The potato NLR immune receptor R3a does not contain non-canonical integrated domains

Abstract

A recent study by Kroj et al. (New Phytologist, 2016) surveyed nucleotide binding-leucine rich repeat (NLR) proteins from plant genomes for the presence of extraneous integrated domains that may serve as decoys or sensors for pathogen effectors. They reported that a FAM75 domain of unknown function occurs near the C-terminus of the potato late blight NLR protein R3a. Here, we investigated in detail the domain architecture of the R3a protein, its potato paralog R3b, and their tomato ortholog I2. We conclude that the R3a, R3b, and I2 proteins do not carry additional domains besides the classic NLR modules, and that the FAM75 domain match is likely a false positive among computationally predicted NLR-integrated domains.