title: Tomato (Solanum lycopersicum L.) SlIPT3 and SlIPT4 isopentenyltransferases mediate salt stress response in tomato.
abstract: BACKGROUND
  Cytokinins (CKs) are involved in response to various environmental cues, including salinity. It has been previously reported that enhancing CK contents improved salt stress tolerance in tomato. However, the underlying mechanisms of CK metabolism and signaling under salt stress conditions remain to be deciphered.
  
  
  RESULTS
  Two tomato isopentenyltransferases, SlIPT3 and SlIPT4, were characterized in tomato and Arabidopsis. Both proteins displayed isopentenyltransferase (IPT) activity in vitro, while their encoding genes exhibited different spatio-temporal expression patterns during tomato plant development. SlIPT3 and SlIPT4 were affected by the endogenous CK status, tightly connected with CKs feedback regulation, as revealed by hormonal treatements. In response to salt stress, SlIPT3 and SlIPT4 were strongly repressed in tomato roots, and differently affected in young and old leaves. SlIPT3 overexpression in tomato resulted in high accumulation of different CK metabolites, following modifications of CK biosynthesis-, signaling- and degradation-gene expression. In addition, 35S::SlIPT3 tomato plants displayed improved tolerance to salinity consecutive to photosynthetic pigments and K(+)/Na(+) ratio retention. Involvement of SlIPT3 and SlIPT4 in salt stress response was also observed in Arabidopsis ipt3 knock-out complemented plants, through maintenance of CK homeostasis.
  
  
  CONCLUSIONS
  SlIPT3 and SlIPT4 are functional IPTs encoded by differently expressed genes, distinctively taking part in the salinity response. The substantial participation of SlIPT3 in CK metabolism during salt stress has been determined in 35S::SlIPT3 tomato transformants, where enhancement of CKs accumulation significantly improved plant tolerance to salinity, underlining the importance of this phytohormone in stress response.
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. zizkovae@ueb.cas.cz.
authors.forename: Eva
authors.initials: E
authors.lastname: Žižková
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. dobrev@ueb.cas.cz.
authors.forename: Petre I
authors.initials: PI
authors.lastname: Dobrev
authors.affiliation: Département Sciences du vivant, Centre wallon de Recherches Agronomiques, Gembloux, B-5030, Belgium. muhovski@cra.wallonie.be.
authors.forename: Yordan
authors.initials: Y
authors.lastname: Muhovski
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. hosekpe2@fbmi.cvut.cz.|Department of Biomedical Informatics, Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, 272 01, Czech Republic. hosekpe2@fbmi.cvut.cz.
authors.forename: Petr
authors.initials: P
authors.lastname: Hošek
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. hoyerova@ueb.cas.cz.
authors.forename: Klára
authors.initials: K
authors.lastname: Hoyerová
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. haisel@ueb.cas.cz.
authors.forename: Daniel
authors.initials: D
authors.lastname: Haisel
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. prochazkovad@ueb.cas.cz.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Procházková
authors.affiliation: Groupe de Recherche en Physiologie Végétale (GRPV), Earth and Life Institute - Agronomy (ELI-A), Université catholique de Louvain (UCL), Louvain-la-Neuve, 1348, Belgium. Stanley.Lutts@uclouvain.be.
authors.forename: Stanley
authors.initials: S
authors.lastname: Lutts
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague, 165 02, Czech Republic. motyka@ueb.cas.cz.
authors.forename: Václav
authors.initials: V
authors.lastname: Motyka
authors.affiliation: Groupe de Recherche en Physiologie Végétale (GRPV), Earth and Life Institute - Agronomy (ELI-A), Université catholique de Louvain (UCL), Louvain-la-Neuve, 1348, Belgium. imene.hichri@sophia.inra.fr.|Institut National de la Recherche Agronomique, Institut Sophia Agrobiotech (ISA), UMR INRA 1355, CNRS 7254, Université de Nice-Sophia Antipolis, 400 route des Chappes, BP167, F-06903, Sophia-Antipolis Cedex, France. imene.hichri@sophia.inra.fr.
authors.forename: Imène
authors.initials: I
authors.lastname: Hichri
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D003583:Cytokinins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000196:embryology / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D055049:Salt Tolerance
chemical_list: D003583:Cytokinins; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase