Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/24/2004
Publication Date: 6/30/2004
Citation: Rajasekaran, K. 2004. Benefits of plant biotechnology - Disease resistant crops [abstract]. Biotechnology Symposium, In Memoriam, the Late Dr. Allan E. Zipf, Alabama A&M University, June 4, 2004, Normal, AL.
Technical Abstract: Plants are immobile and also do not possess a complex immunoglobulin-based protection system, such as that found in higher vertebrates, to defend against infective microbial pathogens; however, they do have a wide variety of innate host defense mechanisms at their disposal. These include the production of antimicrobial reactive oxygen species (ROS), secondary metabolites, hydrolytic enzymes, and a wide array of antimicrobial proteins and peptides. However, these defense mechanisms are not adequate and often compromised by the invading microbial pathogens. As a result, crop yields often decrease by 12 to 15 percent on average due to phytopathogens and some of the mycotoxigenic fungi, such as Aspergillus and Fusarium, contaminate food and feed material with toxins. For example, cottonseed is a valuable by-product of the cotton industry with an annual value between 500 and 700 million dollars in the United States. It is used in animal feed and to produce cottonseed oil for human consumption. Both marketability and profitability are greatly diminished when cottonseed that has been infected with toxigenic strains of Aspergillus flavus becomes contaminated with aflatoxin. In our laboratory, we are using genetic engineering to develop cotton with enhanced resistance to A. flavus with the goal of reducing aflatoxin levels in cottonseed. Towards this goal, we have developed cotton transformation and regeneration systems, developed model systems to test the efficacy of potential anti-flavus gene products in vitro and in vivo, identified several potential resistance genes, and evaluated transgenic cottons for resistance to microbial pathogens. We have documented that in addition to increased control of A. flavus in cottonseed, the transgenic cotton and tobacco plants have shown significant resistance to vascular and leaf phytopathogens. The antifungal gene constructs that we have successfully evaluated so far include a bacterial chloroperoxidase (cpo-p) and a linear, amphipathic, synthetic, lytic peptide (D4E1). Details on control of several pathogens (A. flavus, Fusarium verticillioides, Verticillium dahliae, Colletotrichum destructivum, and Thielaviopsis basicola) by transgenic tobacco or cotton, either in vitro or in planta, will be provided. Additional details on our efforts to increase gene expression in a tissue-specific manner will also be provided.