Genetic transformation of plants

Abstract

Current status of the molecular approaches for integrative genetic transformation of plants is reviewed. Agrobacterium-mediated and direct DNA transformation of protoplasts are considered. Elucidation of the molecular events in natural genetic transformation of plant cells in crown gall disease caused by Agrobacterium tumefaciens, has led to the development of T-DNA based vectors for introducing exogenous DNA into plant cells. Various strategies used for this are discussed. So far, Agrobacterium-mediated transformation has been most successful and widely used in dicotyledonous plants. Direct DNA transformation involves either DNA uptake by protoplasts or its mechanical delivery into the cell nucleus. Transformation of both monocotyledonous and dicotyledonous plant cells has been shown by this method. The genes transferred into plants from bacteria, other plant and animal species and various promoters used in chimeric gene constructs for the expression of such genes are listed. Organ specific expression and Mendelian inheritance of transferred genes have been demonstrated. Prospects of the transformation technique for the improvement of crop plants are examined. Gene transfers reported so far indicate that the immediate benefits will be in the development of cultivars carrying herbicide resistance or biocide gene(s). Identification, isolation and cloning of DNA sequences governing resistance to plant diseases or pests, and their introduction into improved cultivars could become possible in the future. Isolation, in vitro modification and re-introduction of the modified gene(s) back into the plant genome is yet another possibility for the future.