C3.

C3. Chemical probes for improving plant water‐use efficiency

Drought and related stresses reduce crop yields up to 50% despite the fact that over 70% of global fresh water is used in agriculture. Thus, finding practical applications for plant drought stress management is an important challenge. The plant hormone ABA, an isoprenoid derivative, prevents plant water loss by closing stomatal pores. Binding of ABA to its PYR/RCAR receptors leads to conformational change and activation of ABA downstream responses including regulation of guard cell anion channels (22). ABA signalling is highly conserved in plants and there are 14 PYR/RCARs in Arabidopsis, however, it is not yet known how individual receptors differ in specificity at guard cell level. Group 4 with Spanish collaborators (PL Rodriguez) has used various genetic approaches to define which of the PYR/RCARs are required for stomatal responses. Our unpublished data indicates that the stomatal ABA response and plant water‐use efficiency are sensitive to a certain threshold and specificity of ABA receptors. Identification of the PYR/RCAR receptors responsible for stomatal regulation by group 4, allows manipulation of plant drought resistance by identifying and synthesizing chemical probes (jointly with group 1 and 6) that are able to selectively activate guard cell ABA receptors. Several agonists for ABA receptors have already been identified, but they are either seed‐specific, activate multiple receptors or are not very efficient in crops (23). We postulate that manipulating only guard cell ABA receptors would lead to increased drought resistance while avoiding unwanted effects of ABA elsewhere in the plant, as ABA is involved in regulating different processes from seed germination and development to growth and senescence. A new generation of ABA analogues would have practical applications in drought stress management of agricultural crops.