
As Science Alert reported, one of these genes transports iron across the plant, while another causes root hairs to develop, and a third determines when flowers are produced.
The iron-moving genes generate patches that direct pollinators to the nectar reward, a tried-and-true pollination tactic flowers used long before sexual mimicry emerged. The resultant pigments produce a blue-green-black tint, which is the precise color of a fly's carapace.
Then, a set of genes involved in flower formation were repurposed as an "off switch" for the nectar-guiding patches, causing the 'fake flies' to arrive in seemingly random areas on the petals.
The gene sequence normally associated with the formation of a plant's root hairs is crucial for truly bringing the dupe to life, resulting in the 3D shapes and textures of the fly-like petal patches on the daisy.
EXPA, the protein produced by this gene, relaxes the normally hard plant cell walls, resulting in "irreversible cell expansion." This protein causes the existing hairs in the petal to extend, providing surface texture.
This gene was nearly completely inactive in growing leaves and unspotted florets, moderately expressed in developing roots, and substantially expressed in developing spotted flowers. Bringing these three genes together has created an evolutionary shortcut for these flowers, the masters of disguise.
RELATED ARTICLE: Flowers' Unseen Substance, A 'Bulls-Eye' for Pollinators: How Chemical Changes in Plants Help With Pollination
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