AGROBACTERIUM-TUMEFACIENS TRANSFORMATION OF MONOCOTYLEDONS

Agrobacterium tumefaciens (Smith and Townsend, 1907) has been an extremely useful vector to transfer foreign genes into dicotyledonous plants. Monocotyledonous plants, particularly the cereals, have been considered outside the host range for A. tumefaciens, which has necessitated the development of other transformation systems such as naked DNA delivery to protoplasts and, most recently, microprojectile bombardment delivery of DNA to cells and tissues. Both systems have worked, but there are still many difficulties encountered in routine transformation of any monocotyledon. Recently, there has been renewed interest in using the A. tumefaciens system to transform economically important grasses and other monocotyledons. This paper examines the literature and steps involved in transformation of monocotyledons by A. tumefaciens. The many recent advances in understanding the biology of the infection process (meristematic target cell, vir gene inducing compounds, and wide host range strains of A. tumefaciens), and availability of more monocotyledon gene promoters and improved selectable markers greatly improve the opportunities of developing monocotyledon transformation systems with A. tumefaciens.