Nonsense-mediated mRNA decay (NMD) is a conserved eukaryotic RNA surveillance mechanism that degrades aberrant mRNAs. NMD impairment in Arabidopsis is linked to constitutive immune response activation and enhanced antibacterial resistance, but the underlying mechanisms are unknown. Here we show that NMD contributes to innate immunity in Arabidopsis by controlling the turnover of numerous TIR domain-containing, nucleotide-binding, leucine-rich repeat (TNL) immune receptor-encoding mRNAs. Autoimmunity resulting from NMD impairment depends on TNL signaling pathway components and can be triggered through deregulation of a single TNL gene, RPS6. Bacterial infection of plants causes host-programmed inhibition of NMD, leading to stabilization of NMD-regulated TNL transcripts. Conversely, constitutive NMD activity prevents TNL stabilization and impairs plant defense, demonstrating that host-regulated NMD contributes to disease resistance. Thus, NMD shapes plant innate immunity by controlling the threshold for activation of TNL resistance pathways.

Department of Plant Breeding and Genetics Max Planck Institute for Plant Breeding Research Carl von Linné Weg 10 50829 Cologne Germany

Department of Plant Breeding and Genetics Max Planck Institute for Plant Breeding Research Carl von Linné Weg 10 50829 Cologne Germany; Institut Jean Pierre Bourgin UMR1318 INRA AgroParisTech 78000 Versailles France

Department of Plant Microbe Interactions Max Planck Institute for Plant Breeding Research Carl von Linné Weg 10 50829 Cologne Germany

Gregor Mendel Institute Austrian Academy of Sciences Vienna Biocenter Dr Bohr Gasse 3 1030 Vienna Austria

Gregor Mendel Institute Austrian Academy of Sciences Vienna Biocenter Dr Bohr Gasse 3 1030 Vienna Austria; CEITEC Masaryk University Kamenice 753 5 625 00 Brno Czech Republic

Cell Host Microbe. 2014 Sep 10;16(3):273-5. doi: 10.1016/j.chom.2014.08.015. PubMed

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