A biolistic method for high-throughput production of transgenic wheat plants with single gene insertions.

BACKGROUND: The relatively low efficiency of biolistic transformation and subsequent integration of multiple copies of the introduced gene/s significantly complicate the genetic modification of wheat (Triticum aestivum) and other plant species. One of the key factors contributing to the reproducibility of this method is the uniformity of the DNA/gold suspension, which is dependent on the coating procedure employed. It was also shown recently that the relative frequency of single copy transgene inserts could be increased through the use of nanogram quantities of the DNA during coating. RESULTS: A simplified DNA/gold coating method was developed to produce fertile transgenic plants, via microprojectile bombardment of callus cultures induced from immature embryos. In this method, polyethyleneglycol (PEG) and magnesium salt solutions were utilized in place of the spermidine and calcium chloride of the standard coating method, to precipitate the DNA onto gold microparticles. The prepared microparticles were used to generate transgenics from callus cultures of commercial bread wheat cv. Gladius resulting in an average transformation frequency of 9.9%. To increase the occurrence of low transgene copy number events, nanogram amounts of the minimal expression cassettes containing the gene of interest and the hpt gene were used for co-transformation. A total of 1538 transgenic wheat events were generated from 15,496 embryos across 19 independent experiments. The variation of single copy insert frequencies ranged from 16.1 to 73.5% in the transgenic wheat plants, which compares favourably to published results. CONCLUSIONS: The DNA/gold coating procedure presented here allows efficient, large scale transformation of wheat. The use of nanogram amounts of vector DNA improves the frequency of single copy transgene inserts in transgenic wheat plants.

Esquemas conservativos basados en el método de separación para la simulación numérica de vórtices en la atmósfera / Conservative splitting based schemes for numerical simulation of vortices in the atmosphere

Se propone un nuevo método para la construcción de esquemas en diferencias finitas para el modelo de aguas someras en un canal periódico sobre el plano y sobre la esfera. La ventaja principal de los esquemas consiste en que ellos conservan exactamente la masa y la energía total del sistema. El enfoque está basado en la separación del operador del modelo por coordenadas y por procesos físicos. Como resultado, la solución del problema original se reduce a la solución de problemas simples unidimensionales. Se propone un conjunto de tales esquemas, que son lineales o no lineales dependiendo de la especificación de parámetros del esquema. A diferencia de los métodos conocidos, este enfoque permite derivar esquemas numéricos conservadores después de hacer discreto el problema original tanto en tiempo como en espacio. Además, los algoritmos numéricos utilizados para calcular la solución son económicos desde el punto de vista computacional, ya que cada esquema se realiza rápida y fácilmente usando un método directo, sin iteraciones

Air quality assessment and control of emission rates.

Mathematical methods based on the adjoint model approach are given for the air-pollution estimation and control in an urban region. A simple advection-diffusion-reaction model and its adjoint are used to illustrate the application of the methods. Dual pollution concentration estimates in ecologically important zones are derived and used to develop two non-optimal strategies and one optimal strategy for controlling the emission rates of enterprises. A linear convex combination of these strategies represents a new sufficient strategy. A method for detecting the enterprises, which violate the emission rates prescribed by a control, is given. A method for determining an optimal position for a new enterprise in the region is also described.