Plants warning you for dangerous substances
What if a plant can tell you that there are dangerous chemicals in the water or the ground? Not by dying but through simply changing its appearance. Now researchers from University of California – Riverside report in Nature Chemical Biology to have done just that.
Organisms are full of biosensors, they use them to respond to a changing environment. Regardless if this environment is the big outside world, or just the other cells within an organism. One of those biosensors is the sensor that plants use to respond to the plant hormone abscisic acid, or ABA. This hormone is involved in a myriad of developmental processes, like germination and regulating stomata opening.
The nice thing about the ABA biosensor and biosensors like it, is that they consist out of multiple parts. A part for sensing a ligand (like ABA). And a part that activates the targets, but only when bound to the ligand sensing part, which in turn only binds the target activating part when bound to the ligand.
Previously the researchers reported that they could adjust the ligand binding part of the ABA biosensor so that it could bind other ligands. In plants however, this had one big back drawback: it messed up with the ABA signalling.
The plants turn beet red upon sensing a banned pesticide
To overcome that they went to a couple of rounds of engineering. First to develop a ligand sensing and a target activating parts that did not bind to the original biosensor parts. This was followed up so the adjusted biosensor parts could bind to each other. Ending up with a second ABA biosensor that functioned independently from the original ABA biosensor.
Starting with this second biosensor they then adjusted it so that it could bind to either azinphos-ethyl and diazinon, both forbidden pesticides, instead of ABA. The result: two biosensors that could bind the banned pesticides in nanomolar quantities. After placing them in plants, the researchers saw no growth defects. Confirming that they indeed function independently from the original ABA biosensor.
The last step to developing a plant that could tell us if it sensed either of the banned pesticides was adding a target. For this they chose the synthetic betalain pigment gene named RUBY. This RUBY when activated produces a pigment that colours the plant beet red.
The resulted plants turn beet red upon sensing a banned pesticide. While at the same time the biosensor does not interfere with the plants own metabolism. A major feat as previously biosensors based on plant receptors messed up the plants ability to develop normally.
Literature
Park, SY., Qiu, J., Wei, S. et al. An orthogonalized PYR1-based CID module with reprogrammable ligand-binding specificity. Nat Chem Biol (2023). https://doi.org/10.1038/s41589-023-01447-7
Plant en Zo 