PLANT PHYSIOLOGY , Vol 107, Issue 4 1439-1449, Copyright © 1995 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
The 5[prime] Flanking Regions of Vicilin and Napin Storage Protein Genes Are Down-Regulated by Desiccation in Transgenic Tobacco
L. Jiang, W. L. Downing, C. L. Baszczynski and A. R. Kermode
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (L.J., W.L.D., A.R.K.)
Drying of seeds, when imposed prematurely, elicits a switch in metabolism;
events unique to development, such as synthesis of storage protein, are
terminated, whereas syntheses associated with germination and growth are
initiated. To determine the role of desiccation in down-regulating the
expression of genes for storage proteins, the desiccation responsiveness of
the 5[prime] and 3[prime] regulatory regions of the genes encoding the pea
storage protein vicilin and the Brassica napus storage protein napin was
tested in transgenic tobacco seed. Chimeric genes were introduced into
tobacco; these genes consisted of the coding region of the reporter gene
for [beta]-glucuronidase (GUS) and 5[prime] and/or 3[prime] regions from
the vicilin or napin genes or, as controls, the same regions derived from
constitutively expressed genes, presumed to be desiccation insensitive. In
transgenic seed expressing the gene constructs containing the vicilin or
napin promoters, GUS activities declined during late seed development, and
more dramatically, after imbibition of mature dry seed or prematurely dried
seed. In contrast, GUS activities increased after seed rehydration when the
constitutive viral promoter replaced the storage-protein gene 5[prime]
region. Transient expression assays support the hypothesis that premature
drying down-regulates the expression of the storage-protein gene promoter.
Following desiccation, this region may become insensitive to positive
controlling factors; alternatively, changes to trans-acting factors may
occur.
