Loss of function of the HSFA9 seed longevity program

Authors

  • JAVIER TEJEDOR-CANO,

    1. Departamento de Biotecnología Vegetal, Instituto de Recursos Naturales y Agrobiología de Sevilla, C.S.I.C. Apartado 1052. Sevilla, ES-41080, Spain and
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  • PILAR PRIETO-DAPENA,

    1. Departamento de Biotecnología Vegetal, Instituto de Recursos Naturales y Agrobiología de Sevilla, C.S.I.C. Apartado 1052. Sevilla, ES-41080, Spain and
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  • CONCEPCIÓN ALMOGUERA,

    1. Departamento de Biotecnología Vegetal, Instituto de Recursos Naturales y Agrobiología de Sevilla, C.S.I.C. Apartado 1052. Sevilla, ES-41080, Spain and
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  • RAÚL CARRANCO,

    1. Departamento de Biotecnología Vegetal, Instituto de Recursos Naturales y Agrobiología de Sevilla, C.S.I.C. Apartado 1052. Sevilla, ES-41080, Spain and
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  • KEIICHIRO HIRATSU,

    1. Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology (AIST), Central 4, Tsukuba 305-8562, Japan
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    • Present address: National Defense Academy of Japan, Yokosuka, Kanagawa 239-8686, Japan.

  • MASARU OHME-TAKAGI,

    1. Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology (AIST), Central 4, Tsukuba 305-8562, Japan
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  • JUAN JORDANO

    Corresponding author
    1. Departamento de Biotecnología Vegetal, Instituto de Recursos Naturales y Agrobiología de Sevilla, C.S.I.C. Apartado 1052. Sevilla, ES-41080, Spain and
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J. Jordano. Fax: + 34 954 624002; e-mail: fraga@cica.es

ABSTRACT

Gain of function approaches that have been published by our laboratory determined that HSFA9 (Heat Shock Factor A9) activates a genetic program contributing to seed longevity and to desiccation tolerance in plant embryos. We now evaluate the role(s) of HSFA9 by loss of function using different modified forms of HaHSFA9 (sunflower HSFA9), which were specifically overexpressed in seeds of transgenic tobacco. We used two inactive forms (M1, M2) with deletion or mutation of the transcription activation domain of HaHSFA9, and a third form (M3) with HaHSFA9 converted to a potent active repressor by fusion of the SRDX motif. The three forms showed similar protein accumulation in transgenic seeds; however, only HaHSFA9-SRDX showed a highly significant reduction of seed longevity, as determined by controlled deterioration tests, a rapid seed ageing procedure. HaHSFA9-SRDX impaired the genetic program controlled by the tobacco HSFA9, with a drastic reduction in the accumulation of seed heat shock proteins (HSPs) including seed-specific small HSP (sHSP) belonging to cytosolic (CI, CII) classes. Despite such effects, the HaHSFA9-SRDX seeds could survive developmental desiccation during embryogenesis and their subsequent germination was not reduced. We infer that the HSFA9 genetic program contributes only partially to seed-desiccation tolerance and longevity.

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