Phytochrome control of in vitro transcription of specific genes in isolated nuclei from barley (Hordeum vulgare)

Abstract

The transcriptional rates of four different genes in shoots of barley grown under different light regimes were quantified by monitoring nuclear RNA transcripts, using gene-specific hybridization probes. Isolated nuclei were pulse-labelled with [.alpha.-32P]UTP and the relative rates of light-harvesting chlorophyll a/b protein (LHCP) mRNA. NADPH:protochlorophyllide oxidoreductase [messenger] mRNA, B1 hordein mRNA, and 26-S [ribosomal] rRNA synthesis were measured. Irradiation of dark-grown plants with a red light pulse increased the rate of LHCP mRNA synthesis 10-fold within 3 h, and it increased the rate of rRNA synthesis more than 2-fold within 9 h. The relative rate of synthesis of the oxidoreductase mRNA decreased following a red light pulse, reaching a minimum after 3-6 h. As a direct proof of phytochrome involvement in the light-induced stimulation of LHCP and the repression of the oxidoreductase transcripts for both responses, red/far-red reversibility could be demonstrated. Apparently, phytochrome is able both to increase the transcription of certain nuclear genes and to decrease the transcription of others.