GC-TOF-MS analysis reveals salt stress-responsive primary metabolites in Casuarina glauca tissues

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)

“…Salt stress in Casuarina glauca induces a complex array of physiological and biochemical responses that collectively lead to stress tolerance [6,13]. These include photosynthetic adjustments related to the functioning of the photosynthetic machinery [4], as well as the activity of antioxidant enzymes closely related to maintenance of cell membrane integrity [21], osmotic balance [7,8], and lipid matrix remodeling [21]. In order to complement these studies, in this work we have examined the effects of increasing salt concentrations (0, 200, 400 and 600 mM NaCl) on the protein profiles of branchlets from non-nodulated (KNO 3 + ) and nodulated (NOD + ) C. glauca.…”

“…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 + ).…”

“…However, broad, interdisciplinary and integrate research to ascertain the contribution of symbiotic Frankia to the environmental plasticity of actinorhizal species has emerged only recently, mostly focusing on salt stress in Casuarinaceae, particularly in the model species Casuarina glauca Sieb. ex Spreng e.g., Santos et al, Ribeiro et al, Batista-Santos et al, Mansour et al, Ribeiro-Barros et al, Jorge et al, and Ngom et al [2][3][4][5][6][7][8][9]. C. glauca is a tropical tree widely used to prevent desertification and erosion, as well as to rehabilitate poor and degraded soils [1,10].…”

“…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.…”

“…This has been associated with a remarkably low level of tissue dehydration combined with strong osmotic adjustments, features that are essential to maintain a potential gradient of water influx and to sustain metabolic activity [15]. In fact, analysis of the primary metabolome of C. glauca branchlets [7,8] indicated that modifications in the pattern of accumulation of osmoprotectant molecules (neutral sugars, proline, and ornithine) were involved in salt stress tolerance. On the other hand, despite the reduction of net photosynthesis at salt concentrations of 400 mM NaCl and above, the photosynthetic assimilation potential was mainly kept at extraordinary high salt levels, indicating down-regulation of photosynthesis rather than severe damages [4].…”