Abstract
We show that seed-specific overexpression of the sunflower (Helianthus annuus) HaHSFA9 heat stress transcription factor (HSF) in tobacco (Nicotiana tabacum) enhances the accumulation of heat shock proteins (HSPs). Among these proteins were HSP101 and a subset of the small HSPs, including proteins that accumulate only during embryogenesis in the absence of thermal stress. Levels of late embryogenesis abundant proteins or seed oligosaccharides, however, were not affected. In the transgenic seeds, a high basal thermotolerance persisted during the early hours of imbibition. Transgenic seeds also showed significantly improved resistance to controlled deterioration in a stable and transgene-dependent manner. Furthermore, overexpression of HaHSFA9 did not have detrimental effects on plant growth or development, including seed morphology and total seed yield. Our results agree with previous work tentatively associating HSP gene expression with phenotypes important for seed longevity. These findings might have implications for improving seed longevity in economically important crops.
Highlights
We show that seed-specific overexpression of the sunflower (Helianthus annuus) HaHSFA9 heat stress transcription factor (HSF) in tobacco (Nicotiana tabacum) enhances the accumulation of heat shock proteins (HSPs)
Among the genes with potential roles in seed longevity are those coding for small heat shock proteins since they contribute to different processes that have been associated with seed longevity (Wehmeyer and Vierling, 2000; Sun et al, 2002; Tsvetkova et al, 2002), such as thermotolerance, tolerance to embryo desiccation, membrane stabilization, and oxidative stress resistance
We have tested the effects of seed-specific overexpression of HaHSFA9 in transgenic tobacco (Nicotiana tabacum) under the control of the promoter and additional 5#- and 3#-flanking sequences from HaDS10G1 (DS10), which is an unusual late embryogenesis abundant (LEA) gene expressed in sunflower seeds from mid-maturation
Summary
We show that seed-specific overexpression of the sunflower (Helianthus annuus) HaHSFA9 heat stress transcription factor (HSF) in tobacco (Nicotiana tabacum) enhances the accumulation of heat shock proteins (HSPs). Germination efficiency and seed longevity involve the expression of multiple genes Attempts to identify such genes have involved the use of mutants (Ooms et al, 1993; Clerkx et al, 2004a; Sattler et al, 2004), or analyses of allelic variation in model plants (Clerkx et al, 2004b) and crops (Miura et al, 2002). We have tested the effects of seed-specific overexpression of HaHSFA9 in transgenic tobacco (Nicotiana tabacum) under the control of the promoter and additional 5#- and 3#-flanking sequences from HaDS10G1 (DS10), which is an unusual late embryogenesis abundant (LEA) gene (of group 1 [Wise 2003]) expressed in sunflower seeds from mid-maturation.
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