An inverse control by phytochrome of the expression of two nuclear genes in barley (Hordeum vulgave L.)

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Abstract
During the light-dependent transformation of etioplasts to chloroplasts a rapid decrease of the NADPH-protochlorophyllide oxidoreductase is induced. At the same time the mRNA activity coding for this enzyme protein also declines rapidly under the influence of phytochrome (Pfr [far red absorbing form]). The apoprotein of the light-harvesting chlorophyll a/b protein and its mRNA activity are inversely affected by the same photoreceptor. Cloned c[complementary]DNA sequences which are complementary to these mRNA were used to assess the effect of phytochrome (Pfr) on the concentration of the 2 transcripts. The phytochrome-induced changes of the 2 translatable mRNA are paralleled by corresponding changes in the steady-state concentration of the mRNA sequences. This inverse relationship between the light-dependent regulation of the NADPH-protochlorophyllide oxidoreductase and the light-harvesting chlorophyll a/b protein suggests that a single reversible triggering event can increase the transcription of certain genes and decrease the transcription of others.