Plants have an immune system that resists infection, yet 10% of the world's agricultural production is lost annually to diseases caused by bacteria, fungi, and viruses. Understanding how disease resistance works may help combat this scourge.
In a new study published online this week in the open-access journal PLoS Biology, Tessa Burch-Smith, Savithramma Dinesh-Kumar, and colleagues show how one aspect of the plant immune system is defined by the gene-for-gene hypothesis: a plant Resistance (R) gene encodes a protein that specifically recognizes and protects against one pathogen or strain of a pathogen carrying a corresponding Avirulence (Avr) gene.
In tobacco and its relatives, the N resistance protein confers resistance to infection by the Tobacco mosaic virus (TMV). The authors used N, and the TMV Avirulence gene, p50, to investigate the mechanism of gene-for-gene resistance.
Contrary to current models, which propose that recognition of resistance genes occurs solely through their leucine-rich repeat domain, the authors show that association is mediated by a completely different region on N's Toll-interleukin-1 receptor homology domain, which is structurally similar to animal innate immunity molecules. These findings provide novel insights into how R proteins recognize pathogen Avr proteins and should help in long-term efforts to enhance crop yield.
Citation: Burch-Smith TM, Schiff M, Caplan JL, Tsao J, Czymmek K, et al. (2007) A novel role for the TIR domain in association with pathogen-derived elicitors. PLoS Biol 5(3): e68. doi:10.1371/journal.pbio.0050068.
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