Published in Nature, researchers from Aarhus University and the Technical University of Munich used Diamond’s eBIC facility to uncover new insights into what drives movement in plants.
Auxins are hormones playing a central role and controlling nearly all aspects of plant growth and development. Charles Darwin observed that plants could grow directionally in response to environmental stimuli such as light or gravity. In his book, The Power of Movement in Plants, published in 1880, Darwin showed that the part of the plant responding to such a stimulus differs from the part that perceives it. He proposed that some kind of ‘influence’ must travel from the perception site to the response area. However, Darwin was unable to identify the influence.
Darwin’s ‘growth accelerating substance’ was identified in 1926 as the hormone auxin. Later research identified that auxin is the growth factor that determines almost all plant responses to environmental changes. Directional transport of the auxin molecule between cells is required to ensure that the auxin response occurs in the correct part of the plant.
It wasn’t until the 1990s that scientists identified the proteins involved in the process. PIN-FORMED (PIN) proteins are auxin transporters, and they are essential for the development of auxin gradients within plant tissues that guide plant growth. They’re named from the distinct needle-like ‘pin’ form, without shoots or flowers, into which plants with dysfunctional PIN proteins grow. Even then, how PIN proteins fold, how they recognise substrates and inhibitors and the molecular mechanism behind transport have remained unknown.
Now researchers from Aarhus University and the Technical University of Munich have used single particle cryo-EM at eBIC to provide the first structural basis of auxin transport by PIN proteins.
Read more on Diamond website
Image: PIN8 is a 40 kDa membrane protein that transports the plant hormone Auxin. It forms a homodimer with each monomer containing two domains: transporter (green) and scaffold (blue). In the transporter domain a distinct crossover (red) is localized at the middle of the membrane plane that defines the auxin binding site. Below the structure are show 8 representative 2D classes from the data collected at eBIC that resulted in 3 distinct conformations solved. To the left are shown a schematic of the transport of Auxin (IAA) with two key conformations coloured that summarizes the transport mechanism as described by the data obtained at eBIC.