Sugar effect on the malate synthase and isocitrate lyase gene expression at the level of mRNA stability
1. Ismail* and S.M. Smith
Institute of Cell and Molecular Biology, University of Edinburgh, the King's Buildings, Mayfield Road, Edinburgh, EH9 3JH, United Kingdom
Received 16 June 2000 / Accepted 28 July 2000
Abstract.
Regulation of malate synthase (MS) and isocitrate lyase (ICL) gene at the posttranscriptional level was studied using actinomycin D, a transcription inhibitor. Detached roots which contained an abundance of NIS and ICL transcripts due to starvation for 4 days, showed a decrease in mRNA amount of about 50% after 3 h incubation in the presence of 10 ug/mI actinomycin D. In contrast, when sucrose was added together with actinomycin D, MS and ICL mRNA decreased to a much lower level within 3 h. Therefore, NIS and ICL half lives appear much shorter in the presence of sugar. Similar results were obtained with detached cotyledons. Confirmation that actinomycin D had effectively stopped transcription was obtained by showing that it prevented light induced expression of hydroxypyruvate reductase and rubisco genes in cotyledons. Thus, NIS and ICL genes appear to be regulated by sugars at the levels of transcription and mRNA stability.
Keywords: Actinomycin D, cucumber (Cucumis sativus), gene expression, glyoxylate cycle, mRNA stability
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