Gene NbPTR1 Helps Kiwifruit Resist Harmful Bacteria

Jenn Hoskins
21st June, 2024

Gene NbPTR1 Helps Kiwifruit Resist Harmful Bacteria

Transferring the immune gene NbPTR1 from the model plant Nicotiana benthamiana into susceptible kiwifruit (Actinidia chinensis, pictured) provides effective resistance against the bacterial pathogen that causes canker disease.

Photo adapted from: Katja Schulz / CC BY (Source)

Key Findings

  • Researchers at The New Zealand Institute for Plant & Food Research Limited found that the immune receptor NbPTR1 in Nicotiana benthamiana recognizes the HopZ5 effector from the Psa3 pathogen
  • The study revealed that susceptible kiwifruit cultivars lack functional orthologues of NbPTR1, explaining their vulnerability to Psa3
  • Transforming susceptible kiwifruit plants with NbPTR1 conferred resistance to Psa3, suggesting a potential method for engineering disease-resistant kiwifruit
Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) is a bacterial pathogen that causes a severe canker disease in yellow-fleshed kiwifruit (Actinidia chinensis), leading to significant agricultural losses. The pathogen's effector protein, HopZ5, is present in all Psa3 isolates responsible for global outbreaks of this disease. Interestingly, while HopZ5 triggers immune responses in Nicotiana benthamiana, a model plant species, it is not recognized by susceptible A. chinensis cultivars. This differential recognition prompted researchers at The New Zealand Institute for Plant & Food Research Limited (PFR) to investigate the underlying mechanisms and explore potential avenues for engineering resistance in kiwifruit[1]. The study discovered that the nucleotide-binding leucine-rich repeat receptor (NLR) NbPTR1 in N. benthamiana recognizes the HopZ5 effector. NLRs are a class of immune receptors in plants that detect pathogen effectors and initiate immune responses. The researchers found that RPM1-interacting protein 4 (RIN4) orthologues from both N. benthamiana and A. chinensis form a complex with NbPTR1. However, the presence of HopZ5 disrupts this interaction, suggesting a mechanism by which the effector undermines plant immunity. Interestingly, no functional orthologues of NbPTR1 were found in A. chinensis, explaining the susceptibility of certain kiwifruit cultivars to Psa3. To test whether introducing NbPTR1 could confer resistance, the researchers transformed Psa3-susceptible A. chinensis var. chinensis 'Hort16A' plants with NbPTR1. Remarkably, this transformation introduced HopZ5-specific resistance against Psa3, indicating that NbPTR1 is a viable candidate for engineering disease resistance in kiwifruit. This finding builds on previous research showing the role of NLRs in plant immunity. For instance, NLRs in Arabidopsis thaliana, such as RPM1 and RPS2, are known to activate immune responses upon detecting pathogen effectors that target the host protein RIN4[2]. The study on N. benthamiana aligns with this, as NbPTR1 also interacts with a RIN4 orthologue to recognize HopZ5, highlighting a conserved mechanism of effector recognition across different plant species. Moreover, the study contributes to the broader understanding of NLR diversity and function. NLRs are highly diversified both within and between species, which complicates the prediction of their roles in disease resistance[3]. By identifying NbPTR1 as a key player in recognizing HopZ5, the research provides a valuable addition to the growing pan-NLRome, aiding future efforts to predict NLR functions from sequence data alone. The study also underscores the importance of type III effectors, which are proteins injected by phytopathogenic bacteria into plant cells to suppress innate immunity[4]. HopZ5, like other type III effectors, manipulates host cellular processes to promote bacterial pathogenesis. Understanding how plants recognize and respond to such effectors is crucial for developing resistant crop varieties. Nicotiana benthamiana's well-characterized susceptibility to diverse pathogens and its amenability to genetic manipulation make it an ideal model for studying plant-microbe interactions[5]. The availability of its genome sequence has facilitated the identification of key immune components, such as NbPTR1, and their orthologues in other species. This comparative approach is essential for translating findings from model plants to economically important crops like kiwifruit. In summary, the study by PFR demonstrates that expressing NbPTR1 in susceptible kiwifruit cultivars can confer resistance to the devastating Psa3 pathogen. This research not only provides a practical solution for protecting kiwifruit but also enhances our understanding of plant immunity and the role of NLRs in recognizing pathogen effectors. The findings pave the way for future efforts to engineer disease-resistant crops, leveraging the natural diversity and specificity of plant immune receptors.

FruitsGeneticsPlant Science

References

Main Study

1) NbPTR1 confers resistance against Pseudomonas syringae pv. actinidiae in kiwifruit.

Published 20th June, 2024

https://doi.org/10.1111/pce.15002

Related Studies

2) Ptr1 and ZAR1 immune receptors confer overlapping and distinct bacterial pathogen effector specificities.

https://doi.org/10.1111/nph.19073

3) Plant NLR diversity: the known unknowns of pan-NLRomes.

https://doi.org/10.1093/plcell/koaa002

4) Phytopathogen type III effector weaponry and their plant targets.

https://doi.org/10.1016/j.pbi.2008.06.007

5) A draft genome sequence of Nicotiana benthamiana to enhance molecular plant-microbe biology research.

https://doi.org/10.1094/MPMI-06-12-0148-TA


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