title: New ABA-hypersensitive Arabidopsis mutants are affected in loci mediating responses to water deficit and Dickeya dadantii infection.
abstract: On water deficit, abscisic acid (ABA) induces stomata closure to reduce water loss by transpiration. To identify Arabidopsis thaliana mutants which transpire less on drought, infrared thermal imaging of leaf temperature has been used to screen for suppressors of an ABA-deficient mutant (aba3-1) cold-leaf phenotype. Three novel mutants, called hot ABA-deficiency suppressor (has), have been identified with hot-leaf phenotypes in the absence of the aba3 mutation. The defective genes imparted no apparent modification to ABA production on water deficit, were inherited recessively and enhanced ABA responses indicating that the proteins encoded are negative regulators of ABA signalling. All three mutants showed ABA-hypersensitive stomata closure and inhibition of root elongation with little modification of growth and development in non-stressed conditions. The has2 mutant also exhibited increased germination inhibition by ABA, while ABA-inducible gene expression was not modified on dehydration, indicating the mutated gene affects early ABA-signalling responses that do not modify transcript levels. In contrast, weak ABA-hypersensitivity relative to mutant developmental phenotypes suggests that HAS3 regulates drought responses by both ABA-dependent and independent pathways. has1 mutant phenotypes were only apparent on stress or ABA treatments, and included reduced water loss on rapid dehydration. The HAS1 locus thus has the required characteristics for a targeted approach to improving resistance to water deficit. In contrast to has2, has1 exhibited only minor changes in susceptibility to Dickeya dadantii despite similar ABA-hypersensitivity, indicating that crosstalk between ABA responses to this pathogen and drought stress can occur through more than one point in the signalling pathway.
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, AgroParisTech, Versailles, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Plessis
authors.forename: Raphaël
authors.initials: R
authors.lastname: Cournol
authors.forename: Delphine
authors.initials: D
authors.lastname: Effroy
authors.forename: Viridiana
authors.initials: V
authors.lastname: Silva Pérez
authors.forename: Lucy
authors.initials: L
authors.lastname: Botran
authors.forename: Yvan
authors.initials: Y
authors.lastname: Kraepiel
authors.forename: Anne
authors.initials: A
authors.lastname: Frey
authors.forename: Bruno
authors.initials: B
authors.lastname: Sotta
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cornic
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Leung
authors.forename: Jérôme
authors.initials: J
authors.lastname: Giraudat
authors.forename: Annie
authors.initials: A
authors.lastname: Marion-Poll
authors.forename: Helen M
authors.initials: HM
authors.lastname: North
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D004755:Enterobacteriaceae / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D054884:Host-Pathogen Interactions; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013696:Temperature; D014867:Water / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D014867:Water; D000040:Abscisic Acid