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Histological, metabolomic, and transcriptomic differences in fir trees from a peri-urban forest under chronic ozone exposure
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  • Verónica Reyes-Galindo,
  • Juan P. Jaramillo-Correa,
  • Estela Sandoval-Zapotitla,
  • Svetlana Shishkova,
  • Cesar M. Flores-Ortiz,
  • Daniel Piñero,
  • Lewis Spurgin,
  • Claudia Martin,
  • Ricardo Torres-Jardón,
  • Claudio Zamora-Callejas,
  • Alicia Mastretta-Yanes
Verónica Reyes-Galindo
Universidad Nacional Autónoma de México Instituto de Ecología

Corresponding Author:[email protected]

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Juan P. Jaramillo-Correa
Institute of Ecology, Universidad Nacional Autónoma de México
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Estela Sandoval-Zapotitla
Universidad Nacional Autónoma de México Instituto de Biología
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Svetlana Shishkova
Universidad Nacional Autónoma de México Instituto de Biotecnología
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Cesar M. Flores-Ortiz
Universidad Nacional Autonoma de Mexico
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Daniel Piñero
Universidad Nacional Autónoma de México
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Lewis Spurgin
University of East Anglia
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Claudia Martin
University of East Anglia
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Ricardo Torres-Jardón
Universidad Nacional Autónoma de Mexico, Instituto de Ciencias de la Atmósfera y Cambio Climático
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Claudio Zamora-Callejas
Bienes Comunales Santa Rosa Xochiac
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Alicia Mastretta-Yanes
CONACYT Research Fellow assigned to CONABIO
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Abstract

Urbanization modifies ecosystem conditions and evolutionary processes. This includes air pollution, mostly as tropospheric ozone (O3), which contributes to the decline of urban and peri-urban forests. A notable case are fir(Abies religiosa) forests in the peripheral mountains southwest of Mexico City, which have been severely affected by O3 pollution since the 1970s. Interestingly, some young individuals exhibiting minimal O3—related damage have been observed within a zone of significant O3 exposure. Using this setting as a natural experiment, we compared asymptomatic and symptomatic individuals of similar age (≤15 years old; n = 10) using histological, metabolomic and transcriptomic approaches. Plants were sampled during days of high (170 ppb) and moderate (87 ppb) O3 concentration. Given that there have been reforestation efforts in the region, with plants from different source populations, we first confirmed that all analysed individuals clustered within the local genetic group when compared to a species-wide panel (Admixture analysis with ~1.5K SNPs). We observed thicker epidermis and more collapsed cells in the palisade parenchyma of needles from symptomatic individuals than from their asymptomatic counterparts, with differences increasing with needle age. Furthermore, symptomatic individuals exhibited lower concentrations of various terpenes (ß-pinene, ß-caryophylene oxide, α-caryophylene and ß-α-cubebene) than asymptomatic trees, as evidenced through GC-MS. Finally, transcriptomic analyses revealed differential expression for thirteen genes related to carbohydrate metabolism, plant defense, and gene regulation. Our results indicate a rapid and contrasting phenotypic response among trees, likely influenced by standing genetic variation and/or plastic mechanisms. They open the door to future evolutionary studies for understanding how O3 tolerance develops in urban environments, and how this knowledge could contribute to forest restoration.
Submitted to Ecology and Evolution
08 Apr 2024Review(s) Completed, Editorial Evaluation Pending
08 Apr 2024Editorial Decision: Accept
May 2024Published in Ecology and Evolution volume 14 issue 5. 10.1002/ece3.11343