Agrochemical control of plant water use using engineered abscisic acid receptors

Abstract

Rising temperatures and lessening fresh water supplies are threatening agricultural productivity and have motivated efforts to improve plant water use and drought tolerance. During water deficit, plants produce elevated levels of abscisic acid (ABA), which improves water consumption and stress tolerance by controlling guard cell aperture and other protective responses. One attractive strategy for controlling water use is to develop compounds that activate ABA receptors, but agonists approved for use have yet to be developed. In principle, an engineered ABA receptor that can be activated by an existing agrochemical could achieve this goal. Here we describe a variant of the ABA receptor PYRABACTIN RESISTANCE 1 (PYR1) that possesses nanomolar sensitivity to the agrochemical mandipropamid and demonstrate its efficacy for controlling ABA responses and drought tolerance in transgenic plants. Furthermore, crystallographic studies provide a mechanistic basis for its activity and demonstrate the relative ease with which the PYR1 ligand-binding pocket can be altered to accommodate new ligands. Thus, we have successfully repurposed an agrochemical for a new application using receptor engineering. We anticipate that this strategy will be applied to other plant receptors and represents a new avenue for crop improvement.

Leveraging abscisic acid receptors for efficient water use in Arabidopsis

“…ABA perception recruits an ABA-binding REGULATORY COMPONENT OF ABA RECEPTOR (RCAR)/PYRABACTIN RESISTANCE 1 (PYR1)/PYR1-LIKE (PYL) and an associated protein phosphatase of type 2C (PP2C) (18,19). Administration of ABA and ABA agonists (20,21), ectopic expression of RCARs (17,18,(22)(23)(24), as well as reduced expression of PP2Cs (25) have been shown to minimize plant transpiration and, in some cases, to enhance survival under water deficit. It is clear that plants with strongly reduced transpiration are limited in CO 2 uptake and, hence, in growth and biomass formation.…”

Plant Chemical Genetics: From Phenotype-Based Screens to Synthetic Biology

“…The fungicide mandipropamid bound with low affinity to a particular mutant that was further improved by targeted mutagenesis, resulting in a nanomolar affinity of mandipropamid in the engineered PYR1 receptor. Crucially, the conserved and essential Lys residue needed for ABA responsiveness was substituted by an Arg, rendering the engineered PYR1 receptor responsive to mandipropamid, but not to ABA, and creating an orthogonal ligand-receptor system (Park et al, 2015). In addition, because overexpression of wild-type ABA receptors results in decreased yields (Kim et al, 2014), substitution of the essential Lys residue ensured that the overexpressed engineered PYR1 failed to have negative consequences for plant growth (Park et al, 2015).…”

“…This idea was the impetus for a PYR1-focused screen involving a mutant collection covering all possible amino acid combinations for the residues lining the PYR1 ABA-binding pocket (Park et al, 2015). The fungicide mandipropamid bound with low affinity to a particular mutant that was further improved by targeted mutagenesis, resulting in a nanomolar affinity of mandipropamid in the engineered PYR1 receptor.…”

“…Crucially, the conserved and essential Lys residue needed for ABA responsiveness was substituted by an Arg, rendering the engineered PYR1 receptor responsive to mandipropamid, but not to ABA, and creating an orthogonal ligand-receptor system (Park et al, 2015). In addition, because overexpression of wild-type ABA receptors results in decreased yields (Kim et al, 2014), substitution of the essential Lys residue ensured that the overexpressed engineered PYR1 failed to have negative consequences for plant growth (Park et al, 2015). Orthogonal receptorligand pairs are designed to become unresponsive to endogenous signaling cues, such as ABA in the case of the engineered PYR1 receptor (Fig.…”

The spatio-temporal specificity of PYR1/PYL/RCAR ABA receptors in response to developmental and environmental cues

“…[3][4] Given the dimeric receptors show a higher dissociation constant for ABA (greater than 50 mM; lower affinity) than monomeric ones (approximately 1mM), the endogenous ABA level determined the selection for this two types receptor sub-families. 38 According to the literatures, it is proposed that the dimeric receptors act as the key targets for chemical modulation of vegetative ABA responses as well as the objective receptors for protein engineering, [5][6]39 while the monomeric ones prefer implicated in genetic-modify plant traits for abiotic stress tolerance 2 and also involved in root function regulation. [17][18]23 That the more sensitive of shoot growth than root growth in response to draft stress, is resulted from the insufficient ABA level in the former than the latter to restrict ethylene production.…”