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You searched for +publisher:"Texas A&M University" +contributor:("Cook, Douglas R."). One record found.

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Texas A&M University

1. Pedro, Uribe Mejia. Dissection of defense responses of skl, an ethylene insensitive mutant of Medicago truncatula.

Degree: 2004, Texas A&M University

The interactions between Medicago truncatula and Phytophthora medicaginis were examined using skl, a mutant blocked in ethylene perception, and a range of wild accessions of this plant species. P. medicaginis infection of M. truncatula plants resulted in compatible responses, whereas the mutant genotype was found to be hyper-susceptible to the pathogen. Phytophthora reproduction and colonization rates of Medicago tissues supported this conclusion. Infection of skl with different pathogens reinforced this observation. Ethylene production in infected A17 and skl roots showed reduced ethylene evolution in the mutant and suggested that a positive feedback loop, known as autocatalytic ethylene production, amplified the ethylene signal. To complement the study, expression analyses of defense response genes in this interaction were studied by real time RTPCR of Phytophthora-infected and mock-infected roots. The genes analyzed were PAL, CHS, IFR, ACC oxidase, GST, and PR10. The sequences needed for the analysis were found through the scrutiny of the M. truncatula EST database employing phylogenetics and bio-informatics tools. In A17 all the genes studied were up-regulated, although the specific gene expression patterns differed. The comparison of gene expression between A17 and skl genotypes allowed the differentiation between ethylene-dependent and ethylene-independent responses. Discrete results showed that ACC oxidase homologues were downregulated in the ethylene perception mutant, corroborating the ethylene observations. However, the expression of genes involved in the phenylpropanoid metabolism was increased in skl relative to A17, suggestive of an antagonism between the ethylene perception pathway and the regulation of the phenylpropanoid pathway. This result implied that Medicago phytoalexins accumulate in the disease interaction, but raised questions about their role in resistance to Phytophthora infection. This study establishes a link between mechanisms that regulate symbiotic infection and the regulation of disease resistance to Oomycete pathogens, especially P. medicaginis. The results served to identify a series of Phytophthora-induced genes, which remain pathogen-responsive even in the absence of a functional ethylene perception pathway. While it is possible that the products of these genes are involved in resistance to P. medicaginis, the present results demonstrate that ethylene perception is required for resistance. Advisors/Committee Members: Kenerley, Charles M. (advisor), Cook, Douglas R. (advisor), Starr, James L. (committee member), McKnight, Thomas D. (committee member).

Subjects/Keywords: Plant-Pathogen Interactions; Legume-Microbe Interactions; Medicago truncatula skl mutation; Ethylene insensitivity; Oomycetes-Phytophthora medicaginis; transcription profiling; Expressed Sequence Tags; Real Time PCR

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APA (6th Edition):

Pedro, U. M. (2004). Dissection of defense responses of skl, an ethylene insensitive mutant of Medicago truncatula. (Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/1241

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Pedro, Uribe Mejia. “Dissection of defense responses of skl, an ethylene insensitive mutant of Medicago truncatula.” 2004. Thesis, Texas A&M University. Accessed October 22, 2019. http://hdl.handle.net/1969.1/1241.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Pedro, Uribe Mejia. “Dissection of defense responses of skl, an ethylene insensitive mutant of Medicago truncatula.” 2004. Web. 22 Oct 2019.

Vancouver:

Pedro UM. Dissection of defense responses of skl, an ethylene insensitive mutant of Medicago truncatula. [Internet] [Thesis]. Texas A&M University; 2004. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/1969.1/1241.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Pedro UM. Dissection of defense responses of skl, an ethylene insensitive mutant of Medicago truncatula. [Thesis]. Texas A&M University; 2004. Available from: http://hdl.handle.net/1969.1/1241

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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