Engineered ABA receptors and drought tolerance

One of the biggest developments in plant biology of recent years is the discovery of receptors for the main plant growth regulators. Abscisic acid (ABA) has been known to regulate drought responses since the 1960s, yet its receptor was only identified in 2009. The discovery of the PYRABACTIN (PYR) receptors has revolutionised our understanding of ABA signalling, and a huge amount of work has been done since then to characterise the pathways downstream of ABA at a molecular level.

Dr Sean Cutler’s group at US Riverside has recently published a paper demonstrating that the PYR1 receptor can be engineered to allow chemical control of drought responses. They first created a series of mutant versions of PYR1, mutating residues around the ligand binding site. They then screened these mutant PYRs to identify ones that responded to a range of different chemicals. After isolating a candidate mutant, and then further mutating it to increase responsiveness, the researchers developed PYRMANDI, which has high sensitivity to the chemical mandipropamid.

PYRMANDI plants sprayed with mandi have higher leaf temperatures. Image © Nature.
PYRMANDI plants sprayed with mandipropamid have higher leaf temperatures. Image © Nature.

The researchers then overexpressed PYRMANDI in both Arabidopsis thaliana and tomato plants. When the PYRMANDI plants were sprayed with mandipropamid, thermal imaging showed that the plants had elevated temperatures compared to the controls, indicating the stomata had closed and evapotranspiration was blocked (see previous post for more thermal imaging data in stomatal research). The PYRMANDI plants sprayed with mandipropamid were also better able to withstand dehydration than control plants.

This proof-of-concept experiment is only the first stage in developing a drought tolerant crop. However it is a nice demonstration of how knowledge of the fundamental biology can be translated into potentially useful agronomical traits.

Reference: Park et al. (2015) Agrochemical control of plant water use using engineered abscisic acid receptors. Nature. DOI:10.1038/nature14123

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