Abscisic acid (ABA) is a critical plant hormone, controlling developmental processes and immune responses. Long-term regulation of ABA signaling involves changes in gene expression that reduce ABA synthesis and enhance ABA metabolism. Castillo et al. found that various members of the ABA receptor PYR/PYL/RCAR family were modified posttranslationally by tyrosine nitration or S-nitrosylation at cysteine residues, two covalent modifications that can result from increased nitric oxide (NO). These NO-mediated modifications and polyubiquitylation, which target proteins for degradation, occurred in a complex, potentially interconnected, and receptor-specific pattern in plants overexpressing individual receptors. Tyrosine nitration, but not S-nitrosylation, inhibited ABA-induced activity in vitro, suggesting that tyrosine nitration may be a mechanism to rapidly tune the cellular responsiveness to ABA.