PLANT PHYSIOLOGY , Vol 105, Issue 3 949-954, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
NPR Genes, Which Are Negatively Regulated by Phytochrome Action in Lemna gibba L. G-3, Can Also Be Positively Regulated by Abscisic Acid
S. A. Williams, S. C. Weatherwax, E. A. Bray and E. M. Tobin
Department of Biology, University of California, Los Angeles, California 90024-1606
We have found that NPR1 and NPR2, two genes from Lemna gibba L. G-3 that
can be negatively regulated by phytochrome action, can also be positively
regulated by the plant hormone abscisic acid (ABA). Both genes were
responsive to low concentrations of exogenous ABA; an increase in NPR1 RNA
could be detected in response to concentrations as low as 10 nM. We have
also tested phytochrome responsiveness of 5[prime] promoter-deletion
constructs of one of these genes, NPR1, in transient assays utilizing
particle bombardment. This analysis demonstrated that DNA sequences
important for phytochrome regulation are present downstream of -198 from
the transcription start site. A response to ABA treatment could also be
observed in the transient assay system.When intact plants were placed in
darkness, there was an increase in ABA levels as well as increased levels
of NPR1 and NPR2 RNA.