Artemis Giannakopoulou | bioRxiv Science

bioRxiv2016

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

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.

Plant Biology↗

bioRxiv2015

Tomato I2 immune receptor can be engineered to confer partial resistance to the oomycete Phytophthora infestans in addition to the fungus Fusarium oxysporum

Plants and animals rely on immune receptors, known as nucleotide-binding domain and leucine-rich repeat containing proteins (NB-LRR or NLR), to defend against invading pathogens and activate immune responses. How NLR receptors respond to pathogens is inadequately understood. We previously reported single-residue mutations that expand the response of the potato immune receptor R3a to AVR3aEM, a stealthy effector from the late blight oomycete pathogen Phytophthora infestans. I2, another NLR that mediates resistance to the wilt causing fungus Fusarium oxysporum f. sp. lycopersici, is the tomato ortholog of R3a. We transferred previously identified R3a mutations to I2 to assess the degree to which the resulting I2 mutants have an altered response. We discovered that wild-type I2 protein responds weakly to AVR3a. One mutant in the N-terminal coiled-coil domain, I2I141N, appeared sensitized and displayed markedly increased response to AVR3a. Remarkably, I2I141N conferred partial resistance to P. infestans. Further, I2I141N has an expanded response spectrum to F. oxysporum f. sp. lycopersici effectors compared to the wild-type I2 protein. Our results suggest that synthetic immune receptors can be engineered to confer resistance to phylogenetically divergent pathogens and indicate that knowledge gathered for one NLR could be exploited to improve NLRs from other plant species.

Plant Biology↗