Identifier

etd-04132005-091358

Degree

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

Document Type

Dissertation

Abstract

Sheath blight caused by the fungal pathogen fungus Rhizoctonia solani Kuhn, is an economically important disease of rice in the southern United States. The overall goal of this study was to identify proteins that were affected by sheath blight development by comparing protein expression patterns between the susceptible, wild-type cultivar Labelle and the resistant, mutant line LSBR-5. Protein samples were extracted from inoculated and non-inoculated rice leaf sheaths after 24 hrs and then loaded onto a Bio-Rad 2-DE gel system. Approximately 1,000 protein spots stained with Sypro-Ruby were reproducibly resolved in all gels used in the comparison analysis. The comparison analysis of relative abundances of protein spots between inoculated and non-inoculated samples was carried out with PDQUEST image analysis software. With MS/MS spectra produced by ESI-Q-TOF analysis, 27 out of a total of 36 protein spots were identified through NCBI nr and NCBI EST database searching with Mascot MS/MS Ion Search Engines (Matrix Sciences). Twenty two protein spots were detected in response to inoculation of both susceptible and resistant plants where 21 protein spots were up-regulated and 1 protein spot was down- regulated. Sixteen of the 22 proteins were identified. The presumed functions of the identified proteins were related to antifungal activity, energy metabolism, photosynthesis, protein degradation, and antioxidation. Eight of 16 identified proteins showed higher expression ratios in the inoculated LSBR-5 than in the inoculated Labelle. An additional 14 protein spots were detected in the response of the resistant LSBR-5. Eleven of 14 protein spots were identified with presumed functions relating to antifungal activity, signal transduction, energy metabolism, photosynthesis, molecular chaperone, protein degradation, and antioxidation. This study is the first to monitor protein expression patterns of the rice leaf-sheath responding to challenge by R. solani and to detect response differences between resistant mutant and susceptible parental material. The information and detected proteins in this study will serve as a solid foundation for future studies to elucidate induced defense mechanisms of rice when infected with R. solani.

Date

2005

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

James Oard

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