title: The Arabidopsis tetratricopeptide repeat-containing protein TTL1 is required for osmotic stress responses and abscisic acid sensitivity.
abstract: Mutations in the Arabidopsis (Arabidopsis thaliana) TETRATRICOPEPTIDE-REPEAT THIOREDOXIN-LIKE 1 (TTL1) cause reduced tolerance to NaCl and osmotic stress that is characterized by reduced root elongation, disorganization of the root meristem, and impaired osmotic responses during germination and seedling development. Expression analyses of genes involved in abscisic acid (ABA) biosynthesis and catabolism suggest that TTL1 is not involved in the regulation of ABA levels but is required for ABA-regulated responses. TTL1 regulates the transcript levels of several dehydration-responsive genes, such as the transcription factor DREB2A, and genes encoding dehydration response proteins, such as ERD1 (early response to dehydration 1), ERD3, and COR15a. The TTL1 gene encodes a novel plant protein with tetratricopeptide repeats and a region with homology to thioredoxin proteins. Based on homology searches, there are four TTL members in the Arabidopsis genome with similar intron-exon structure and conserved amino acid domains. Proteins containing tetratricopeptide repeat motifs act as scaffold-forming multiprotein complexes and are emerging as essential elements for plant hormonal responses (such as gibberellin responses and ethylene biosynthesis). In this report, we identify TTL1 as a positive regulator of ABA signaling during germination and seedling development under stress.
authors.affiliation: Departamento de Biología Molecular y Bioquímica Universidad de Málaga, 29010 Málaga, Spain.
authors.forename: Abel
authors.initials: A
authors.lastname: Rosado
authors.forename: Arnaldo L
authors.initials: AL
authors.lastname: Schapire
authors.forename: Ray A
authors.initials: RA
authors.lastname: Bressan
authors.forename: Antoine L
authors.initials: AL
authors.lastname: Harfouche
authors.forename: Paul M
authors.initials: PM
authors.lastname: Hasegawa
authors.forename: Victoriano
authors.initials: V
authors.lastname: Valpuesta
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Botella
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D010802:Phylogeny; D018517:Plant Roots / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C516469:TTL1 protein, Arabidopsis; D014867:Water; D000040:Abscisic Acid