| Summary: | 博士 === 國立清華大學 === 生物資訊與結構生物研究所 === 101 === A novel dehydrin gene (VrDhn1) was isolated from an embryo cDNA library of Vigna radiata (L.) Wilczek (mungbean) variety VC1973A. The intronless VrDhn1 gene encodes a protein belonging to the Y2K-type dehydrin family. VrDhn1 protein accumulated in embryos and cotyledons during seed maturation and disappeared 2 days after seed imbibition (DAI). The expression of VrDhn1 mRNA and accumulation of VrDhn1 protein were at high levels in mature seeds, but neither mRNA nor protein was detected in mungbean vegetative tissues under normal growth conditions. VrDhn1 mRNA level was extremely high in mature seeds and decreased to ~30% at 1 DAI, and was not detectable at ~7 DAI. Tissue dehydration, salinity and exogenous abscisic acid (ABA) markedly induced VrDhn1 transcripts in plants as measured by quantitative real-time reverse transcription-PCR (qRT-PCR). VrDhn1 protein was not detected using immunoblots in seedlings under stress treatments. VrDhn1:GFP fusion protein is degraded in transgenic Arabidopsis under normal condition, but is more stable under dehydration. In mature seeds or 1 DAI seedlings, VrDhn1 proteins were immunolocalized in the nucleus and cytoplasm. VrDhn1 exhibited low affinity of non-specific interaction with DNA using electrophoretic mobility shift assays (EMSA), and the exogenous addition of Zn2+ or Ni2+ stimulated interaction. Phosphorylation occurs on threonine and tyrosine residues of VrDhn1 in mungbean seeds. The His-tagged VrDhn1 (30.17 kDa) protein showed a molecular mass of 63.1 kDa on gel filtration, suggesting a dimer form. This is the first report showing that a Y2K-type VrDhn1 enters the nucleus and interacts with DNA during seed maturation.
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