title: Dehydrins are highly expressed in overwintering buds and enhance drought and freezing tolerance in Gentiana triflora.
abstract: Gentians, herbaceous perennials, produce overwintering buds (OWBs) to survive the cold season. Although gentians are known to have strong stress tolerances against drought, cold and freezing, the molecular mechanisms of tolerance are unclear. We explored genes more highly expressed in OWBs than in other tissues and identified two gentian orthologs of dehydrins, denoted GtDHN1 and GtDHN2. These GtDHNs possess several ABA or dehydration responsive elements. Furthermore, GtDHN1 and GtDHN2 transcripts in OWBs accumulated during the winter but decreased prior to spring, suggesting that GtDHNs may be induced by dehydration stress during cold periods and may act as a stress protectant mediated by ABA. Likewise, cultured gentian plantlets accumulated GtDHN transcripts in response to ABA as well as cold and drought stresses. Moreover, transgenic gentian plantlets overexpressing GtDHN1 or GtDHN2 showed improved cold and drought stress tolerance. Metabolome analysis revealed that major antioxidants such as glutathione and ascorbate were accumulated in all transgenic plantlets. Overexpression of GtDHNs also affected the activities of the antioxidant enzymes, ascorbate peroxidase and glutathione peroxidase. Based on the results of this study, GtDHNs are induced by ABA and dehydration stress and have an ability to alleviate dehydration stress, probably via activating antioxidant mechanisms. Accumulation of GtDHNs may be part of the strategy for winter survival of gentian OWBs.
authors.affiliation: Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate 024-0003, Japan. Electronic address: timamura@ibrc.or.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Imamura
authors.forename: Atsumi
authors.initials: A
authors.lastname: Higuchi
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D003681:Dehydration; D055864:Droughts; D005615:Freezing; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D030012:Gentiana / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D012492:Salts; D012621:Seasons; D036226:Seedlings / Q000235:genetics / Q000502:physiology; D016415:Sequence Alignment; D013312:Stress, Physiological
chemical_list: D010937:Plant Growth Regulators; D010940:Plant Proteins; D012492:Salts; C070556:dehydrin proteins, plant; D000040:Abscisic Acid
keywords: Ascorbate; Dehydration stress tolerance; Dehydrin; Gentiana triflora; Glutathione; Over-wintering bud