Genetic transformation in higher plants

TLDR

Agrobacterium tumefaciens transfers T‑DNA from its Ti plasmid into plant nuclear DNA, enabling successful plant cell transformation. The study discusses the needs and possibilities for developing alternate vectors and transformation procedures. Modified Agrobacterium strains lacking pathogenicity genes, intermediate vectors with selectable markers, and efficient in vitro methods allow the Ti plasmid system to transform plant cells. These modifications produce a simple, efficient, reproducible system that yields morphologically normal, stably transformed plants with heritable foreign genes, facilitating gene expression studies and potential agronomic crop improvement.

Abstract

Successful transformation of plant cells has been obtained utilizing vectors and DNA delivery methods derived from the plant pathogen, Agrobacterium tumefaciens. This soil bacterium is capable of transferring a DNA segment (T‐DNA), located between specific nucleotide border sequences, from its large tumor inducing (Ti) plasmid into the nuclear DNA of infected plant cells. The exploitation of the Agrobacterium/Ti plasmid system for plant cell transformation has been facilitated by (1) the construction of modified Agrobacterium strains in which the genes responsible for pathogenicity have been deleted; (2) the design of intermediate vectors containing selectable drug markers for introducing foreign genes into the Ti plasmid and subsequently into plant cells; and (3) the development of efficient in vitro methods for transforming plant cells and tissues with engineered Agrobacterium strains. These modifications have led to the development of a simple, efficient, and reproducible transformation system from which morphologically normal transformed plants can be readily regenerated. The foreign genes are stably maintained and expressed in the resulting plants and are inherited by progeny as typical Mendelian traits. The availability of transformation systems has already facilitated numerous studies on gene expression and regulation in plants and should eventually allow for the modification of various crop species in an agronomically significant manner. The needs and possibilities for the development of alternate vectors and transformation procedures will be discussed.