Immune signaling and drought tolerance mediated by NDR1-AHA5 regulation of H⁺-ATPase, guard cells, and homeostasis.

key messageNDR1 and AHA5 coordinate drought stress and immune responses via stomatal regulation, uncovering a molecular link between abiotic and biotic stress adaptation in Arabidopsis. Plant stress responses have overlapping molecular and physiological signatures. Not surprisingly, many of these are also shared with numerous other processes, including growth and development, as well as abiotic and biotic signaling. NON-RACE-SPECIFIC DISEASE RESISTANCE1 (NDR1) is a key component of plant immune signaling, required for defense against the bacterial pathogen Pseudomonas syringae. In this study, we have identified that NDR1 contributes to stomatal-based processes following exposure to biotic (flg22 (flagellin peptide) and elf26 (EF-Tu-related elicitor)) and abiotic (ABA, drought, etc.) elicitors. Interestingly, we found that NDR1 is part of a signaling cascade that confers tolerance to water loss-a required component of drought stress responses in plants, a role that couples stress signaling in an abscisic acid-dependent manner. As a definition of its broader connectivity to this response, we identified that NDR1 physically associates with the PM-localized H