Characterization of a negatively light-regulated mRNA from Lemna gibba

Abstract

We have isolated a cDNA clone, called pLg106, which corresponds to a negatively light-regulated mRNA in the aquatic monocot Lemna gibba. Lg106 mRNA is more abundant in dark-treated plants than in plants grown under continuous white light. The levels of Lg106 mRNA reached a maximum 12-24 hours after plants had been placed in the dark. In vitro-labelled transcripts from nuclei isolated from white light-grown and darktreated Lemna hybridized equally to Lg106 DNA, indicating that transcription of the Lg106 gene was similar in both white light and darkness. Therefore, the higher level of Lg106 mRNA in the dark was not attributable to a change in transcription. We suggest that the stability of Lg106 mRNA is affected by changes in illumination. The steady-state level of Lg106 did not appear to be under phytochrome regulation, as the abundance of Lg106 mRNA from plants grown in intermittent red light or intermittent red followed immediately by far-red light was not significantly different from that of dark-treated plants. The size of the mRNA was estimated to be 650-700 nt. Genomic Southern blots indicated the presence of a single gene for Lg106. The Lg106 cDNA was sequenced and examined for similarities to nucleotide sequences in GenBank.

Dark-induced and organ-specific expression of two asparagine synthetase genes in Pisum sativum.

“…The dark-induced accumulation of the ASI mRNA classifies the AS 1 gene with other genes that are negatively regulated by light such as phytochrome (Otto et al, 1984;Lissemore and Quail, 1988;Kay et al, 1989), protochlorophyllide reductase (Mosinger et al, 1985) and an unidentified mRNA found in Lemna (Okubara et al, 1988). As shown for phytochrome (Lissemore and Quail, 1988;Kay et al, 1989) and protochlorophyllide reductase genes (Mosinger et al, 1985), the repression of ASI mRNA accumulation in the light is a phytochrome-mediated response.…”

“…As shown for phytochrome (Lissemore and Quail, 1988;Kay et al, 1989) and protochlorophyllide reductase genes (Mosinger et al, 1985), the repression of ASI mRNA accumulation in the light is a phytochrome-mediated response. However, it remains to be determined whether the dark-induced (or light-repressed) expression of ASI reflects a transcriptional response as has been shown for phytochrome (Lissemore and Quail, 1988;Kay et al, 1989) and protochlorophyllide reductase (Mosinger et al, 1985) or whether it represents a post-transcriptional response as has been shown for another dark-induced gene of unknown function (Okubara et al, 1988). In direct contrast to the dark-induced accumulation of AS1 mRNA in leaves, the mRNA for the chloroplast form of glutamine synthetase (GS2) accumulates in the light in a phytochrome-mediated response (Tingey et al, 1988).…”

Photoregulation of β-Tubulin mRNA Abundance in Etiolated Oat and Barley Seedlings

“…Downregulation of j3-tubulin mRNA abundance has also been observed after transfer of etiolated soybean seedlings to white light (1). The mRNA levels of at least 11 genes encoding unknown proteins (8,20) exposure of dark grown plants to white light. The mRNA abundance of at least one of these genes is unaffected by red light, indicating that this gene is not under phytochrome control (20).…”

“…The mRNA levels of at least 11 genes encoding unknown proteins (8,20) exposure of dark grown plants to white light. The mRNA abundance of at least one of these genes is unaffected by red light, indicating that this gene is not under phytochrome control (20). The down-regulation of the phytochrome, asparagine syntetase, and protochlorophyllide reductase mRNAs is phytochrome-mediated (4,5,19,29).…”