Tomato Prf requires NLR helpers NRC2 and NRC3 to confer resistance against the bacterial speck pathogen Pseudomonas syringae pv. tomato
Bacterial speck, caused by the pathogen Pseudomonas syringae pv. tomato, is one of the most common diseases in tomato (Solanum lycopersicum) production. Together with Pto kinase, the NLR (nucleotide-binding domain leucine-rich repeat containing) protein Prf confers resistance against the bacterial speck pathogen by recognizing AvrPto and AvrPtoB, two Type III effector proteins secreted by P. syringae pv. tomato. This Prf/Pto pathway is part of a complex NLR network in solanaceous plants that mediates resistance to diverse pathogens through the helper NLR proteins NRCs (NLR required for cell death). We previously showed that in Nicotiana benthamiana the hypersensitive cell death elicited by expression of AvrPto and Pto, which activate immunity through the endogenous Prf ortholog NbPrf, requires functionally redundant NRC2 and NRC3. However, whether tomato Prf (SlPrf) confers resistance to the bacterial speck pathogen through NRC2 and NRC3 has not been determined. In this study, we show that SlPrf requires NRC2 and NRC3 to trigger hypersensitive cell death and disease resistance in both N. benthamiana and tomato. We found that the hypersensitive cell death induced by AvrPtoB/Pto/SlPrf in N. benthamiana is compromised when NRC2 and NRC3 are silenced, indicating that SlPrf is an NRC2/3-dependent NLR. We validated this finding by showing that silencing NRC2 and NRC3 in the bacterial speck resistant tomato LSQUORio Grande 76RRSQUO compromised Prf-mediated resistance. These results indicate that the NRC network extends beyond N. benthamiana to solanaceous crops.
Wu, C.H. and Kamoun, S. (2021). Tomato Prf requires NLR helpers NRC2 and NRC3 to confer resistance against the bacterial speck pathogen Pseudomonas syringae pv. tomato. Acta Hortic. 1316, 61-66
Pseudomonas syringae, plant immunity, NLR network, disease resistance, NLR required for cell death