title: Circadian regulation of chloroplastic f and m thioredoxins through control of the CCA1 transcription factor.
abstract: Chloroplastic thioredoxins f and m (TRX f and TRX m) mediate light regulation of carbon metabolism through the activation of Calvin cycle enzymes. The role of TRX f and m in the activation of Calvin cycle enzymes is best known among the TRX family. However, the discoveries of new potential targets extend the functions of chloroplastic TRXs to other processes in non-photosynthetic tissues. As occurs with numerous chloroplast proteins, their expression comes under light regulation. Here, the focus is on the light regulation of TRX f and TRX m in pea and Arabidopsis during the day/night cycle that is maintained during the subjective night. In pea (Pisum sativum), TRX f and TRX m1 expression is shown to be governed by a circadian oscillation exerted at both the transcriptional and protein levels. Binding shift assays indicate that this control probably involves the interaction of the CCA1 transcription factor and an evening element (EE) located in the PsTRX f and PsTRX m1 promoters. In Arabidopsis, among the multigene family of TRX f and TRX m, AtTRX f2 and AtTRX m2 mRNA showed similar circadian oscillatory regulation, suggesting that such regulation is conserved in plants. However, this oscillation was disrupted in plants overexpressing CCA1 (cca1-ox) or repressing CCA1 and LHY (cca1-lhy). The physiological role of the oscillatory regulation of chloroplastic TRX f and TRX m in plants during the day/night cycle is discussed.
authors.affiliation: Estación Experimental del Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain.
authors.forename: Juan de Dios
authors.initials: Jde D
authors.lastname: Barajas-López
authors.forename: Antonio Jesus
authors.initials: AJ
authors.lastname: Serrato
authors.forename: Roland
authors.initials: R
authors.lastname: Cazalis
authors.forename: Yves
authors.initials: Y
authors.lastname: Meyer
authors.forename: Ana
authors.initials: A
authors.lastname: Chueca
authors.forename: Jean Philippe
authors.initials: JP
authors.lastname: Reichheld
authors.forename: Mariam
authors.initials: M
authors.lastname: Sahrawy
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D054479:Chloroplast Thioredoxins / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D002940:Circadian Rhythm; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D005966:Glucuronidase; D018532:Pisum sativum / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C114425:CCA1 protein, Arabidopsis; D054479:Chloroplast Thioredoxins; D012333:RNA, Messenger; D014157:Transcription Factors; D005966:Glucuronidase