title: Adaptation to high salinity in poplar involves changes in xylem anatomy and auxin physiology.
abstract: To investigate the physiological basis of salt adaptation in poplar, we compared the effect of salt stress on wood anatomy and auxin physiology of the salt-resistant Populus euphratica and salt-sensitive Populus x canescens. Both poplar species showed decreases in vessel lumina associated with increases in wall strength in response to salt, however, in P. euphratica at three-fold higher salt concentrations than in P. x canescens. The predicted hydraulic conductivity of the wood formed under salt stress decreased in P. x canescens, while in P. euphratica, no significant effects of salt on conductivity and transpiration were observed. The concentration of free indole-3-acetic acid (IAA) decreased under salt stress in the xylem of both poplar species, but to a larger extent in P. x canescens than in P. euphratica. Only salt-treated P. euphratica exhibited an increase in IAA-conjugates in the xylem. Genes homologous to the auxin-amidohydrolase ILL3 were isolated from the xylems of P. euphratica and P. x canescens. For functional analysis, the auxin-amidohydrolase from P. x canescens was overexpressed in Arabidopsis. Transgenic Arabidopsis plants were more resistant to salt stress than the wild-type plants. Increased sensitivity of the transgenic Arabidopsis to IAA-Leu showed that the encoded hydrolase used IAA-Leu as a substrate. These results suggest that poplar can use IAA-amidoconjugates in the stem as a source of auxin to balance the effects of salt stress on auxin physiology.
authors.affiliation: Institut für Forstbotanik, Georg-August-Universität Göttingen, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Junghans
authors.forename: A
authors.initials: A
authors.lastname: Polle
authors.forename: P
authors.initials: P
authors.lastname: Düchting
authors.forename: E
authors.initials: E
authors.lastname: Weiler
authors.forename: B
authors.initials: B
authors.lastname: Kuhlman
authors.forename: F
authors.initials: F
authors.lastname: Gruber
authors.forename: T
authors.initials: T
authors.lastname: Teichmann
mesh_terms: D000222:Adaptation, Physiological; D000581:Amidohydrolases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D017343:Genes, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology; D032107:Populus / Q000033:anatomy & histology* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D012965:Sodium Chloride / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D012965:Sodium Chloride; C030737:indoleacetic acid; D000581:Amidohydrolases