Plants exhibit natural resistance to diseases through systems of gene-for-gene interactions. Pathogens express genes called avirulence genes (Avr) that interact with plant encoded resistance genes (R). One example of such an interaction is between the tobacco N gene that encodes resistance to tobacco mosaic virus (TMV). Another is the RCY1 gene of Arabidopsis, which encodes resistance to cucumber mosaic virus-Y (CMV-Y). In fact, many avirulence and resistance genes have been identified in recent years, yet little is known about the mechanism of resistance. Pathologically, resistance is characterized by a hypersensitive response that results in massive cell death, but restricts propagation of the virus. The structure of many of resistance proteins suggests that the responses may activate signaling pathways. This proposal will use an Arabidopsis thaliana genetic system to study both the N/TMV and Rcy1/CMV-Y systems. Expression in Arabidopsis of the Avr protein of TMV (p50 helicase) in N- expressing cells or CMV-Y coat protein (CP) in Rcy1-expressing cells during germination of seedlings causes rapid death of the developing plant. This provides a genetic selection for plant mutants that fail to respond to the Avr protein, potentially identifying proteins downstream of the resistance genes. The proposal has 7 Specific Aims. The first three address the identity of cellular components that make up the response system to the two pathogens.
Aim 1 will attempt to identify mutations that affect components of the pathway, both loss and gain-of- function mutations. In addition, yeast two and three-hybrid approaches and biochemical approaches (co-purification, affinity chromatography or interaction cloning) will also be used to identify proteins that interact with the resistance proteins.
Aim 2 will identify genes whose expression is altered during response to pathogens and Aim 3 will test whether known genes affecting other gene-for-gene responses also affect the two being studied here. The last four Specific Aims concern the biochemical characterization of resistance genes.
Aim 4 will determine whether the Rcy1 gene product resembles the N protein by isolating and sequencing the RCY1 gene.
Aim 5 will further characterize the elicitor of the Rcy1 response, the CMV-Y coat protein.
Aim 6 will test the function of a putative nucleotide binding site found in the N protein. Binding of nucleotides and nucleotide analogs to the protein will be done to determine the specificity of the interaction. Dr. Dinesh-Kumar will determine if the N protein is an NTPase or kinase, including testing if it is phosphorylated by itself or other cytosolic proteins.
Aim 7 will determine whether N protein directly or indirectly interacts with its elicitor, TMV replicase.
| Padmanabhan, Meenu S; Ma, Shisong; Burch-Smith, Tessa M et al. (2013) Novel positive regulatory role for the SPL6 transcription factor in the N TIR-NB-LRR receptor-mediated plant innate immunity. PLoS Pathog 9:e1003235 |
| Hayward, Andrew P; Dinesh-Kumar, S P (2011) What can plant autophagy do for an innate immune response? Annu Rev Phytopathol 49:557-76 |
| Padmanabhan, Meenu S; Dinesh-Kumar, S P (2010) All hands on deck—the role of chloroplasts, endoplasmic reticulum, and the nucleus in driving plant innate immunity. Mol Plant Microbe Interact 23:1368-80 |
| Zhu, Xiaohong; Caplan, Jeffrey; Mamillapalli, Padmavathi et al. (2010) Function of endoplasmic reticulum calcium ATPase in innate immunity-mediated programmed cell death. EMBO J 29:1007-18 |
| Caplan, Jeffrey L; Zhu, Xiaohong; Mamillapalli, Padmavathi et al. (2009) Induced ER chaperones regulate a receptor-like kinase to mediate antiviral innate immune response in plants. Cell Host Microbe 6:457-69 |
| Padmanabhan, Meenu; Cournoyer, Patrick; Dinesh-Kumar, S P (2009) The leucine-rich repeat domain in plant innate immunity: a wealth of possibilities. Cell Microbiol 11:191-8 |
| Caplan, Jeffrey L; Mamillapalli, Padmavathi; Burch-Smith, Tessa M et al. (2008) Chloroplastic protein NRIP1 mediates innate immune receptor recognition of a viral effector. Cell 132:449-62 |
| Patel, Shalaka; Dinesh-Kumar, Savithramma P (2008) Arabidopsis ATG6 is required to limit the pathogen-associated cell death response. Autophagy 4:20-7 |
| Burch-Smith, Tessa M; Schiff, Michael; Caplan, Jeffrey L et al. (2007) A novel role for the TIR domain in association with pathogen-derived elicitors. PLoS Biol 5:e68 |
| Seay, Montrell; Patel, Shalaka; Dinesh-Kumar, Savithramma P (2006) Autophagy and plant innate immunity. Cell Microbiol 8:899-906 |
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