Genetic and Cultural Study Reveals Different Forms of Tree Disease

Greg Howard
31st July, 2024

Genetic and Cultural Study Reveals Different Forms of Tree Disease

The varying ability of Ecp32 effector proteins to trigger cell death in Nicotiana benthamiana (a) differs between orthologs from the 'verum', 'simile', and 'novus' morphotypes of Cyclaneusma minus (b), providing functional evidence that supports their classification as distinct groups.

Image adapted from: Tarallo et al. / CC BY (Source)

Key Findings

  • Researchers in New Zealand discovered a third morphotype of the fungus Cyclaneusma minus, named 'novus', in addition to the known 'verum' and 'simile' morphotypes
  • Genome sequencing confirmed the existence of the 'novus' morphotype and revealed differences in colony morphology and growth rates at various temperatures among the three morphotypes
  • Effector proteins, specifically the Ecp32 family, were found in all isolates, with variations in the number and types of these proteins among the different morphotypes, influencing their pathogenicity
Cyclaneusma needle cast, a disease caused by the fungus Cyclaneusma minus, significantly impacts Pinus species globally. Recent research by Massey University[1] has identified a third morphotype of C. minus in New Zealand, named 'novus', alongside the previously known 'verum' and 'simile' morphotypes. This discovery could lead to improved disease management strategies for pine trees. The study involved genome sequencing of eight C. minus isolates, which confirmed the existence of the 'novus' morphotype. Traditional mycological methods had already suggested the presence of two distinct morphotypes, but the discovery of 'novus' highlights the complexity of this pathogen. The research also identified differences in colony morphology and growth rates at various temperatures among the three morphotypes. Effector proteins, which are molecules used by pathogens to facilitate infection, were a focal point of this study. Specifically, the researchers analyzed the Ecp32 family of effector proteins, known to induce cell death in host plants. These proteins were found to be present in all eight isolates, with variations in the number of Ecp32 family members among the different morphotypes. Some members of this protein family were unique to either the 'simile' or 'verum' morphotypes, and patterns of pseudogenization (loss of gene function) were observed in the 'simile' morphotype. Interestingly, the Ecp32 proteins triggered cell death in non-host Nicotiana species, indicating their potential role in the pathogenicity of C. minus. Structural analysis revealed that these proteins adopt a β-trefoil fold, a common structure in effector proteins of other plant pathogens. This finding aligns with previous research on fungal effector proteins, which have been shown to facilitate host-plant colonization by inducing cell death[2]. The identification of three distinct morphotypes of C. minus has significant implications for understanding and managing pine needle diseases. By recognizing these morphotypes as potentially distinct species, researchers can better understand their geographical distribution, virulence, and pathogenicity. This knowledge is crucial for developing durable disease control methods. Previous studies have highlighted the importance of breeding for disease resistance in Pinus radiata, a common pine species in New Zealand. For example, research has shown moderate heritability of resistance to various needle diseases, suggesting that breeding programs could effectively enhance resistance[3]. The current study's findings on the diversity of C. minus morphotypes could inform such breeding programs, enabling more targeted selection of resistant genotypes. Moreover, the study's focus on effector proteins ties into broader research on plant-pathogen interactions. The zigzag model of plant immunity describes how plants detect and respond to pathogen-associated molecular patterns (PAMPs) and effectors[4]. Understanding the specific effectors involved in C. minus pathogenicity, like the Ecp32 family, can provide insights into how pine trees recognize and respond to this pathogen. In conclusion, the discovery of a third morphotype of Cyclaneusma minus by Massey University adds a new layer of complexity to our understanding of pine needle diseases. By identifying and characterizing effector proteins, researchers have provided valuable insights into the pathogenic mechanisms of this fungus. This knowledge will be instrumental in developing more effective disease management strategies and breeding programs for resistant pine trees.

GeneticsBiochemPlant Science

References

Main Study

1) Genomic and culture-based analysis of Cyclaneusma minus in New Zealand provides evidence for multiple morphotypes

Published 30th July, 2024

https://doi.org/10.1186/s42483-024-00255-8

Related Studies

2) Conservation and expansion of a necrosis-inducing small secreted protein family from host-variable phytopathogens of the Sclerotiniaceae.

https://doi.org/10.1111/mpp.12913

3) Indication of Quantitative Multiple Disease Resistance to Foliar Pathogens in Pinus radiata D.Don in New Zealand.

https://doi.org/10.3389/fpls.2020.01044

4) Understanding plant immunity as a surveillance system to detect invasion.

https://doi.org/10.1146/annurev-phyto-080614-120114


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