Gene transfer to plants via particle bombardment

Abstract

Approximately six years ago, Klein et al.described a procedure in which high velocity microprojectiles were utilized to deliver nucleic acids into living cells [1]. In those experiments, transient expression of exogenous RNA or DNA was demonstrated in epidermal cells of onion (Allium cepa). Following these experiments, the technique of particle bombardment (otherwise known as biolistics, microprojectile bombardment, particle acceleration etc.) has been shown to be the most versatile and effective way for the creation of many transgenic organisms, including microorganisms, mammalian cells, and a large number of plants species. Tables 1 and 2 provide a comprehensive listing of microorganisms and plant species, respectively, that have been successfully engineered using particle bombardment technology. An estimated two hundred papers have been published on various aspects of the technique, including a number of comprehensive reviews [2–4]. Several advantages make micro-projectile bombardment the method of choice for engineering crop species : a) Transformation of organized tissue: The ability to engineer organized and potentially regenerable tissue permits introduction of foreign genes into elite germplasm. b) Universal delivery system: Transient gene expression has been demonstrated in numerous tissues representing many different species. In particular cases in which recovery of transgenic plants has not been reported, this deficit is more due to the lack of a favorable tissue culture response than the DNA delivery method. c) Transformation of recalcitrant species: Engineering of important agronomic crops such as soybean, cotton, maize, rice, etc. has been restricted to a few non-commercial varieties when conventional methods are used. Particle bombardment technology allowed recovery of transgenic plants from many commercial cultivars. d) Study of basic plant development processes: By utilizing chromogenic markers it is possible to study developmental processes and also clarify the origin of germline in regenerated plants.