The impact of salinity on the symbiosis between Casuarina glauca Sieb. ex Spreng. and N2-fixing Frankia bacteria based on the analysis of Nitrogen and Carbon metabolism

Comparative Proteomic Analysis of Nodulated and Non-Nodulated Casuarina glauca Sieb. ex Spreng. Grown under Salinity Conditions Using Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS)

“…In short, the level of salt tolerance in vitro did not predict the level of salt tolerance in planta. Nevertheless, it is also noteworthy that the tolerance limits of the C. glauca ecotype used by Ngom et al [9] were lower than the limits of the C. glauca ecotype used in our studies [4,12,21], i.e., 200 mM vs. 600 mM NaCl. Systems biology approaches are the best way to thoroughly dissect the complex interactions within biological systems, and the pathways involved in stress adaptation, as well as to deepen our understanding of the expression patterns and functions of the response-associated genes and proteins [20,27].…”

“…As one of the first and most important stress targets is the photosynthetic machinery and photosynthetic efficiency reflects the ability of plants to cope with stress [15,16], and in order to complement previous studies [4,7,8,12,21], at this stage of our research we analysed the impact of increasing salt concentrations (200, 400 and 600 mM NaCl) on the proteome of C. glauca branchlets from nodulated plants, relying on symbiotic nitrogen fixation (NOD + ), and non-nodulated control plants, supplied with nitrate as nitrogen source (KNO 3 + ).…”

“…C. glauca is a tropical tree widely used to prevent desertification and erosion, as well as to rehabilitate poor and degraded soils [1,10]. Such capacity does not necessarily depend on the symbiosis with Frankia, although some strains may enhance stress tolerance [4][5][6]9,[11][12][13].…”

“…Recently, the mechanisms underlying salt stress tolerance in C. glauca and the contribution of symbiotic nitrogen fixation have been thoroughly analysed by our team. For that, we have examined the impact of increasing NaCl concentrations (200, 400 and 600 mM) on plant growth, mineral contents, water relations, photosynthesis-related parameters and non-structural sugars [4,12,13], membrane integrity and the control of oxidative stress [21], as well as the metabolome of nodules, roots and branchlets from nodulated and non-nodulated C. glauca plants [7,8,22]. According to Batista-Santos et al [4], the C. glauca ecotype used in these studies exhibits outstanding salt stress tolerance showing the first stress symptoms, i.e., phenotypic changes (chlorosis and necrosis of branchlets, reduction of stem diameter and biomass decrease in both KNO 3 + and NOD + groups; and swollen nodules with salt crystals at the surface in NOD + plants), and the impairment of photochemical (e.g., photosynthetic electron flow) and biochemical (e.g., activity of photosynthetic enzymes) parameters only at 600 mM NaCl.…”

“…Indeed, photosynthetic branchlets of C. glauca showed a marked increase of the activity of several anti-oxidative enzymes (e.g., superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase), helping to preserve membrane stability up to 400 mM NaCl [21]. Notably, this tolerance seems to be largely independent of the presence of an active N 2 -fixing symbiosis, as revealed by the fact that at 200 mM NaCl the Frankia strain used (Thr) was no longer able to fix nitrogen in C. glauca nodules [12]. However, a mutualistic response to salt stress is probably dependent on the genotype combination of macro-and microsymbiont.…”