Prieto-Dapena Pilar, Castaño Raúl, Almoguera Concepción, Jordano Juan
Instituto de Recursos Naturales y Agrobiología de Sevilla, Consejo Superior de Investigaciones Científicas, Apartado 1052, 41080 Seville, Spain.
Plant J. 2008 Jun;54(6):1004-14. doi: 10.1111/j.1365-313X.2008.03465.x. Epub 2008 Mar 1.
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.
大多数植物种子能够耐受干燥，但营养组织不耐受剧烈脱水，复苏植物除外。因此，种子中正常表达的基因调控变化被认为是复苏植物耐旱性进化起源的原因。在此，我们表明，来自向日葵的种子特异性HSFA9转录因子的组成型过表达足以使转基因烟草的营养组织在发育种子之外的环境中耐受严重脱水。3周龄的完整幼苗能够在严重脱水条件下存活。这被量化为水分损失至初始含水量的1.96±0.05%，这对应于约-40 MPa的水势。存活率取决于水势，在约-20 MPa时存活率为40%，在约-40 MPa时存活率为6.5%。整株幼苗的存活受根部脱水敏感性的限制。存活与涉及种子特异性小热激蛋白而非晚期胚胎发生丰富蛋白的遗传程序的异位表达相关。HSFA9并未改变蔗糖或棉子糖家族寡糖的积累。在不影响生长和发育的情况下实现了观察到的耐受性。我们的结果有力地支持了先前提出的小热激蛋白对种子耐旱性的贡献。我们提供了一个成功的系统，用于分析幼苗所有营养器官对严重脱水的耐受性。我们提出，HSFA9是参与营养组织耐旱性进化的潜在遗传开关。
