Abstract

For innate immunity, seed plant species have evolved large families of variable receptors to detect pathogen molecules and trigger disease resistance. Intracellular nucleotide-binding/leucine-rich-repeat (NLR) receptors are major determinants of resistance against host-adapted pathogens. Recent advances have been made in determining biochemical processes underlying NLR activation by different pathogen molecules and how pathogen-specific recognition events then signal to resistance and cell death execution machineries. My group has been studying a large NLR receptor sub-class in dicot plants called TIR -NLRs (TNLs) which have Toll-Interleukin1-receptor (TIR) enzymatic signalling domains. I’ll describe our current understanding of TIR domain catalytic functions, when embedded in NLRs but also as TIR -only (non-NLR) proteins, in generating nucleotide-based second messengers for immunity. I’ll also consider emerging evidence of TIR catalytic versatility in producing nucleotide-based stimulators and suppressors of host immune responses across kingdoms.