title: Robust circadian rhythms of gene expression in Brassica rapa tissue culture.
abstract: Circadian clocks provide temporal coordination by synchronizing internal biological processes with daily environmental cycles. To date, study of the plant circadian clock has emphasized Arabidopsis (Arabidopsis thaliana) as a model, but it is important to determine the extent to which this model applies in other species. Accordingly, we have investigated circadian clock function in Brassica rapa. In Arabidopsis, analysis of gene expression in transgenic plants in which luciferase activity is expressed from clock-regulated promoters has proven a useful tool, although technical challenges associated with the regeneration of transgenic plants has hindered the implementation of this powerful tool in B. rapa. The circadian clock is cell autonomous, and rhythmicity has been shown to persist in tissue culture from a number of species. We have established a transgenic B. rapa tissue culture system to allow the facile measurement and manipulation of clock function. We demonstrate circadian rhythms in the expression of several promoter:LUC reporters in explant-induced tissue culture of B. rapa. These rhythms are temperature compensated and are reset by light and temperature pulses. We observe a strong positive correlation in period length between the tissue culture rhythm in gene expression and the seedling rhythm in cotyledon movement, indicating that the circadian clock in B. rapa tissue culture provides a good model for the clock in planta.
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755-3576, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
authors.forename: Qiguang
authors.initials: Q
authors.lastname: Xie
authors.forename: C Robertson
authors.initials: CR
authors.lastname: McClung
mesh_terms: D001683:Biological Clocks / Q000235:genetics*; D029741:Brassica rapa / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D018548:Cotyledon / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008027:Light; D030821:Plants, Genetically Modified / Q000235:genetics; D013696:Temperature; D046509:Tissue Culture Techniques
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