title: Phytochrome B increases drought tolerance by enhancing ABA sensitivity in Arabidopsis thaliana.
abstract: Phytochrome B (phyB) can adjust morphological and physiological responses according to changes in the red:far-red (R:FR) ratio. phyB-driven acclimation of plants to open environments (high R:FR ratio) increases carbon gain at the expense of increased water loss. This behaviour alleviates stressful conditions generated by an excess of light, but increases the chances of desiccation. Here we evaluated how phyB modulates this drought-tolerance response by comparing wild-type Arabidopsis thaliana adult plants to the null phyB in response to water shortage. phyB wilted before the wild type, and this was due to phyB maintaining open stomata under a reduction in soil water availability. Although phyB presented enhanced ABA levels under well-watered conditions, this mutant was less sensitive than the wild type in diminishing stomatal conductance in response to exogenous ABA application. Reduced sensitivity to ABA in phyB correlated with a lower expression of ABCG22, which encodes a putative ABA influx transporter, and PYL5, which encodes a soluble ABA receptor. Furthermore, the expression of RAB18 and RD29A, both typical ABA-induced genes, was lower in phyB than the wild type after ABA treatment. We propose that phyB contributes to the acclimation of plants to open environments by enhancing ABA sensitivity when soil water becomes limiting.
authors.affiliation: IBAM (Instituto de Biología Agrícola de Mendoza), CONICET-Universidad Nacional de Cuyo, Facultad de Ciencias Agrarias, Alte. Brown 500 (5505), Chacras de Coria, Luján de Cuyo, Mendoza, Argentina. cgonzalez@fca.uncu.edu.ar
authors.forename: Carina Verónica
authors.initials: CV
authors.lastname: González
authors.forename: Silvia Elizabeth
authors.initials: SE
authors.lastname: Ibarra
authors.forename: Patricia Noemí
authors.initials: PN
authors.lastname: Piccoli
authors.forename: Javier Francisco
authors.initials: JF
authors.lastname: Botto
authors.forename: Hernán Esteban
authors.initials: HE
authors.lastname: Boccalandro
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D051939:Phytochrome B / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D015398:Signal Transduction; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C497952:PHYB protein, Arabidopsis; D014867:Water; D051939:Phytochrome B; D000040:Abscisic Acid