Gene gun

The gene gun is a device for injecting cells with genetic information, originally designed for plant transformation. The payload is an elemental particle of a heavy metal coated with plasmid DNA. The actual name of the gene gun is the Biolistic Particle Delivery System, and this technique is often simply referred to as biolistics.

This device is able to transform almost any plant and is not limited to genetic material of the nucleus: It can also transform plastids.

Design

The gene gun was originally a nail gun for concrete surfaces modified to fire tungsten particles. Later the design was greatly refined. Improvements include the use of helium propellant and a multi-disk-collision delivery mechanism. Other heavy metals such as gold and silver are also used, but not as frequently due to reasons of availability and cost.

Conception of the gene gun is accredited to Edward Wolf and Nelson Allen of the Cornell Nanofabrication Facility and Cornell University plant scientists John Sanford and Theodore Klein . The rights to commercial use of the gene gun were sold to DuPont in 1989.

Application

The target of a gene gun is often a callus of undifferentiated plant cells growing on gel medium in a petri dish. After the tungsten particles have impacted the dish, the gel and callus are largely disrupted. However, some cells were not obliterated in the impact, and have successfully enveloped a DNA coated tungsten particle, whose DNA eventually migrates to and integrates into a plant chromosome.

Cells from the entire petri dish can be re-collected and selected for successful integration and expression of new DNA using modern biochemical techniques, such as a using a tandem selectable gene and northern blots.

Selected single cells from the callus can be treated with a series of plant hormones, such as auxins and gibberellins, and each may divide and differentiate into the organized, specialized, tissue cells of an entire plant. This capability of total re-generation is called totipotency. The new plant that originated from a successfully shot cell may have new genetic (heritable) traits.

Using the gene gun may be contrasted with using Agrobacterium tumefaciens and its Ti plasmid to insert genetic information into plant cells. See transformation for different methods of transformation in different species.