Poster: Plant Pathogen/Symbiont Interactions

Abs # 766: Expression of two isoforms of the antifungal protein osmotin from a cotton gene cluster

Presenter:	Pirtle, Robert M., pirtle@unt.edu
Authors	Pirtle, Robert M. (A)   Wilkinson, Jeffery R. (A)   Spradling, Kimberly D. (A)   Yoder, David W. (A)   Pirtle, Irma L. (A)
Affiliations:	(A): University of North Texas

Pathogenesis-related (PR) proteins are naturally produced by plants in response to environmental stress signals, such as pathogen invasion, drought, and wounding. PR5 proteins called osmotins are thought to possibly interact with membrane receptor proteins in fungal cells and subvert signal transduction pathways, causing osmotic rupture of the fungal cells. Tobacco osmotin genes, expressed in bacteria and resistant yeast strains, have been shown by other labs to encode polypeptide products that kill many fungal species. To study osmotin gene function and expression in cotton, genomic libraries were screened with a tobacco osmotin gene probe. A cotton genomic segment of 30 kb was found to encompass a cluster of two actual osmotin genes and two osmotin pseudogenes. The two genes are almost identical, with coding regions of 729 bp without introns, and would generate putative preproteins of 242 amino acids. To demonstrate functional expression of the two genes, osmotin proteins have been isolated from cotton plant extracts for Western blot analysis with an anti-osmotin polyclonal antibody preparation. The two osmotin fusion proteins have been expressed in a bacterial expression system to evaluate the effectiveness of the cotton osmotins against fungal and bacterial pathogens. The two osmotin genes have also been inserted into a modern binary vector under the control of a 35S CaMV promoter for transformation of Arabidopsis plants and cotton plants, in order to produce transgenic plants overexpressing the osmotins. This research is supported by Cotton Incorporated, Texas State Support Program Agreement 01-897TX, and University of North Texas Organized Research Funds.