Understanding the Role of Key Enzyme Components in Plant Pathogen Fusarium

Greg Howard
19th July, 2024

Understanding the Role of Key Enzyme Components in Plant Pathogen Fusarium

Deleting the succinate dehydrogenase subunits FfSdhA, FfSdhB, and FfSdhD significantly reduces the virulence of Fusarium fujikuroi, as mutants lacking these genes failed to cause the typical rice bakanae disease symptoms (a) and seedling elongation (b).

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

Key Findings

  • Researchers from Zhejiang University studied the roles of five succinate dehydrogenase (Sdh) subunits in the rice pathogen Fusarium fujikuroi
  • Deleting the FfSdhA, FfSdhB, and FfSdhD genes caused significant defects in fungal growth, spore production, and virulence
  • Deleting FfSdhA, FfSdhB, FfSdhC1, or FfSdhD made the fungus less sensitive to SDHI fungicides, indicating these subunits help the fungus resist these treatments
Rice bakanae disease, primarily caused by the fungus Fusarium fujikuroi, poses a significant threat to rice cultivation, leading to considerable losses in both yield and grain quality. Recent research conducted by Zhejiang University aimed to uncover the roles of various succinate dehydrogenase (Sdh) subunits in this pathogen and their implications for sensitivity to succinate dehydrogenase inhibitors (SDHIs)[1]. Succinate dehydrogenase is an enzyme complex found in the mitochondria of cells, playing a critical role in both the citric acid cycle and the electron transport chain, which are essential for energy production. The study focused on five Sdh subunits in Fusarium fujikuroi: FfSdhA, FfSdhB, FfSdhC1, FfSdhC2, and FfSdhD. By disrupting these genes individually and observing the resulting phenotypes, researchers sought to understand their specific functions and contributions to fungicide sensitivity. The findings revealed that deletion mutants of FfSdhA, FfSdhB, and FfSdhD exhibited significant defects in hyphal growth, conidiation (spore production), and virulence. These mutants also showed increased sensitivity to calcium chloride (CaCl2) and oxidative stress, indicating that these subunits are crucial for the normal growth and pathogenicity of Fusarium fujikuroi. Interestingly, while the deletion of FfSdhC1 also led to reduced mycelial growth and conidial production, the effects were less severe compared to the other three subunits. In terms of fungicide sensitivity, the deletion of FfSdhA, FfSdhB, FfSdhC1, or FfSdhD resulted in decreased sensitivity to all SDHIs tested. This suggests that these subunits play a role in the fungus's resistance to these fungicides. Notably, the researchers were unable to create a double mutant for FfSdhC1 and FfSdhC2, which implies that these two subunits might be essential for fungal survival. Further investigation revealed that the deletion of FfSdhC1 led to the up-regulation of FfSdhC2, suggesting a compensatory mechanism between these two subunits. These findings are particularly relevant in the context of previous studies on fungicide resistance in Fusarium species. For instance, a study on Fusarium asiaticum, another pathogen responsible for Fusarium head blight (FHB) in wheat, identified specific mutations in the Sdh subunits that confer resistance to the SDHI fungicide pydiflumetofen[2]. The current study builds on this knowledge by providing a more comprehensive understanding of the roles of different Sdh subunits in Fusarium fujikuroi, thereby offering insights into potential targets for managing fungicide resistance. Moreover, the study has implications for the broader issue of managing resistance in Fusarium species. Previous research has shown that resistance to other fungicides, such as benzimidazoles and phenamacril, can arise from specific genetic mutations[3][4]. For example, resistance to the benzimidazole fungicide carbendazim in Fusarium fujikuroi is linked to mutations in the β2-tubulin gene[3]. Similarly, resistance to phenamacril is associated with mutations in the Myosin-5 protein[4]. The current study adds another layer to this understanding by highlighting the role of Sdh subunits in SDHI resistance. In conclusion, the research conducted by Zhejiang University provides valuable insights into the biological functions of Sdh subunits in Fusarium fujikuroi and their role in fungicide sensitivity. By elucidating the mechanisms behind fungicide resistance, this study contributes to the development of more effective strategies for managing rice bakanae disease and other Fusarium-related crop diseases.

GeneticsBiochemMycology

References

Main Study

1) Functional analysis of all succinate dehydrogenase subunits in Fusarium fujikuroi

Published 18th July, 2024

https://doi.org/10.1186/s42483-024-00254-9

Related Studies

2) Resistance risk assessment for a novel succinate dehydrogenase inhibitor pydiflumetofen in Fusarium asiaticum.

https://doi.org/10.1002/ps.6053

3) Molecular mechanism of resistance of Fusarium fujikuroi to benzimidazole fungicides.

https://doi.org/10.1111/1574-6968.12504

4) Resistance mechanism of Fusarium fujikuroi to phenamacril in the field.

https://doi.org/10.1002/ps.4742


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