title: Protection of the photosynthetic apparatus from extreme dehydration and oxidative stress in seedlings of transgenic tobacco.
abstract: A genetic program that in sunflower seeds is activated by Heat Shock transcription Factor A9 (HaHSFA9) has been analyzed in transgenic tobacco seedlings. The ectopic overexpression of the HSFA9 program protected photosynthetic membranes, which resisted extreme dehydration and oxidative stress conditions. In contrast, heat acclimation of seedlings induced thermotolerance but not resistance to the harsh stress conditions employed. The HSFA9 program was found to include the expression of plastidial small Heat Shock Proteins that accumulate only at lower abundance in heat-stressed vegetative organs. Photosystem II (PSII) maximum quantum yield was higher for transgenic seedlings than for non-transgenic seedlings, after either stress treatment. Furthermore, protection of both PSII and Photosystem I (PSI) membrane protein complexes was observed in the transgenic seedlings, leading to their survival after the stress treatments. It was also shown that the plastidial D1 protein, a labile component of the PSII reaction center, and the PSI core protein PsaB were shielded from oxidative damage and degradation. We infer that natural expression of the HSFA9 program during embryogenesis may protect seed pro-plastids from developmental desiccation.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, Consejo Superior de Investigaciones Científicas, Seville, Spain.
authors.forename: Concepción
authors.initials: C
authors.lastname: Almoguera
authors.forename: Pilar
authors.initials: P
authors.lastname: Prieto-Dapena
authors.forename: José-María
authors.initials: JM
authors.lastname: Personat
authors.forename: Javier
authors.initials: J
authors.lastname: Tejedor-Cano
authors.forename: Marika
authors.initials: M
authors.lastname: Lindahl
authors.forename: Antonio
authors.initials: A
authors.lastname: Diaz-Espejo
authors.forename: Juan
authors.initials: J
authors.lastname: Jordano
mesh_terms: D000064:Acclimatization; D003681:Dehydration; D008565:Membrane Proteins / Q000378:metabolism; D018384:Oxidative Stress; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism; D059748:Proteolysis; D036226:Seedlings / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics* / Q000502:physiology*
chemical_list: D008565:Membrane Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins