Delayed Plant Hormone Response Makes Pine Trees More Vulnerable to Disease

Greg Howard
31st July, 2024

Delayed Plant Hormone Response Makes Pine Trees More Vulnerable to Disease

Image Source: Natural Science News, 2024

Key Findings

  • In Spain, Pinus pinaster shows moderate resistance to pine pitch canker, while Pinus radiata is highly susceptible
  • Pinus pinaster activates defense-related genes and phytohormone pathways more quickly and robustly than Pinus radiata
  • Higher levels of defense-related phytohormones like salicylic acid, jasmonic acid, and ethylene were found in Pinus pinaster during infection
Fusarium circinatum is the pathogen responsible for pine pitch canker disease, a devastating condition affecting Pinus species globally and causing significant economic and ecological damage. In Spain, Pinus radiata is highly susceptible to this disease, while Pinus pinaster exhibits moderate resistance. Researchers at CSIC aimed to uncover the fundamental mechanisms underlying this differential resistance by comparing the two species using an integrative approach that combined gene expression and metabolomic phytohormone analyses at 5 and 10 days post inoculation[1]. Phytohormones, which are plant hormones, play a crucial role in plant defense mechanisms. The study's integrative approach involved analyzing the expression of genes and the levels of various phytohormones in both Pinus species during infection. By doing so, the researchers aimed to identify key differences in the molecular responses that could explain why Pinus pinaster is more resistant than Pinus radiata. This study builds on previous research that has highlighted the importance of phytohormone signaling in plant-pathogen interactions. For example, a study using dual RNA-sequencing (RNA-seq) technology found that resistant Pinus tecunumanii showed enriched gene ontologies and differentially expressed genes (DEGs) related to auxin, ethylene, jasmonate, and salicylate-mediated phytohormone signaling, whereas the susceptible Pinus patula exhibited a delayed and impaired response[2]. This indicates that effective coordination of phytohormone signaling is crucial for resistance against Fusarium circinatum. In the current study, the researchers collected samples from both Pinus radiata and Pinus pinaster at 5 and 10 days post inoculation. They performed gene expression analyses to identify DEGs and metabolomic analyses to measure levels of various phytohormones. The goal was to see how the two species responded to Fusarium circinatum infection at the molecular level. The findings revealed that Pinus pinaster had a more robust and timely activation of defense-related genes and phytohormone pathways compared to Pinus radiata. Specifically, genes involved in the biosynthesis and signaling of salicylic acid, jasmonic acid, and ethylene were more highly expressed in Pinus pinaster. These phytohormones are known to play key roles in plant defense, with salicylic acid often associated with resistance to biotrophic pathogens and jasmonic acid and ethylene linked to resistance against necrotrophic pathogens like Fusarium circinatum. Moreover, the metabolomic analyses showed that Pinus pinaster maintained higher levels of these defense-related phytohormones during the infection period. This aligns with earlier findings that indicated a correlation between effective phytohormone signaling and resistance to Fusarium circinatum[2]. The study also supports the idea that genetic diversity within Fusarium circinatum populations can influence disease outcomes. Previous research in the Basque Country of Spain found that the pathogen population was clonally propagating with low genetic diversity, which might impact the effectiveness of host resistance mechanisms[3]. Understanding the genetic makeup of both the pathogen and the host can provide insights into how resistance can be improved. In summary, the study by CSIC researchers provides valuable insights into the molecular mechanisms underlying resistance to Fusarium circinatum in Pinus species. By combining gene expression and metabolomic analyses, they demonstrated that Pinus pinaster's resistance is associated with a more effective and timely activation of phytohormone signaling pathways. These findings could inform future efforts to breed or engineer more resistant pine species, thereby mitigating the economic and ecological impact of pine pitch canker disease.

GeneticsBiochemPlant Science

References

Main Study

1) A delayed response in phytohormone signaling and production contributes to pine susceptibility to Fusarium circinatum

Published 30th July, 2024

https://doi.org/10.1186/s12870-024-05342-8

Related Studies

2) Dual RNA-Seq Analysis of the Pine-Fusarium circinatum Interaction in Resistant (Pinus tecunumanii) and Susceptible (Pinus patula) Hosts.

https://doi.org/10.3390/microorganisms7090315

3) A genetically homogenous population of Fusarium circinatum causes pitch canker of Pinus radiata in the Basque Country, Spain.

https://doi.org/10.1016/j.funbio.2010.12.014


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