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Will Casuarina glauca Stress Resilience Be Maintained in the Face of Climate Change?
Publication . Jorge, Tiago F.; Ramalho, José C.; Alseekh, Saleh; Pais, Isabel P.; Leitão, António E.; Rodrigues, Ana P.; Scotti-Campos, Paula; Ribeiro-Barros, Ana I.; Fernie, Alisdair R.
Actinorhizal plants have been regarded as promising species in the current climate change
context due to their high tolerance to a multitude of abiotic stresses. While combined salt-heat stress
effects have been studied in crop species, their impact on the model actinorhizal plant, Casuarina
glauca, has not yet been fully addressed. The effect of single salt (400 mM NaCl) and heat (control at
26/22 C, supra optimal temperatures at 35/22 C and 45/22 C day/night) conditions on C. glauca
branchlets was characterised at the physiological level, and stress-induced metabolite changes
were characterised by mass spectrometry-based metabolomics. C. glauca could withstand single
salt and heat conditions. However, the harshest stress condition (400 mM NaCl, 45 C) revealed
photosynthetic impairments due to mesophyll and membrane permeability limitations as well
as major stress-specific differential responses in C and N metabolism. The increased activity of
enzymatic ROS scavengers was, however, revealed to be sufficient to control the plant oxidative
status. Although C. glauca could tolerate single salt and heat stresses, their negative interaction
enhanced the effects of salt stress. Results demonstrated that C. glauca responses to combined
salt-heat stress could be explained as a sum of the responses from each single applied stress
Salt Stress Tolerance in Casuarina glauca: Insights from the Branchlets Transcriptome
Publication . Fernandes, Isabel; Paulo, Octávio S.; Marques, Isabel; Sarjkar, Indrani; Sen, Arnab; Graça, Inês; Pawlowski, Katharina; Ramalho, José C.; Ribeiro-Barros, Ana I.
Climate change and the accelerated rate of population growth are imposing a progressive
degradation of natural ecosystems worldwide. In this context, the use of pioneer trees represents a
powerful approach to reverse the situation. Among others, N2-fixing actinorhizal trees constitute
important elements of plant communities and have been successfully used in land reclamation at
a global scale. In this study, we have analyzed the transcriptome of the photosynthetic organs of
Casuarina glauca (branchlets) to unravel the molecular mechanisms underlying salt stress tolerance.
For that, C. glauca plants supplied either with chemical nitrogen (KNO3
+) or nodulated by Frankia
(NOD+) were exposed to a gradient of salt concentrations (200, 400, and 600 mM NaCl) and RNA-Seq
was performed. An average of ca. 25 million clean reads was obtained for each group of plants,
corresponding to 86,202 unigenes. The patterns of differentially expressed genes (DEGs) clearly
separate two groups: (i) control- and 200 mM NaCl-treated plants, and (ii) 400 and 600 mM NaCltreated
plants. Additionally, although the number of total transcripts was relatively high in both plant
groups, the percentage of significant DEGs was very low, ranging from 6 (200 mM NaCl/NOD+) to
314 (600 mM NaCl/KNO3
+), mostly involving down-regulation. The vast majority of up-regulated
genes was related to regulatory processes, reinforcing the hypothesis that some ecotypes of C. glauca
have a strong stress-responsive system with an extensive set of constitutive defense mechanisms,
complemented by a tight mechanism of transcriptional and post-transcriptional regulation. The
results suggest that the robustness of the stress response system in C. glauca is regulated by a limited
number of genes that tightly regulate detoxification and protein/enzyme stability, highlighting the
complexity of the molecular interactions leading to salinity tolerance in this species
Mechanisms of salt stress tolerance in Casuarina: a review of recent research
Publication . Ribeiro-Barros, Ana I.; Pawlowski, K.; Ramalho, J.C.
Salinization is a global concern whose extent is predicted to progressively increase over this century.
In this context, biosaline agriculture has been included in the set of climate-smart solutions to
support sustainable and resilient ecosystems. The Casuarinaceae family is widely known for its
intrinsic ability to thrive under saline environments. Therefore, understanding the mechanisms
underlying salt-tolerance in this family is of utmost importance for landscape integration and soil
rehabilitation. In this mini-review, we present the state of the art of Casuarina research – from gene to
ecosystem – in response to salinity, towards green growth and sustainable development. Based on
literature retrieval from 2000 to 2021, a general overview of salt-stress tolerance in the Casuarinaceae
is presented, and the extent of the contribution of root-nodule and arbuscular mycorrhizal symbioses,
as well as the related eco-physiological and molecular changes are discussed
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/AGR-FOR/4218/2012