title: The ectopic overexpression of a seed-specific transcription factor, HaHSFA9, confers tolerance to severe dehydration in vegetative organs.
abstract: Most plant seeds tolerate desiccation, but vegetative tissues are intolerant to drastic dehydration, except in the case of resurrection plants. Therefore, changes in the regulation of genes normally expressed in seeds are thought to be responsible for the evolutionary origin of desiccation tolerance in resurrection plants. Here, we show that constitutive overexpression of the seed-specific HSFA9 transcription factor from sunflower is sufficient to confer tolerance to severe dehydration, outside of the developing seed context, to vegetative tissues of transgenic tobacco. Whole 3-week-old seedlings could survive severe dehydration. This was quantified as a water loss to 1.96 +/- 0.05% of the initial water content, which corresponds to a water potential of approximately -40 MPa. Survival depended on the water potential, from 40% survival at approximately -20 MPa to 6.5% survival at approximately -40 MPa. Whole-seedling survival was limited by the dehydration sensitivity of the roots. Survival correlated with the ectopic expression of a genetic program involving seed-specific, small heat-shock proteins, but not late embryogenesis abundant proteins. The accumulation of sucrose or raffinose family oligosaccharides was not altered by HSFA9. The observed tolerance was achieved without a reduction of growth and development. Our results strongly support the previously suggested contribution of small heat-shock proteins to the desiccation tolerance of seeds. We provide a successful system for analyzing tolerance to severe dehydration in all vegetative organs of seedlings. We propose that HSFA9 is a potential genetic switch involved in the evolution of tolerance to vegetative desiccation.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, Consejo Superior de Investigaciones Científicas, Apartado 1052, 41080 Seville, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Prieto-Dapena
authors.forename: Raúl
authors.initials: R
authors.lastname: Castaño
authors.forename: Concepción
authors.initials: C
authors.lastname: Almoguera
authors.forename: Juan
authors.initials: J
authors.lastname: Jordano
mesh_terms: D003890:Desiccation; D018506:Gene Expression Regulation, Plant; D006368:Helianthus / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000235:genetics / Q000502:physiology*; D014026:Nicotiana / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014867:Water / Q000502:physiology
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors; D014867:Water