Christopher A Helliwell

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The nucleotide sequences of several animal, plant and bacterial genomes are now known, but the functions of many of the proteins that they are predicted to encode remain unclear. RNA interference is a gene-silencing technology that is being used successfully to investigate gene function in several organisms--for example, Caenorhabditis elegans. We discuss(More)
RNA polymerase III (Pol III) as well as Pol II (35S) promoters are able to drive hairpin RNA (hpRNA) expression and induce target gene silencing in plants. siRNAs of 21 nt are the predominant species in a 35S Pol II line, whereas 24- and/or 22-nucleotide (nt) siRNAs are produced by a Pol III line. The 35S line accumulated the loop of the hpRNA, in contrast(More)
A library containing approximately 40,000 small RNA sequences was constructed for Brassica napus. Analysis of 3025 sequences obtained from this library resulted in the identification of 11 conserved miRNA families, which were validated by secondary structure prediction using surrounding sequences in the Brassica genome. Two 21 nt small RNA sequences reside(More)
Vernalization, the promotion of flowering in response to low temperatures, is one of the best characterized examples of epigenetic regulation in plants. The promotion of flowering is proportional to the duration of the cold period, but the mechanism by which plants measure time at low temperatures has been a long-standing mystery. We show that the(More)
The recovery of information from indirect measurements takes different forms depending on the sophistication with which the process being researched can be modelled mathematically. The forms range from (1) the historical and classical inverse problems regularization situation where explicit models which guaranteed existence and uniqueness have been(More)
Small interfering RNAs (siRNAs) and microRNAs (miRNAs) are non-coding regulatory RNAs that play an important role in development and genome stability in plants. Conventional cloning and sequencing approaches have identified hundreds of miRNAs and a large number of siRNAs, but are no longer the best choices for identification of new miRNAs which are(More)
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