Temporal and spatial changes in ion homeostasis, antioxidant defense and accumulation of flavonoids and glycolipid in a halophyte Sesuvium portulacastrum (L.) L.

Abstract

Salinity is an important environmental constraint limiting plant productivity. Understanding adaptive responses of halophytes to high saline environments may offer clues to manage and improve salt stress in crop plants. We have studied physiological, biochemical and metabolic changes in a perennial, fast growing halophyte, Sesuvium portulacastrum under 0 mM (control), 150 mM (low salt, LS) and 500 mM (high salt, HS) NaCl treatments. The changes in growth, relative water content, cation, osmolyte accumulation, H2O2 and antioxidant enzyme activity (SOD, CAT and APX) were observed under different treatment conditions. A positive correlation was revealed for sodium ion accumulation with malondialdehyde (r2 = 0.77), proline (r2 = 0.88) and chlorophyll content (r2 = 0.82) under salt treatment while a negative correlation was observed with relative tissue water content (r2 = -0.73). The roots and leaves showed contrasting accumulation of potassium and sodium ions under LS treatment. Temporal and spatial study of sodium and potassium ion content indicated differential accumulation pattern in roots and leaves, and, high potassium levels in root. Higher H2O2 content was recorded in roots than leaves and the antioxidant enzyme activities also showed significant induction under salt treatment conditions. Gene expression profiling of sodium transporters, Sodium proton exchanger (NHX3), Vacuolar ATPase (vATPase) and Salt overly sensitive1 (SOS1) showed up regulation under salt stress after 6–24 hr of NaCl treatment. Metabolite changes in the salt stressed leaves showed increased accumulation of flavonoids (3,5-dihydroxy-6,4’-dimethoxy-flavone-7-O-[α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside], and3,5-dihydroxy-6,3’,4’-trimethoxy-flavone-7-O-[α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside] in both LS and HS treatments, while a glycolipid, 1-O-linolenyl-2-O-(palmitoyl)-3-O-galactopyranosyl glycerol, accumulated more in LS over HS treatments and control. The results suggest that differential spatial and temporal cation levels in roots and leaves, and accumulation of flavanoid and glycolipid could be responsible for salt adaptation of S. portulacastrum.

RNA-Seq analysis of Clerodendrum inerme (L.) roots in response to salt stress

“…The mechanisms of salt tolerance in halophytes have been gradually revealed over the past few years. The salt tolerance of a halophyte is determined by effective coordination between various physiological processes, metabolic pathways and gene networks under salt stress, including activation of antioxidant enzymes, induction and modulation of plant hormones, biosynthesis of compatible solutes and osmoprotectants, selective accumulation, exclusion of ions, and other mechanisms [15][16][17][18]. Furthermore, numerous genes that were isolated from halophytes have also been exploited by various modern biotechnological techniques to identify the genes that function in salt tolerance, including genes encoding for transcription factors [19,20], the Na + /H + antiporter gene [21,22] and genes encoding antioxidant enzymes [23,24].…”

FT-IR profiling reveals differential response of roots and leaves to salt stress in a halophyte Sesuvium portulacastrum (L.) L.

“…The peak at 2981 cm -1 was not spitted in salt treatments; only peak area was increased in LS. To confirm this Malondialdehyde accumulation pattern in Sesuvium under salt stress was checked in our previous work [ 14 ]. MDA is an indicator of oxidative stress and product of lipid peroxidation.…”

“…The surface sterilized, 5–6 cm long shoots with two nodes and two opposite leaves were grown in half strength Hoagland’s medium under hydroponic conditions. The four weeks old plants were subjected to 0 (control, No salt), 150 mM (Low salt, LS) and 500 mM (High salt, HS) treatment (based on previous work, [ 14 ]) in half strength Hoagland’s solution and losses due to evaporation was make up with the same strength salt solution. The plants were harvested after 28 days of treatment.…”

Salt Stress Triggered Changes in Osmoregulation and Antioxidants in Herbaceous Perennial Inula Plants (Asteraceae)

“…The increase in osmolytes might also be related to the the ion content status of the tissue. Nikalje et al, (2018) have also proved that both proline and TSS were positively correlated with Na increase and thus possible that pathways such as protection of integrity of membranes and/or improved stability of ion transporter proteins or channels might contribute to salt tolerance as well.…”

“…Cellular antioxidant system and its activation is crucial for sustaining redox balance which is a need for salt adaptation or tolerance response in plants (Nikalje et al, 2018). The activities of the target antioxidant enzymes (SOD, GPOX, APX and GR) induced in parallel with increasing salinity.…”