CAREER: Virus Structure in Plant Resistance

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; R o o t E n t r y F @ @ C o m p O b j b W o r d D o c u m e n t O b j e c t P o o l @ @ F Microsoft Word 6.0 Document MSWordDoc Word.Document.6 ; Oh +' 0 $ H l D h R:\WWUSER\TEMPLATE\NORMAL.DOT jack cohen jack cohen @ d @ @ B e = e D D D D D \ f D C p t t t t t t t S D T ( t t t t t t t p t t t t t t . 6 t t / t Culver 9506849 Plant disease resistance has been widely studied because of its economic importance to agriculture. Much of this effort has focused on the hypersensitive response (HR) conferred by single plant genes. This type of resistance is dependent upon host recognition of the invading pathogen, possibly via plant receptors that specifically bind molecules of pathogen origin, called elicitors. The recent cloning and characterization of several plant resistance genes has been a major breakthrough in the field of plant biology and has added support to the elicitor receptor hypothesis. Future studies defining the molecular interaction between pathogen elicitors and plant resistance genes will be critical in understanding the molecular basis of plant disease resistance and in developing practical ways to utilize this resistance in the field. Using the interaction between the tobamovirus coat protein (CP) and the N' gene HR of Nicotiana sylvestris as a model system, this proposal seeks to molecularly characterize elicitor specificity. Current evidence indicates that CPs with "weaker" quaternary structures act as elicitors of the HR while CPs with "stronger" quaternary structures do not. Identifying the structural motifs required for HR induction will be an important first step in defining putative elicitor receptor interactions. Three objectives will be addressed: 1) identify the form (monomer, dimer, trimer, etc.) of CP that is recognized by the N' gene host; 2) identify a putative receptor binding site within the CP three dimensional structure; 3) investigate structural alterations in CP that allow some tobamoviruses to elude N' gene resistance. An important aspect of this proposal is to provide undergraduate and graduate students with training in both molecular biology and protein biophysical studies. The wide range of scientific matters involved in this investigation provide an ideal interdisciplinary "training matrix" for students interested in research careers. Students will learn the skills needed to manipulate protein sequences (gene cloning, site specific mutagenesis, etc.), determine the biophysical consequences of those manipulations (analytical ultracentrifugation, circular dichroism, and electron microscopy), and relate these changes to biological function (virion structure and plant resistance). In addition to technical skills, students will organize and present their research at a planned yearly miniconference. %%% Plant disease resistance has been widely studied because of its economic importance to agriculture. Much of this effort has focused on the hypersensitive response (HR) conferred by single plant genes. This type of resistance is dependent upon host recognition of the invading pathogen, p ossibly via plant receptors that specifically bind molecules of pathogen origin, called elicitors. The recent cloning of several plant resistance genes has added support to the elicitor receptor hypothesis. Using the interaction between the tobamovirus coat protein (CP) and the N' gene HR of Nicotiana sylvestris as a model system, this proposal seeks to molecularly characterize elicitor specificity. Specifically, what makes one pathogen elicit a resistance response while another does not? Three objectives will be addressed: 1) identify the form (monomer, dimer, trimer, etc.) of CP that is recognized by the N' gene host; 2,1 identify and analyze the putative receptor binding site within the CP three dimensional structure; 3) investigate the structural differences between CPs that allow some tobamoviruses to elude N' gene resistance. Information from this study will be important to understanding the molecular basis of plant disease resistance and in developing practical ways to more fully utilize this resistance in the field. *** @ ....()()))()() ; S u m m a r y I n f o r m a t i o n (