Agrobacteria-Mediated Gene Transformations and Vectors for Gene Cloning in Plants

Abstract

This chapter considers the major groups of gene vectors for plants, the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens, the caulimo viruses, and the Gemini viruses. Crown gall disease is the infection inflicted mainly on young fruit trees by Agrobacterium tumefaciens. Plant transformation vectors based on Agrobacterium can generally be divided into two categories: those that cointegrate into a resident Ti plasmid and those that replicate autonomously. Ti plasmids have been studied in detail using molecular techniques such as restriction mapping and insertional mutagenesis. Cointegrating transformation vectors must include a region of homology between the vector plasmid and the Ti plasmid. This requirement for homology means that the vector is capable of integrating into a limited number of Ti plasmids. Several requirements must be considered in the development of a truly useful selectable marker system. It is most critical that the selective agent be inhibitory to plant cells.