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  • Title: Identification of DNA sequences controlling light- and chloroplast-dependent expression of the lhcb1 gene from Chlamydomonas reinhardtii.
    Author: Hahn D, Kück U.
    Journal: Curr Genet; 1999 Jan; 34(6):459-66. PubMed ID: 9933357.
    Abstract:
    In Chlamydomonas reinhardtii, expression of the lhcb1 gene encoding a chlorophyll-a/b-binding protein of photosystem II is highly regulated by light, inhibitors of chlorophyll synthesis, as well as by circadian rhythms. In light/dark synchronized cultures, the rapid increase of lhcb1 mRNA levels during the light phase is regulated primarily at the transcriptional level. We have used the arylsulphatase (ars) reporter gene to analyze the lhcb1 5' upstream sequences for the presence of light-responsive elements. In transformants carrying chimeric reporter genes, accumulation of lhcb1/ars mRNA is markedly stimulated by light, with a time course similar to that of transcripts from the endogenous lhcb1 gene. Promoter deletion studies revealed that a 255-bp fragment of the lhcb1 5' upstream region is sufficient to confer proper light regulation on the promoterless ars gene. Moreover, the region between positions -255 and -122 with respect to the start site of translation were found to contain one or more light-responsive elements. Strikingly, these sequences also seem to be involved in chloroplast-dependent lhcb1 gene expression as indicated by Northern analyses of transformants with photo-oxidatively damaged chloroplasts. This suggests that both light- and chloroplast-dependent expression of the lhcb1 gene are mediated by the same cis-acting elements.
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