A clock- and light-regulated gene that links the circadian oscillator to LHCB gene expression.
We have identified and characterized a novel tobacco gene, called ZGT (from the Chinese phrase zhong guang tiaokong, or clock and light controlled), that is regulated by the circadian clock and light. ZGT transcripts have alternate forms that are differentially expressed in different tissues. ZGT is expressed rhythmically in light/dark cycles and in constant light. Constitutive expression of ZGT sustains the expression of the clock-controlled LHCB1*1 gene in constant darkness, when it would normally dampen, but does not affect LHCB1*1 expression in constant light. ZGT expression is induced rapidly by light, and overexpression of ZGT increases the sensitivity of the circadian oscillator to brief light pulses. The ZGT promoter includes a G-box motif that is found in many light-regulated promoters in plants and is the same as the E box described for rhythmically regulated promoters of animal circadian clock genes. The ZGT promoter also includes "evening element" motifs that are correlated with circadian control of plant genes. We postulate that light- and clock-regulated expression of ZGT acts as a coupling agent between the central circadian oscillator and rhythmic LHCB1*1 expression and that it may function as a component in plant phototransduction pathways.
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Department of Biological Sciences, Box 1812-B, Vanderbilt University, Nashville, Tennessee 37235, USA.
Johnson
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D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana
D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; C432431:ZGT protein, Nicotiana tabacum