title: Stress-responsive alpha-dioxygenase expression in tomato roots.
abstract: Alpha-dioxygenase (alpha-DOX) enzymes catalyse the oxygenation of fatty acids to yield a newly identified group of oxylipins that play a role in protecting tissues from oxidative damage and cell death. In tomato (Lycopersicon esculentum Mill.) alpha-DOX was identified as salt-regulated by differential display of mRNA, and is represented by a small gene family comprising at least three members: LEalpha-DOX1, -2, and -3 of which only LEalpha-DOX1 was salt-responsive. The enhancement of LEalpha-DOX1 expression in roots by salt, wounding and challenge with Pythium aphanidermatum (Edson) Fitzp. suggests that alpha-DOX-generated oxylipins may mediate the response of roots to these environmental stresses. In roots, LEalpha-DOX1 was abscisic acid (ABA)-responsive. However, in the ABA-deficient mutant flacca salt-responsive expression was equivalent to that in the wild type. Similarly, in roots exposed to fluridone (FLU) salt up-regulated expression; however, in this case salt-responsive LEalpha-DOX1 expression was greater than that in roots that were not exposed to FLU. A possible explanation for this is provided by the role of ABA in suppressing ethylene accumulation in osmotically stressed roots. The ethylene-generating agent ethephon and precursor 1-aminocyclopropane-1-carboxylic acid markedly elevated LEalpha-DOX1 expression, and this enhanced expression was suppressed by ABA. LEalpha-DOX1 expression in salt-stressed roots was not markedly affected by AVG indicating that ABA may be responsible for enhanced alpha-DOX expression in salt-treated roots.
authors.affiliation: Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6.
authors.forename: Ananchanok
authors.initials: A
authors.lastname: Tirajoh
authors.forename: Theingi S T
authors.initials: TS
authors.lastname: Aung
authors.forename: Ashley Byun
authors.initials: AB
authors.lastname: McKay
authors.forename: Aine L
authors.initials: AL
authors.lastname: Plant
mesh_terms: D000040:Abscisic Acid / Q000502:physiology; D000595:Amino Acid Sequence; D049308:Dioxygenases / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018551:Solanum lycopersicum / Q000201:enzymology*; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D018517:Plant Roots / Q000201:enzymology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D012965:Sodium Chloride
chemical_list: D005030:Ethylenes; D012965:Sodium Chloride; D000040:Abscisic Acid; C036216:ethylene; D049308:Dioxygenases