Evolutionary-based remodeling of ABA receptors reveals the structural basis of hormone perception and regulation

MpPYL1 enforce dimerization and lower ABA affinity. In planta, reporter assays and mutant analyses reveal complementary operating ranges: Monomeric, high-affinity receptors decode low ABA under mild stress, while dimeric, reduced-affinity receptors sustain signaling at high ABA during acute drought, expanding the system's overall dynamic range and robustness. These results resolve the apparent paradox of low-affinity dimers as an evolutionary innovation rather than a loss of sensitivity, link receptor architecture to ABA-mediated response, and provide actionable design principles for engineering ABA signaling to enhance crop drought resilience.