Why is it that the plant hormone auxin does something different in one place than in another?

Auxin is a simple, but powerful hormone. It controls a large number of growth mechanisms in plants, depending on where it accumulates. Dolf Weijers, professor of Biochemistry of Plant Development at Wageningen University, is trying to find out what causes this multifunctionality and how it works. He received a Vici grant worth 1,5 million euros for this research.

Multifunctional hormone unraveled
The hormone auxin is a molecular master regulator. Dolf Weijers has been fascinated by it for years. “The hormone does an awful lot of different things in plants. It determines whether a root will grow somewhere, a flower will develop or whether new vessels for the flow of sap will be created. This has been known for almost a hundred years. But one crucial question has never been answered: why is it that auxin in plants does this in one place and that in another?”

Linking protein and DNA
R2D2 root: Cells in which the nucleus glows yellow (green + red) have little auxin. The more the cell nuclei glow red, the more auxin
From the moment the hormone is recognized by the plant, auxin initiates various mechanisms, Weijers explains. “The final step is to activate proteins that bind to the plant's DNA. We call these proteins transcription factors. When activated by auxin, these transcription factors determine which of the approximately 30.000 plant genes are turned on and off. Most plant species have more than 20 different transcription factors. What is crucial is which of these factors are present in a plant cell. Because depending on that, auxin activates one process or the other.”

Functioning of transcription factors
Weijers wants to understand how these different transcription factors ensure that other genes are turned on. Ultimately, he wants to understand how the range of auxin functions arose during the evolution of plants. Thanks to the Vici grant, he can now put together a team of five researchers who will together delve into the evolution of the plant. “We first collect information from the 1000 Plant Genome Project. From this we will find out which transcription factors are present in which plant species, from single-celled algae to trees. In this way we want to trace back what evolution has caused all kinds of different variants to arise. We then go into the lab, where we do tests based on predictions. We want to unravel why auxin does its specific work at key positions in plants.”

Dialogue with plant breeders in the business community
The research project has a duration of five years. During that period, Weijers wants to conduct an intensive dialogue with people from the business community, such as plant breeders. “You can imagine that it is very interesting for those companies to learn more about the effect of auxin in plants. Especially if we find out how we can gain more control over it. It would be fantastic for breeders if this knowledge could be used to further improve existing breeding procedures.”

Source: https://www.wur.nl/nl/nieuws/hoe-komt-het-dat-het-plantenhormoon-auxine-op-de-ene-plek-iets-anders-doet-dan-op-de-andere.htm