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IntroductionSeagrass meadows serve as an integral component of coastal ecosystems but are declining rapidly due to numerous anthropogenic stressors including climate change. Eelgrass wasting disease, caused by opportunisticLabyrinthulaspp., is an increasing concern with rising seawater temperature. To better understand the host-pathogen interaction, we paired whole organism physiological assays with dual transcriptomic analysis of the infected host and parasite. MethodsEelgrass (Zostera marina) shoots were placed in one of two temperature treatments, 11° C or 18° C, acclimated for 10 days, and exposed to a waterborne inoculation containing infectiousLabyrinthula zosterae(Lz) or sterile seawater. At two- and five-days post-exposure, pathogen load, visible disease signs, whole leaf phenolic content, and both host- and pathogen- transcriptomes were characterized. ResultsTwo days after exposure, more than 90% of plants had visible lesions andLzDNA was detectable in 100% percent of sampled plants in theLzexposed treatment. Concentrations of total phenolic compounds were lower after 5 days of combined exposure to warmer temperatures andLz, but were unaffected in other treatments. Concentrations of condensed tannins were not affected byLzor temperature, and did not change over time. Analysis of the eelgrass transcriptome revealed 540 differentially expressed genes in response toLzexposure, but not temperature.Lz-exposed plants had gene expression patterns consistent with increased defense responses through altered regulation of phytohormone biosynthesis, stress response, and immune function pathways. Analysis of the pathogen transcriptome revealed up-regulation of genes potentially involved in breakdown of host defense, chemotaxis, phagocytosis, and metabolism. DiscussionThe lack of a significant temperature signal was unexpected but suggests a more pronounced physiological response toLzinfection as compared to temperature. Pre-acclimation of eelgrass plants to the temperature treatments may have contributed to the limited physiological responses to temperature. Collectively, these data characterize a widespread physiological response to pathogen attack and demonstrate the value of paired transcriptomics to understand infections in a host-pathogen system.
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Transcriptome responses to single and combined stressors in seagrass populations from pristine and impacted sites reveal local adaptive features and core stress-response genes
In their natural habitats, seagrasses face multiple abiotic stressors, which can often occur simultaneously. However, most studies have only focused on growth and physiological responses to single stressors. Here, we examined transcriptome responses of the tropical seagrass Halophila stipulacea collected from a northern Gulf of Aqaba pristine site and an anthropogenically-impacted site, grown in a mesocosm, and exposed to ecologically-relevant, single and combined, thermal and excess nutrient stressors. Growth of plants from the impacted site was more tolerant to stress than plants from the pristine site. The combined thermal and nutrient stressor elicited greater transcriptome reprogramming than the single stressors in both populations and induced the expression of a combination-specific set of genes involved in stress responses. Furthermore, thermal stress exerted a dominant influence upon the transcriptome response to the combined stressor. Transcriptomes of plants from the impacted site displayed reduced responsiveness to stress, the presence of genes exhibiting a “stress-ready” mode of expression under all stressors, and increased resilience (recovery to control transcriptomes). We also identified core stress-response genes that could be leveraged as early indicators of stress in the field. Overall, our data suggest that environmental conditions in seagrass habitats can drive local molecular adaptation, and that the response of seagrasses to combined stressors associated with climate change and coastal anthropogenic stressors cannot be predicted from the response to single stressors.
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- Award ID(s):
- 1923589
- PAR ID:
- 10681763
- Publisher / Repository:
- Elsevier B.V.
- Date Published:
- Journal Name:
- Science of The Total Environment
- Volume:
- 987
- Issue:
- C
- ISSN:
- 0048-9697
- Page Range / eLocation ID:
- 179623
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1016/j.scitotenv.2025.179623
