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Title: Expression analysis of Arabidopis thaliana cyclin CycD2
Author: Cockcroft, C. E.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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This thesis describes the construction of tobacco lines with ectopic expression of Arabidopsis CycD2 from a constitutive cauliflower mosaic virus 35S promoter and also investigates the endogenous expression pattern of CycD2 in different Arabidopsis tissues. Transgenic tobacco plants overexpressing Arabidopsis CycD2 were found to exhibit accelerated growth phenotypes as measured by height and leaf dimensions. The biomass and leaf surface area of p35S:CycD2 transgenics was significantly greater than wild type seedlings during early vegetative growth for P=0.01 using Student's t-test. The mean height of the transgenics was greater than wild type until later in development after the floral transition although the terminal height of the transgenics is generally not greater than for wild type plants. These transgenics consequently reach floral development earlier than wild type plants, produce flowers which are larger than wild-type and produce an increased seed yield. These effects were shown to be stably inherited and the CycD2-induced growth effect was not observed in transgenics which had lost the insert due to genetic segregation in the next generation. Transgenic tobacco plants overexpressing CycD2 show an acceleration of vegetative development towards maturity but are otherwise phenotypically normal. Transgenics expressing antisense CycD2, do not exhibit enhanced growth rates and are significantly smaller than wild type, produce smaller leaves with altered morphology, and are delayed in the transition from vegetative to floral development. An Arabidopsis thaliana genomic library was screened using the 5' region of CycD2 cDNA as a probe. The isolated genomic clone was characterised and sequenced revealing the structure of CycD2 gene and several putative regulatory elements within the promoter. Translational fusions of pCycD2 to the β-glucuronidase gene (GUS) or green fluorescent protein (GFP) were constructed and introduced into Arabidopsis to investigate the cellular expression pattern of CycD2. The results reveal that CycD2 is expressed in the root and shoot apical meristems and at the site of lateral root emergence. Reporter gene expression is also detected in axillary meristems, developing floral buds and floral organs where strongest expression is in the anthers.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available