New Insights into Plant Disease and Spore Formation from Two Key Proteins

Jenn Hoskins
25th June, 2024

New Insights into Plant Disease and Spore Formation from Two Key Proteins

Deletion of the effector genes AsCEP19 and AsCEP20 significantly impairs the virulence of Alternaria solani, resulting in substantially smaller disease lesions on both potato (a, c) and tomato (b, d) leaves compared to the wild-type strain.

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

Key Findings

  • Researchers at Hebei Agricultural University identified two effectors, AsCEP19 and AsCEP20, that contribute to the virulence of the fungus A. solani, which causes early blight in potatoes and tomatoes
  • Deleting AsCEP19 and AsCEP20 genes in A. solani led to abnormal conidial development, indicating these effectors influence fungal reproduction
  • The deletion mutants of AsCEP19 and AsCEP20 showed significantly reduced virulence on potato and tomato plants, highlighting their essential role in the fungus's pathogenicity
Alternaria solani is a significant necrotrophic pathogen responsible for causing early blight in potato and tomato plants. Researchers at Hebei Agricultural University have recently identified two specific effectors, AsCEP19 and AsCEP20, that contribute to the virulence of A. solani[1]. Understanding the role of these effectors can potentially lead to new strategies for managing early blight. In previous studies, it was established that intact salicylic acid (SA) signaling is crucial for potato defenses against A. solani[2]. This finding was surprising given that SA is typically associated with resistance to biotrophic pathogens rather than necrotrophs. Additionally, research has shown that fungal effectors play a critical role in modulating plant defenses and facilitating pathogen colonization[3][4]. The current study builds on these insights by focusing on the specific roles of AsCEP19 and AsCEP20 in A. solani. To explore the functions of AsCEP19 and AsCEP20, the researchers created deletion mutants of these genes in A. solani strain HWC168. They discovered that while the deletion of these effectors did not impact the vegetative growth of the fungus, it did result in abnormal conidial maturation. Specifically, there was an increase in the percentage of abnormal conidia produced in the mutant strains. Further investigation revealed that the regulatory gene abaA was significantly upregulated, and chsA, a positive regulator for conidiation, was significantly downregulated in the mutants. This suggests that AsCEP19 and AsCEP20 indirectly influence conidial development and maturation. Pathogenicity assays demonstrated that the deletion mutants of AsCEP19, AsCEP20, and the double mutant ΔAsCEP19 + AsCEP20 exhibited significantly reduced virulence on potato and tomato plants. This finding is crucial as it indicates that these effectors are essential for the pathogenicity of A. solani. To understand the localization of these effectors, the researchers performed localization assays using green fluorescent protein-tagged proteins in chili pepper leaves. They found that AsCEP19 specifically localizes to the chloroplasts of chili pepper epidermal cells, while AsCEP20 localizes to both chloroplasts and the plasma membrane. Weighted gene co-expression network analysis revealed that genes in the photosynthesis pathway were enriched in the module associated with AsCEP19 and AsCEP20. Many hub genes in this module were linked to chloroplast structure and photosynthesis, suggesting that chloroplasts are primary targets for these effectors. This finding aligns with previous research indicating that necrotrophic pathogens like A. solani often hijack plant cellular machinery to promote infection[4]. The study from Hebei Agricultural University significantly advances our understanding of the molecular mechanisms underlying the virulence of necrotrophic pathogens. By identifying the specific roles and localization of AsCEP19 and AsCEP20, researchers have uncovered potential targets for developing new strategies to manage early blight in potato and tomato plants. This research not only confirms the importance of fungal effectors in plant-pathogen interactions but also highlights the potential of targeting effector functions to enhance plant resistance.

BiochemPlant ScienceMycology

References

Main Study

1) Alternaria solani effectors AsCEP19 and AsCEP20 reveal novel functions in pathogenicity and conidiogenesis.

Published 24th June, 2024

https://doi.org/10.1128/spectrum.04214-23

Related Studies

2) Intact salicylic acid signalling is required for potato defence against the necrotrophic fungus Alternaria solani.

https://doi.org/10.1007/s11103-020-01019-6

3) Fungal effectors and plant susceptibility.

https://doi.org/10.1146/annurev-arplant-043014-114623

4) Plant genes hijacked by necrotrophic fungal pathogens.

https://doi.org/10.1016/j.pbi.2020.04.003


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