title: Compound stress response in stomatal closure: a mathematical model of ABA and ethylene interaction in guard cells.
abstract: BACKGROUND
  Stomata are tiny pores in plant leaves that regulate gas and water exchange between the plant and its environment. Abscisic acid and ethylene are two well-known elicitors of stomatal closure when acting independently. However, when stomata are presented with a combination of both signals, they fail to close.
  
  
  RESULTS
  Toshed light on this unexplained behaviour, we have collected time course measurements of stomatal aperture and hydrogen peroxide production in Arabidopsis thaliana guard cells treated with abscisic acid, ethylene, and a combination of both. Our experiments show that stomatal closure is linked to sustained high levels of hydrogen peroxide in guard cells. When treated with a combined dose of abscisic acid and ethylene, guard cells exhibit increased antioxidant activity that reduces hydrogen peroxide levels and precludes closure. We construct a simplified model of stomatal closure derived from known biochemical pathways that captures the experimentally observed behaviour.
  
  
  CONCLUSIONS
  Our experiments and modelling results suggest a distinct role for two antioxidant mechanisms during stomatal closure: a slower, delayed response activated by a single stimulus (abscisic acid 'or' ethylene) and another more rapid 'and' mechanism that is only activated when both stimuli are present. Our model indicates that the presence of this rapid 'and' mechanism in the antioxidant response is key to explain the lack of closure under a combined stimulus.
authors.affiliation: Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK.
authors.forename: Mariano
authors.initials: M
authors.lastname: Beguerisse-Dıaz
authors.forename: Mercedes C
authors.initials: MC
authors.lastname: Hernández-Gómez
authors.forename: Alessandro M
authors.initials: AM
authors.lastname: Lizzul
authors.forename: Mauricio
authors.initials: M
authors.lastname: Barahona
authors.forename: Radhika
authors.initials: R
authors.lastname: Desikan
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000033:anatomy & histology / Q000166:cytology* / Q000378:metabolism / Q000502:physiology*; D005030:Ethylenes / Q000378:metabolism*; D008954:Models, Biological; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D013997:Time Factors
chemical_list: D005030:Ethylenes; D017382:Reactive Oxygen Species; D000040:Abscisic Acid; C036216:ethylene