Potsdam Study Finds 2-Factor Supergene Drives Mirror-Image Wachendorfia Flowers

Q: Why do these unique flowers rely on gravity to tell left from right when animals use internal genetic cues?

These flowers rely on gravity because, unlike animals, they do not set left and right from a fixed internal body plan. In *Wachendorfia*, the developing flower uses an external reference — up versus down — to orient its reproductive organs, and gravity provides that cue. The study shows that genes alone do not physically place the style and stamens. A tightly linked supergene determines whether a flower follows the left-handed or right-handed version of the pattern, but the organs reach their final positions through movement during development. The style rotates early, then continues growing asymmetrically, and that later growth is guided by gravity. Depending on the genetic form, gravity-biased growth pushes the organ left or right from the floral midline. Animals typically establish left-right asymmetry inside the embryo through inherited molecular signals tied to stable body axes such as head-tail and back-belly. A flower is different: it is a lateral organ produced on a plant body that can orient itself in relation to the outside world. In this case, the plant appears to use gravity as the dependable directional landmark needed to convert a genetic program into precise mirror-image architecture. That arrangement has a clear payoff. By placing pollen and stigma on opposite sides in complementary left- and right-handed flowers, *Wachendorfia* improves cross-pollination, limits self-pollination and may even help drive reproductive isolation over time.

2 articles · Updated · BIOENGINEER.ORG · Aug 1

A Science study traced Wachendorfia’s left- or right-bending reproductive organs to a supergene with two major linked factors that separately control stamen and style orientation.
That tight linkage keeps both organs aligned into two mirror-image floral forms, directing pollen onto matching parts of pollinators and reinforcing cross-pollination over selfing.
Experiments on Wachendorfia thyrsiflora showed the styles first rotate, then keep growing asymmetrically under gravity, with both steps required to produce the mature left-right pattern.
The finding resolves a century-old botanical puzzle and highlights how supergenes can preserve coordinated traits that shape pollination, genetic diversity and potentially speciation.