Sweet duplication
Some flowers have a specific hollow outgrowth wherein they store their nectar, a so called nectar spur. How these evolved is often a mystery. Now Colombian researchers show in the journal Annals of Botany that it might be the result of a gene duplication.
Flowers of Tropaeolum longifolium can only be divided in one way. They have clear left, right, top, and bottom side. The cause of this symmetry is the nectar spur that is sitting at the underside of the flower. Only it was unclear how the plant regulates the development of this nectar spur.
To find out the researchers decided to study which genes are turned on during the formation of the nectar spur. The noticed a duplicated gen, TCP4L1 and TCP4L2, was turned on early during flower development. Whereby both genes were turned on in overlapping places of the developing flower.
Duplication of TCP4 created the possibility for developing nectar spurs
That is up to when the moment comes to grow the nectar spur. At the side of the future nectar spur only TCP4L2 is turned on, not TCP4L1. Although the researchers observed that at later stages of nectar spur development TCP4L1 could be found to be turned on in parts of the nectar spur. But not at the side of nectar production, there only TCP4L2 was turned on. Both TCP4L1 and TCP4L2 are gene on/off switches. The fact that TCP4L2 is turned on during the development of the nectar spur suggests that this gene turns on the genes required for the development of nectar spurs.
To check that this gene duplication is really responsible for the development of nectar spurs, the researchers analysed the number of TCP4 copies in other plants. Noticeable was the fact that plants that formed flowers with nectar spurs had two copies of TCP4. While plants that formed flowers without nectar spurs only had one TCP4 copy.
It appears that the duplication of TCP4 in Tropaeolum longifolium created the space for nectar spur development. Although more research is needed to unravel how TCP4 is regulating nectar spur development.
Literature
Sebastián Martínez-Salazar, Elena M Kramer, Favio González, Natalia Pabón-Mora, (2023) Spatio-temporal expression of candidate genes for nectar spur development in Tropaeolum (Tropaeolaceae: Brassicales), Annals of Botany, mcad164, https://doi.org/10.1093/aob/mcad164
Plant en Zo 