title: The redox-sensitive chloroplast trehalose-6-phosphate phosphatase AtTPPD regulates salt stress tolerance.
abstract: OBJECTIVE
  High salinity stress impairs plant growth and development. Trehalose metabolism has been implicated in sugar signaling, and enhanced trehalose metabolism can positively regulate abiotic stress tolerance. However, the molecular mechanism(s) of the stress-related trehalose pathway and the role of individual trehalose biosynthetic enzymes for stress tolerance remain unclear.
  
  
  RESULTS
  Trehalose-6-phosphate phosphatase (TPP) catalyzes the final step of trehalose metabolism. Investigating the subcellular localization of the Arabidopsis thaliana TPP family members, we identified AtTPPD as a chloroplast-localized enzyme. Plants deficient in AtTPPD were hypersensitive, whereas plants overexpressing AtTPPD were more tolerant to high salinity stress. Elevated stress tolerance of AtTPPD overexpressors correlated with high starch levels and increased accumulation of soluble sugars, suggesting a role for AtTPPD in regulating sugar metabolism under salinity conditions. Biochemical analyses indicate that AtTPPD is a target of post-translational redox regulation and can be reversibly inactivated by oxidizing conditions. Two cysteine residues were identified as the redox-sensitive sites. Structural and mutation analyses suggest that the formation of an intramolecular disulfide bridge regulates AtTPPD activity.
  
  
  METHODS
  The activity of different AtTPP isoforms, located in the cytosol, nucleus, and chloroplasts, can be redox regulated, suggesting that the trehalose metabolism might relay the redox status of different cellular compartments to regulate diverse biological processes such as stress responses.
  
  
  CONCLUSIONS
  The evolutionary conservation of the two redox regulatory cysteine residues of TPPs in spermatophytes indicates that redox regulation of TPPs might be a common mechanism enabling plants to rapidly adjust trehalose metabolism to the prevailing environmental and developmental conditions.
authors.affiliation: GMI-Gregor Mendel Institute of Molecular Plant Biology , Austrian Academy of Sciences, Vienna, Austria .
authors.forename: Julia
authors.initials: J
authors.lastname: Krasensky
authors.forename: Caroline
authors.initials: C
authors.lastname: Broyart
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Rabanal
authors.forename: Claudia
authors.initials: C
authors.lastname: Jonak
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological
chemical_list: D012965:Sodium Chloride; C023178:trehalose-phosphatase; D010744:Phosphoric Monoester Hydrolases