Arabidopsis PYR/PYL/RCAR Receptors Play a Major Role in Quantitative Regulation of Stomatal Aperture and Transcriptional Response to Abscisic Acid

[EN] Abscisic acid (ABA) is a key hormone for plant growth, development, and stress adaptation. Perception of ABA through four types of receptors has been reported. We show here that impairment of ABA perception through the PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR) branch reduces vegetative growth and seed production and leads to a severe open stomata and ABA-insensitive phenotype, even though other branches for ABA perception remain functional. An Arabidopsis thaliana sextuple mutant impaired in six PYR/PYL receptors, namely PYR1, PYL1, PYL2, PYL4, PYL5, and PYL8, was able to germinate and grow even on 100 mu M ABA. Whole-rosette stomatal conductance (Gst) measurements revealed that leaf transpiration in the sextuple pyr/pyl mutant was higher than in the ABA-deficient aba3-1 or ABA-insensitive snrk2.6 mutants. The gradually increasing Gst values of plants lacking three, four, five, and six PYR/PYLs indicate quantitative regulation of stomatal aperture by this family of receptors. The sextuple mutant lacked ABA-mediated activation of SnRK2s, and ABA-responsive gene expression was dramatically impaired as was reported in snrk2.2/2.3/2.6. In summary, these results show that ABA perception by PYR/PYLs plays a major role in regulation of seed germination and establishment, basal ABA signaling required for vegetative and reproductive growth, stomatal aperture, and transcriptional response to the hormone. We thank Joseph Ecker and the Salk Institute Genomic Analysis Laboratory for providing the sequence-indexed Arabidopsis T-DNA insertion mutants, the Arabidopsis Biological Resource Center/Nottingham Arabidopsis Stock Centre for distributing these seeds, and Sean Cutler for the pyr1-1, 114 and 1124 mutants. This study was supported by the Ministerio de Ciencia e Innovacion, Fondo Europeo de Desarrollo Regional, and Consejo Superior de Investigaciones Cientificas (grant BIO2011-23446 to P. L. R; fellowship to R. A.; Juan de la Cierva contract to M. G.-G.), by the Estonian Ministry of Science and Education (ETF7763 and ETF9208, SF0180071s07), by the European Regional Fund (Center of Excellence in Environmental Adaptation), and by a Marie Curie Incoming International Fellowship to G. W. B. González Guzmán, M.; Pizzio Bianchi, GA.; Antoni-Alandes, R.; Vera Sirera, FJ.; Merilo, E.; Bassel, G.; Fernandez, M... (2012). Arabidopsis PYR/PYL/RCAR Receptors Play a Major Role in Quantitative Regulation of Stomatal Aperture a