title: Identification of two-component system elements downstream of AHK5 in the stomatal closure response of Arabidopsis thaliana.
abstract: To optimize water use efficiency, plants regulate stomatal closure through a complex signaling process. Hydrogen peroxide (H₂O₂) is produced in response to several environmental stimuli, and has been identified as a key second messenger involved in the regulation of stomatal aperture. The Arabidopsis histidine kinase 5 (AHK5) has been shown to regulate stomatal closure in response to H₂O₂ and other stimuli that depend on H₂O₂. AHK5 is a member of the two-component system (TCS) in Arabidopsis. The plant TCS comprises three different protein types: the hybrid histidine kinases (HKs), the phosphotransfer proteins (HPs) and the response regulators (RRs). Here we determined TCS elements involved in H₂O₂- and ethylene-dependent stomatal closure downstream of AHK5. By yeast and in planta interaction assays and functional studies, AHP1, 2 and 5 as well as the response regulators ARR4 and ARR7 were identified acting downstream of AHK5 in the ethylene and H₂O₂ response pathways of guard cells. Furthermore, we demonstrate that aspartate phosphorylation of ARR4 is only required for the H₂O₂- but not for the ethylene-induced stomatal closure response. Our data suggest the presence of a complex TCS signaling network comprising of at least AHK5, several AHPs and response regulators, which modulate stomatal closure in response to H₂O₂ and ethylene.
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Tübingen, Germany.
authors.forename: Virtudes
authors.initials: V
authors.lastname: Mira-Rodado
authors.forename: Manikandan
authors.initials: M
authors.lastname: Veerabagu
authors.forename: Janika
authors.initials: J
authors.lastname: Witthöft
authors.forename: Julia
authors.initials: J
authors.lastname: Teply
authors.forename: Klaus
authors.initials: K
authors.lastname: Harter
authors.forename: Radhika
authors.initials: R
authors.lastname: Desikan
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism; D000071677:Histidine Kinase; D006861:Hydrogen Peroxide / Q000378:metabolism; D010766:Phosphorylation; D054046:Plant Stomata / Q000378:metabolism* / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D005030:Ethylenes; C036216:ethylene; D006861:Hydrogen Peroxide; D011494:Protein Kinases; D000071677:Histidine Kinase