Alternative splicing of the maize Ac transposase transcript in transgenic sugar beet (Beta vulgaris L.)

The maize Activator/Dissociation (Ac/Ds) transposable element system was introduced into sugar beet. The autonomous Ac and non-autonomous Ds element excise from the T-DNA vector and integrate at novel positions in the sugar beet genome. Ac and Ds excisions generate footprints in the donor T-DNA that support the hairpin model for transposon excision. Two complete integration events into genomic sugar beet DNA were obtained by IPCR. Integration of Ac leads to an eight bp duplication, while integration of Ds in a homologue of a sugar beet flowering locus gene did not induce a duplication. The molecular structure of the target site indicates Ds integration into a double strand break. Analyses of transposase transcription using RT–PCR revealed low amounts of alternatively spliced mRNAs. The fourth intron of the transposase was found to be partially misspliced. Four different splice products were identified. In addition, the second and third exon were found to harbour two and three novel introns, respectively. These utilize each the same splice donor but several alternative splice acceptor sites. Using the SplicePredictor online tool, one of the two introns within exon two is predicted to be efficiently spliced in maize. Most interestingly, splicing of this intron together with the four major introns of Ac would generate a transposase that lacks the DNA binding domain and two of its three nuclear localization signals, but still harbours the dimerization domain

Modelling sugarcane production systems - II: Analysis of system performance and methodology issues

This paper demonstrates the capability of the model, APSIM-Sugarcane to analyse system performance, by consideration of crop production and related issues for two contrasting sugarcane production systems in northern Australia. Daily output data from short-term model runs are used to demonstrate the capability of the model to represent the diverse management of sugarcane crops encountered in Australia. Output from longer term simulations is used to investigate a number of 'real life' sustainability issues, including an assessment of the production risk associated with season to season climate variability at each site, and the long-term implications of crop residue management on system performance. The paper also develops guidelines for methodological issues in long-term simulations of sugarcane production systems, relating to (1) the length of the climate record necessary to capture the 'true' season to season variability, (2) the need or otherwise to simulate each crop class (i.e. plant and ratoon crops) over the full climate record, and (3) the impact of initial soil conditions on the time for the system to reach a state ol: equilibrium. Results from statistical tears comparing pairs of distributions for various simulation run lengths, identified significant differences for run lengths up to 40 years. This suggests that, while adequate for most scenarios, the current practice of basing sugarcane simulations on 40 years' climate data will not always capture the true season to season variability in response to climate. Results showed that variability associated with season to season climate by management interactions can be adequately captured in a single model run comprised of consecutive crop cycles, without the need to represent every crop class in every year. These findings have the potential to significantly improve modelling efficiency by reducing model run times, simplifying the analysis of model output and, reducing the required computer storage space. Results from long-term simulations, for some model output variables, indicate there is likely to be an initial period of 'settling in' of between 5 and 10 years as the model approaches a state of equilibrium, during which the response of certain model variables will be 'abnormal' and should be used with caution or discarded. (C) 2000 Elsevier Science B.V. All rights reserved

Insertion torque values and success rates for paramedian insertion of orthodontic mini-implants : A retrospective study.

Objectives Orthodontic mini-implants (OMIs) are a reliable method to provide temporary orthodontic anchorage. We hypothesized that there is an optimal insertion torque (10 Ncm) will decrease the success rate and increase palatal OMI failure was rejected