THE PLANT CELL, Vol 1, Issue 2 259-264, Copyright © 1989 by American Society of Plant Biologists
Transcriptional Regulation by a Circadian Rhythm
W. C. Taylor
Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, G.P.O. Box 1600, Canberra, A.C.T., 2601, Australia
Transcription of genes encoding the light-harvesting chlorophyll a/b
protein (Cab) was shown previously to be regulated by light and a number of
developmental factors. I show that a circadian rhythm in transcriptional
activity is superimposed on these other regulatory programs. In vitro
transcription measurements in isolated maize leaf nuclei demonstrated that
changes in transcription are not coincident with light-dark transitions and
that diurnal changes in transcription continue in continuous light and
disappear in complete darkness. Light intensity influences the amplitude of
transcriptional changes but has no effect on periodicity. Major diurnal
changes in Cab mRNA are evident not only in developing seedling leaves, but
also in mature, fully expanded leaves. Genes encoding phosphoenolpyruvate
carboxylase and the cytosolic form of aldolase show no diurnal changes in
transcription.