*Article* **The Role of ABA in Plant Immunity is Mediated through the PYR1 Receptor**

**Javier García-Andrade, Beatriz González, Miguel Gonzalez-Guzman , Pedro L. Rodriguez and Pablo Vera \***

Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-C.S.I.C, Ciudad Politécnica de la Innovación, Edificio 8E, 46000 Valencia, Spain; jagarsercs@gmail.com (J.G.-A.); beagong1@ibmcp.upv.es (B.G.); mguzman@uji.es (M.G.-G.); prodriguez@ibmcp.upv.es (P.L.R.) **\*** Correspondence: vera@ibmcp.upv.es; Tel.: +34-963877884; Fax: +34-963877859

Received: 16 July 2020; Accepted: 9 August 2020; Published: 14 August 2020

**Abstract:** ABA is involved in plant responses to a broad range of pathogens and exhibits complex antagonistic and synergistic relationships with salicylic acid (SA) and ethylene (ET) signaling pathways, respectively. However, the specific receptor of ABA that triggers the positive and negative responses of ABA during immune responses remains unknown. Through a reverse genetic analysis, we identified that PYR1, a member of the family of PYR/PYL/RCAR ABA receptors, is transcriptionally upregulated and specifically perceives ABA during biotic stress, initiating downstream signaling mediated by ABA-activated SnRK2 protein kinases. This exerts a damping effect on SA-mediated signaling, required for resistance to biotrophic pathogens, and simultaneously a positive control over the resistance to necrotrophic pathogens controlled by ET. We demonstrated that PYR1-mediated signaling exerted control on a priori established hormonal cross-talk between SA and ET, thereby redirecting defense outputs. Defects in ABA/PYR1 signaling activated SA biosynthesis and sensitized plants for immune priming by poising SA-responsive genes for enhanced expression. As a trade-off effect, *pyr1*-mediated activation of the SA pathway blunted ET perception, which is pivotal for the activation of resistance towards fungal necrotrophs. The specific perception of ABA by PYR1 represented a regulatory node, modulating different outcomes in disease resistance.

**Keywords:** ABA; ethylene; pathogens; plant immunity; PYR1; salicylic acid
