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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2007.12.031 Byline: Jeffrey L. Caplan (1), Padmavathi Mamillapalli (1), Tessa M. Burch-Smith (1), Kirk Czymmek (2), S.P. Dinesh-Kumar (1) Keywords: CELLIMMUNO; MOLIMMUNO Abstract: Plant innate immunity relies on the recognition of pathogen effector molecules by nucleotide-binding-leucine-rich repeat (NB-LRR) immune receptor families. Previously we have shown the N immune receptor, a member of TIR-NB-LRR family, indirectly recognizes the 50 kDa helicase (p50) domain of Tobacco mosaic virus (TMV) through its TIR domain. We have identified an N receptor-interacting protein, NRIP1, that directly interacts with both N's TIR domain and p50. NRIP1 is a functional rhodanese sulfurtransferase and is required for N to provide complete resistance to TMV. Interestingly, NRIP1 that normally localizes to the chloroplasts is recruited to the cytoplasm and nucleus by the p50 effector. As a consequence, NRIP1 interacts with N only in the presence of the p50 effector. Our findings show that a chloroplastic protein is intimately involved in pathogen recognition. We propose that N's activation requires a prerecognition complex containing the p50 effector and NRIP1. Author Affiliation: (1) Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA (2) Department of Biological Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, DE 19711, USA Article History: Received 17 April 2007; Revised 18 October 2007; Accepted 12 December 2007 Article Note: (miscellaneous) Published: February 7, 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2005.03.007 Byline: Yule Liu (1), Michael Schiff (1), Kirk Czymmek (2), Zsolt Talloczy (3), Beth Levine (3)(4), S.P. Dinesh-Kumar (1) Abstract: The plant innate immune response includes the hypersensitive response (HR), a form of programmed cell death (PCD). PCD must be restricted to infection sites to prevent the HR from playing a pathologic rather than protective role. Here we show that plant BECLIN 1, an ortholog of the yeast and mammalian autophagy gene ATG6/VPS30/beclin 1, functions to restrict HR PCD to infection sites. Initiation of HR PCD is normal in BECLIN 1-deficient plants, but remarkably, healthy uninfected tissue adjacent to HR lesions and leaves distal to the inoculated leaf undergo unrestricted PCD. In the HR PCD response, autophagy is induced in both pathogen-infected cells and distal uninfected cells; this is reduced in BECLIN 1-deficient plants. The restriction of HR PCD also requires orthologs of other autophagy-related genes including PI3K/VPS34, ATG3, and ATG7. Thus, the evolutionarily conserved autophagy pathway plays an essential role in plant innate immunity and negatively regulates PCD. Author Affiliation: (1) Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520 (2) Department of Biological Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, Delaware 19711 (3) Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York 10032 (4) Department of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390 Article Note: (miscellaneous) Published: May 19, 2005

The resistance gene N of tobacco, which mediates the resistance to the tobacco mosaic virus (TMV), is isolated by transposon tagging. The tagging uses the maize activator transposon, which confers the genomic DNA fragment with an N gene to TMV susceptible tobacco. The plant disease resistance genes identify and combat the invading pathogens by triggering host defense responses. This is performed by the resistance gene N, which encodes the 131.4 kDa protein with an amino acid terminal domain.

P58IPK is a cellular inhibitor of the mammalian double-stranded RNA-activated protein kinase (PKR). Here we provide evidence for the existence of its homolog in plants and its role in viral infection at the organism level. Viral infection of P58IPK-silenced Nicotiana benthamiana and Arabidopsis knockouts leads to host death. This host cell death is associated with phosphorylation of the α subunit of eukaryotic translation initiation factor (eIF-2α). Loss of P58IPK leads to reduced virus titer, suggesting that wild-type P58IPK protein plays an important role in viral pathogenesis. Although our complementation results using mammalian P58IPK suggest conservation of the P58IPK pathway in plants and animals, its biological significance seems to be different in these two systems. In animals, P58IPK is recruited by the influenza virus to limit PKR-mediated innate antiviral response. In plants, P58IPK is required by viruses for virulence and therefore functions as a susceptibility factor. [Copyright &y& Elsevier]