DEVELOPMENT AND OPTIMIZATION OF MICROPROJECTILE SYSTEMS FOR PLANT GENETIC-TRANSFORMATION

The recently developed microprojectile method for gene transfer to intact cells has been successfully used to transform plant species including some which previously resisted attempts using Agrobacterium and protoplast mediated techniques. In addition, microprojectile bombardment has already proved uniquely suitable for other applications including direct transformation of organelle genomes and rapid assessment of transient expression of genetic constructs introduced into cells of intact tissues. Here we describe various microprojectile acceleration devices and the steps necessary to develop an effective microprojectile mediated transformation system for any plant species. We emphasise the need to optimise the delivery of DNA into cells, and to tailor strategies for generating stably transformed plants based on the nature of the target tissue, behaviour in tissue culture, and available marker genes. Patterns of cotransformation and coexpression of introduced genes in stable nuclear transformants generated with microprojectiles are summarised, and other applications including organelle transformation are briefly described. We mention technical limitations to the application of microprojectile-mediated gene transfer which need to be overcome if the method is to achieve its full potential as a near-universal gene transfer technique with exciting applications in basic plant molecular biology and practical plant improvement.