An ABA-mimicking ligand that reduces water loss and promotes drought resistance in plants

Abstract

Abscisic acid (ABA) is the most important hormone for plants to resist drought and other abiotic stresses. ABA binds directly to the PYR/PYL family of ABA receptors, resulting in inhibition of type 2C phosphatases (PP2C) and activation of downstream ABA signaling. It is envisioned that intervention of ABA signaling by small molecules could help plants to overcome abiotic stresses such as drought, cold and soil salinity. However, chemical instability and rapid catabolism by plant enzymes limit the practical application of ABA itself. Here we report the identification of a small molecule ABA mimic (AM1) that acts as a potent activator of multiple members of the family of ABA receptors. In Arabidopsis, AM1 activates a gene network that is highly similar to that induced by ABA. Treatments with AM1 inhibit seed germination, prevent leaf water loss, and promote drought resistance. We solved the crystal structure of AM1 in complex with the PYL2 ABA receptor and the HAB1 PP2C, which revealed that AM1 mediates a gate-latch-lock interacting network, a structural feature that is conserved in the ABA-bound receptor/PP2C complex. Together, these results demonstrate that a single small molecule ABA mimic can activate multiple ABA receptors and protect plants from water loss and drought stress. Moreover, the AM1 complex crystal structure provides a structural basis for designing the next generation of ABA-mimicking small molecules.

ABA receptor PYL9 promotes drought resistance and leaf senescence

“…The delayed wilting and drying in pRD29A::PYL9 transgenic plants was correlated with a reduction in water loss from the soil, indicating a reduction in transpiration. This result revealed that PYL9, when driven by the pRD29A promoter, is useful for generating transgenic plants that are extremely resistant to drought when treated with ABA or ABAmimicking compounds (26,27). We chose the pRD29A::PYL9 transgenic lines for additional study (Fig.…”

C2-Domain Abscisic Acid-Related Proteins Mediate the Interaction of PYR/PYL/RCAR Abscisic Acid Receptors with the Plasma Membrane and Regulate Abscisic Acid Sensitivity in Arabidopsis

“…Structural and biochemical studies also reveal several divergences among PYR/PYLs, particularly with respect to oligomeric structure and the perception of chemical agonists (Dupeux et al, 2011b;Hao et al, 2011;Okamoto et al, 2013). Activation of dimeric receptors by the ABA agonist quinabactin, which also activates to some extent PYL5 and PYL7, is enough to elicit both seed and vegetative responses to ABA (Cao et al, 2013;Okamoto et al, 2013).…”

Abscisic acid sensor RCAR7/PYL13, specific regulator of protein phosphatase coreceptors

“…ABA binding stabilizes the RCAR-PP2C complex and releases PP2C downstream targets from the latent inhibition by the protein phosphatase (9,10); however, a few RCAR members are capable of regulating PP2Cs in the absence of ABA (11). ABA holo-receptors strongly discriminate against both nonphysiological ABA stereoisomers (8,12) and ABA biosynthetic precursors (13), but some receptor complexes tolerate binding of structurally unrelated ABA agonists (7,(14)(15)(16).…”