Urban Air Pollution Doesn't Change Leaf Fungi but Activates Stress Genes

Greg Howard
18th May, 2024

Urban Air Pollution Doesn't Change Leaf Fungi but Activates Stress Genes

Needles of sacred fir, Abies religiosa, from the polluted study site either show visible stress symptoms like reddish tones (left) or remain healthy and asymptomatic (right).

Image adapted from: Flores-Almaraz et al. / CC BY (Source)

Key Findings

  • The study focused on sacred fir forests near Mexico City, examining the impact of ozone on fungal communities within tree needles
  • Ozone damage symptoms in tree needles did not correlate with changes in the types of fungi present
  • Certain fungi in asymptomatic needles showed increased expression of genes related to oxidative stress resistance, suggesting a protective role against ozone damage
Air pollution, particularly from tropospheric ozone, is a significant stressor on forest ecosystems. The sacred fir (Abies religiosa) forests in the peri-urban region of Mexico City are no exception. Tropospheric ozone is known to induce adverse effects in plants, affecting their physiological traits, foliar chemistry, and interactions with soil microbes[2]. A recent study by researchers at the Universidad Nacional Autónoma de México (UNAM) explored the relationship between ozone exposure and the fungal communities within the needles of these trees, using RNA-Seq metatranscriptomic data and ITS2 metabarcoding[1]. The study aimed to understand whether the variation in visible symptoms of ozone damage on the needles of individual trees correlated with changes in the fungal mycobiomes, which are the communities of fungi living symbiotically within the plant tissues. Previous research has indicated that tropospheric ozone can affect soil and plant biota, altering ecological processes and reducing tree growth over time[3]. This study, however, focused specifically on the fungal communities within the tree needles and their potential role in mitigating ozone damage. The researchers collected needle samples from sacred fir trees showing varying degrees of ozone-related symptoms. They analyzed the taxonomic composition of the fungal communities and assessed the gene expression profiles of these fungi. Surprisingly, the study found that the severity of ozone-related symptoms did not significantly correlate with changes in the taxonomic composition of the fungal mycobiomes. This suggests that the presence or absence of specific fungal species was not a primary factor in the trees' visible response to ozone exposure. However, the study did identify a set of genes that were differentially expressed in the fungal communities of asymptomatic needles. Specifically, 30 putative protein-coding genes were found to be upregulated, including eight genes previously associated with resistance to oxidative stress. This indicates that certain fungal communities might help mitigate the oxidative damage caused by ozone, potentially protecting the tree needles from severe symptoms. These findings are significant because they suggest a functional rather than a taxonomic role for fungal communities in responding to ozone stress. The presence of oxidative stress-related genes in asymptomatic needles implies that these fungi could be actively helping the trees cope with the damaging effects of ozone. This aligns with previous studies that have shown how fungal endophytes can inhabit plants without causing visible disease symptoms and can exhibit a range of interactions from mutualistic to antagonistic[4]. Moreover, the study illustrates the feasibility of using RNA-Seq data from global sequence repositories to characterize fungal communities and their gene expression profiles. This approach provides a powerful tool for understanding the complex interactions between plants and their associated microbial communities, especially in the context of environmental stressors like tropospheric ozone. In conclusion, while the taxonomic composition of fungal mycobiomes in sacred fir needles did not correlate with ozone symptom severity, the differential expression of oxidative stress-related genes highlights the potential protective role of these fungal communities. This study expands our understanding of how plants and their associated fungi respond to air pollution, offering insights that could inform conservation and management strategies for forest ecosystems under stress from increasing levels of tropospheric ozone.

EnvironmentGeneticsMycology

References

Main Study

1) Foliar mycobiome remains unaltered under urban air-pollution but differentially express stress-related genes

Published 17th May, 2024

https://doi.org/10.1007/s00248-024-02387-y

Related Studies

2) Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity.

https://doi.org/10.1126/sciadv.abc1176

3) Ozone effects on plants in natural ecosystems.

https://doi.org/10.1111/plb.12971

4) The endophytic continuum.

Journal: Mycological research, Issue: Vol 109, Issue Pt 6, Jun 2005


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