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item Klessig, D
item Kumar, D
item Chandok, M
item Slaymaker, D
item Clark, D
item Ytterberg, J
item Van Wiyk, K
item Navarre, Duroy - Roy

Submitted to: International Congress of Plant Molecular Biology
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2003
Publication Date: 6/23/2003
Citation: Klessig, D., Kumar, D., Chandok, M., Slaymaker, D., Clark, D., Ytterberg, J., Van Wiyk, K., Navarre, D.A. 2003. Key enzymes in SA- and NO-mediated signal transduction in plant disease resistance. International Congress of Plant Molecular Biology. S:09-1.

Interpretive Summary:

Technical Abstract: Studies during the past decade have rigorously established that salicylic acid (SA) plays a critical, multifaceted role in plant disease resistance. To help elucidate the mechanisms of SA action, we have recently identified several other tobacco proteins besides catalase and ascorbate peroxidase which interact with SA. They include the chloroplastic SABP3, which is carbonic anhydrase. It also has antioxidant activity and plays a role in the hypersensitive resistance response (HR). SABP2, which has high affinity for SA, has been purified and its encoding gene cloned. SABP2 is a lipase, whose activity is enhanced by SA binding. Its expression is induced by infection and its silencing suppresses resistance to TMV and development of systemic acquired resistance. Nitric Oxide, which is a critical signal in animal innate immunity, also appears to participate in plant disease resistance. Several critical players of NO signaling in animals are also operative in plants including guanylate cyclase, aconitases, and the second messengers cGMP, cADP ribose and Ca2+. We have now identified the enzyme responsible for the dramatic rise in NO synthesis following pathogen infection of resistant, but not susceptible, tobacco and Arabidopsis. The protein was purified ~33,000 fold and corresponds to a variant form of the P protein of the glycine decarboxylase (GDC). Proof that it is the pathogen-inducible NO synthase (iNOS) of plants is provided by the demonstration that inhibitors of the P protein of GDC block iNOS activity, and that Arabidopsis variant P protein produced in E.coli or baculovirus-infected insect cells has NOS activity. The plant enzyme shares many biochemical properties with animal NOSs. Despite this, only a few of the critical motifs used by animal NOSs for NO production can be recognized in the variant P sequence, suggesting that it uses very different chemistry.