Transcriptional regulation by a circadian rhythm.

Abstract

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. ! 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.

Expression of cab Genes in Douglas-Fir Is Not Strongly Regulated by Light

“…The outlying peak during the continuous dark period may be an anomally. However, erratic fluctuations and somewhat higher levels of psbA expression during dark phases have also been found in tomato (16 (19). Our study showed that diurnal fluctuations of the steady-state cab mRNA in Douglas-fir were relatively minor and the fluctuations that occurred did not appear to be highly influenced by factors associated with photoperiodicity.…”

Dark and Circadian Regulation of mRNA Accumulation in the Short-Day Plant Pharbitis nil

“…In the majority of studies of circadian-regulated gene expression in plants, light rather than darkness is the extemal signal influencing the amplitude of cycling mRNA levels (Guilano et al, 1988;Taylor, 1989). Indeed, darkness was observed to have a negative effect on the amplitude (Guilano et al, 1988) and transcriptional regulation of expression (Taylor, 1989) of Cab genes in tomato and maize, respectively.…”

“…Recently, it has been recognized that circadian rhythms regulate expression of a number of light-regulated plant genes, notably nuclear-encoded photosynthetic genes, and in certain cases, this regulation occurs at the leve1 of gene transcription (Kloppstech, 1985;Piechulla and Gruissem, 1987;Guilano et al, 1988;Nagy et al, 1988;Piechulla, 1988;Meyer et al, 1989;Taylor, 1989;Millar and Kay, 1991). Phase shifting by red light or temperature of the circadian rhythm of cycling mRNA levels has also been reported, strongly suggesting control of gene expression by the biological clock (Tavladoraki et al, 1989;Piechulla and Riesselmann, 1990).…”

Tansley Review No. 37 Circadian rhythms: their origin and control

“…Those which have been studied extensively include the rhythms of carbon dioxide metabolism in the succulent plant Bryophyllum fedtschenkoi {Wilkins, 1959{Wilkins, , 1983{Wilkins, , 1989{Wilkins, , 1991, of luminescence in the photosynthetic, armoured, marine dinoflagellate Gonyaulax polyedra (Sweeney, 1971;Johnson & Hastings, 1986;Roenneberg, Colfax & Hastings, 1989;Morse, Fritz & Hastings, 1990), of leaf movement in the runner bean Phaseolus multiflorus (coccineus) (Biinning, 1973), Albizza julibrissin and Sanianea saman (Satter & Galston, 1981 ;Satter et al, 1988), of conidiation in the fungus Neurospora crassa (Sargent, Briggs & Woodward, 1966;Feldman, Gardner & Denison, 1979;Techel ei al., 1990), and of photosynthetic capacity in the alga Acetabularia mediterranaea (Sweeney & Haxo, 1961 ;Sweeney, TofBi & Rubin, 1967;Schweiger & Schweiger, 1977;Schweiger, Hartwig & Schweiger, 1986). A number of recent studies report a rhythm in the synthesis of the chlorophyll alb pigment-protein complex of photosystem H in a wide variety of plants (Taylor, 1989). Circadian rhythms also occur in animals as diverse as the fruit fly (Drosophila), lizards (Lacerta), hamsters (Mesocricetus) and man (Bunning, 1973;Brady, 1982).…”

“…LTnder light/dark conditions the level of nitrate reductase gene expression shows a diurnal rhythm in tomato and tobacco, but it has not yei: been established whether this rhythm is circadian and persists in constant environmental conditions. Taylor (1989) has shown that transcription of genes coding for the lightharvesting Chi a/b apoprotein exhibits circadian rhythmicity which is superimposed on other regulatory mechanisms in Zea mays. The rhythm was monitored through in vitro transcription in isolated maize leaf nuclei, and it persisted in continuous light but not in darkness.…”