Agrobacterium rhizogenes Mediated Hairy Root Cultures: A Promising Approach for Production of Useful Metabolites

Abstract The production of secondary metabolites through hairy root cultures has proven its importance by its escalating commercial relevance. In the present era hairy root cultures are good alternatives for the production of secondary metabolites, especially for the possibility of altering the formation of bioactive plant metabolites. Hairy roots are differentiated cultures of transformed roots which are developed by the infection of wounded higher plants with Agrobacterium rhizogenes and are an exceptional source of advantageous metabolites with high medicinal value for drug development. A. rhizogenes is the bacterium which induces the hairy-root disease in higher plants. Due to the infection of this bacterium plant cells show neoplastic growth that further differentiates to form “hairy roots.” These neoplastic roots possess high growth rates and genetic stability. A higher level of secondary metabolites (in comparison with the naturally growing plant) can be produced by these genetically transformed root cultures. Genetically transformed roots have the ability to regenerate the whole plant as a transgenic or clone. As a consequence hairy roots have been extensively used as a transgenic tool for the production of metabolites and for gene function studies in plants. Transgenic root systems are also useful for the introduction of a new gene and T-DNA, which is useful for the alteration of metabolic pathways and the production of compounds of interest, that is, pharmaceutically important metabolites. This chapter describes the function of rol genes in T-DNA transfer in the plant genome. This chapter also provides an up-to-date overview of hairy root culture and its applications, which mainly focus on secondary metabolite production.