Shin-Mei Yeh, Minsoo Yoon, Sidney Scott, Abhishek Chatterjee, Lauren M. Hemara, Ronan K. Y. Chen, Tianchi Wang, Kerry Templeton, Erik H. A. Rikkerink, Jay Jayaraman, Cyril Brendolise

Plant, Cell & Environment; First published: 20 June 2024; https://doi.org/10.1111/pce.15002

Abstract

Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) causes a devastating canker disease in yellow-fleshed kiwifruit (Actinidia chinensis). The effector HopZ5, which is present in all isolates of Psa3 causing global outbreaks of pandemic kiwifruit canker disease, triggers immunity in Nicotiana benthamiana and is not recognised in susceptible A. chinensis cultivars. In a search for N. benthamiana nonhost resistance genes against HopZ5, we found that the nucleotide-binding leucine-rich repeat receptor NbPTR1 recognised HopZ5. RPM1-interacting protein 4 orthologues from N. benthamiana and A. chinensis formed a complex with NbPTR1 and HopZ5 activity was able to disrupt this interaction. No functional orthologues of NbPTR1 were found in A. chinensis. NbPTR1 transformed into Psa3-susceptible A. chinensis var. chinensis ‘Hort16A’ plants introduced HopZ5-specific resistance against Psa3. Altogether, this study suggested that expressing NbPTR1 in Psa3-susceptible kiwifruit is a viable approach to acquiring resistance to Psa3 and it provides valuable information for engineering resistance in otherwise susceptible kiwifruit genotypes.

See https://onlinelibrary.wiley.com/doi/10.1111/pce.15002

Figure 1

NbPTR1a mediates a HopZ5-triggered immune response in Nicotiana benthamiana. (a, b) HopZ5-triggered hypersensitive response (HR) is reduced by hp#1 and the m1 fragment. N. benthamiana leaves were agroinfiltrated with pTKO2_GGT control vector (CV), hp#1, or one of six DNA target fragments in hp#1: m1, m2, u10, u120, u147 and u156, each at OD₆₀₀ of 0.2, followed by agroinfiltration of HopZ5 (OD₆₀₀ of 0.05) 48 h later. Leaves were photographed 6 days postinoculation (dpi). Red dash line indicated the HopZ5-inoculated area. (c) Schematic of PTR1 gene structure in N. benthamiana (NbPTR1a and NbPTR1b). The coiled-coil (CC), nucleotide binding site present in APAF-1, R proteins and CED-4 (NB-ARC), and leucine-rich repeat (LRR) domains are indicated in grey rectangles. The black bar indicates the area targeted by m1, corresponding to position 1291–1441 bp relative to NbPTR1a. NbPTR1b has a 5-bp deletion (grey bar) at position 97 bp resulting in a premature stop codon (asterisk) at position 159 bp. (d) Transient complementation of NbPTR1_syn. N. benthamiana leaves were agroinfiltrated with m1 + NbPTR1_syn, m1 + GUS, CV + NbPTR1_syn or CV + GUS, each at OD₆₀₀ of 0.1, followed by agroinfiltration with HopZ5 or GUS control (each at OD₆₀₀ of 0.2) 48 h later. Leaves were photographed 4 dpi. (e) Quantification of the HR by electrolyte leakage. Conductivity was measured from leaf disks collected at 2 day postfinal infiltration from the leaf patches shown in (d). Error bars represent the standard errors of the means for 10 independent biological replicates, collected from two independent experimental runs (n = 10). HopZ5 was used as positive control and infiltration buffer (10 mM MgCl₂, 100 μM acetosyringone) as a negative control. Letters indicate statistically significant differences from a one-way analysis of variance and Tukey's HSD post hoc test for values at 26 h postsampling. [Color figure can be viewed at wileyonlinelibrary.com]