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@PHDTHESIS{Jordine:1024166,
author = {Jordine, Angelina Maria Katharina},
othercontributors = {Fürtauer, Lisa Maria and van Dongen, Joost Thomas},
title = {{U}nraveling the resilience of ${S}alicornia~europaea$ :
physiological and molecular responses to combined
environmental stresses},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-11026},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2026; Dissertation, RWTH Aachen University, 2025},
abstract = {Plants are sessile organisms that must cope with
fluctuating and often extreme environ- mental conditions
through adaptive physiological and molecular mechanisms.
Climate change is increasing the frequency of abiotic stress
events, such as flooding (hypoxia) and salinity, which often
occur simultaneously in natural habitats. Understanding how
plants respond to combinations of stressors is crucial for
unraveling the mechanisms underlying stress tolerance. Most
previous studies have focused on stress-sensitive model
plants like Arabidopsis thaliana, which mainly reveal damage
responses, whereas naturally adapted halophytes offer
insights into survival strategies. Salicornia europaea, a
succulent halophyte of European salt marshes, exhibits high
tolerance to salinity and periodic flooding. In this study,
I used S. europaea to investigate the physiological,
molecular, and transcriptional responses to salt, hypoxia,
and simultaneous hypoxia-salt stress, to establish it as a
model for simultaneous stress studies. Plants exposed to
high salt concentrations (up to 2.5 M) or prolonged
submergence (6 weeks) confirmed the high resilience of S.
europaea under these stresses. Additionally, quantitative
polymerase chain reaction (PCR) analysis revealed that
hypoxia-responsive genes were induced under low oxygen
conditions, but not during natural tidal flooding,
suggesting efficient adaptation. Sequential exposure to salt
and hypoxia altered the expression of several
hypoxia-responsive genes, indicating potential crosstalk
between stress response path- ways and highlighting the
suitability of S. europaea as a model system for studying
adaptive mechanisms under combined stresses. To investigate
regulatory mechanisms, I focused on the group VII
ethylene-responsive transcription factors (ERFVIIs), which
are substrates of the oxygen-dependent PRT6-mediated
N-degron pathway integrating salinity and hypoxia responses
in A. thaliana. I assessed the involvement of ERFVIIs under
simultaneous stress by exposing Arabidopsis thaliana mutants
to salt and anoxia treatments. ERFVII-deficient mutants
displayed better survival compared to plants lacking only
HREs (Hypoxia responsive ERFVII), suggesting a specific role
in adaptation. Gene expression analysis via RT-qPCR revealed
differential regulation of RAPs (Related to APETALA2) and
HREs under simultaneous hypoxia-salt treatment. In
comparison, S. europaea displayed stronger activation of
ERFVIIs as well as hypoxia- and salt-related genes, pointing
to species-specific regulatory strategies. Finally,
transcriptome-wide analysis using RNA sequencing revealed
that combined hypoxia-salt stress induces complex
transcriptional reprogramming in S. europaea. Compared to
single stresses, simultaneous stress triggered about $10\%$
more differentially expressed genes (DEGs), with up to
$16\%$ of these DEGs being unique to the combined condition.
A comparative analysis of both groups was conducted, using
the proportion of synergistically and antagonistically
regulated genes as an indicator of their contribution to the
simultaneous stress response. Using this approach, processes
such as SUS-mediated sucrose degradation (Sucrose synthase)
as well as proline and GABA (Gamma-Aminobutyric Acid)
synthesis were found to be specifically regulated,
highlighting the interplay between metabolic and regulatory
pathways in plant adaptation to multiple stressors. Taken
together, this work demonstrates that S. europaea represents
a valuable model for investigating adaptive mechanisms to
simultaneous hypoxia-salt stress. It highlights the
importance of transcriptional reprogramming and
ERFVII-mediated signal transduction in the integration of
both stress responses. Overall, this study provides a solid
foundation for future research on combined hypoxia-salt
stress, by identifying a suitable model organism, delivering
first insights into the molecular connections between the
two stress factors, and presenting simultaneous stress
response pathways for further in-depth analyses.},
cin = {161510 / 160000},
ddc = {570},
cid = {$I:(DE-82)161510_20140620$ / $I:(DE-82)160000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-11026},
url = {https://publications.rwth-aachen.de/record/1024166},
}
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