Susceptibility and tolerance of rice crop to salt threat: Physiological and metabolic inspections

Salinity threat is estimated to reduce global rice production by 50%. Comprehensive analysis of the physiological and metabolite changes in rice plants from salinity stress (i.e. tolerant versus susceptible plants) is important to combat higher salinity conditions. In this study, we screened a total of 92 genotypes and selected the most salinity tolerant line (SS1-14) and most susceptible line (SS2-18) to conduct comparative physiological and metabolome inspections. We demonstrated that the tolerant line managed to maintain their water and chlorophyll content with lower incidence of sodium ion accumulation. We also examined the antioxidant activities of these lines: production of ascorbate peroxidase (APX) and catalase (CAT) were significantly higher in the sensitive line while superoxide dismutase (SOD) was higher in the tolerant line. Partial least squares discriminant analysis (PLS-DA) score plots show significantly different response for both lines after the exposure to salinity stress. In the tolerant line, there was an upregulation of non-polar metabolites and production of sucrose, GABA and acetic acid, suggesting an important role in salinity adaptation. In contrast, glutamine and putrescine were noticeably high in the susceptible rice. Coordination of different strategies in tolerant and susceptible lines show that they responded differently after exposure to salt stress. These findings can assist crop development in terms of developing tolerance mechanisms for rice crops

Antioxidant activities of tolerant (SS1-014) and susceptible (SS2-018) rice lines under control, low dose (50 mM NaCl) and high dose (150 mM NaCl) salinity stress.

<p>A) CAT leaf, B) CAT Root, C) APX leaf, D) APX root, E) SOD leaf and F) SOD Root. Asterisk (*) means significant changes between control and treated samples.</p

Physiological activities of tolerant (SS1-014) and susceptible (SS2-018) rice lines under control, low dose (50 mM NaCl) and high dose (150 mM NaCl) of salt stress condition.

<p>A) RWC in leaf, B) chlorophyll content in leaf, C) sodium ion content (Na⁺) in root (Na⁺), D) potassium ion content (K⁺) in root. Asterisk (*) means significant changes between control and treated samples.</p

Changes of metabolites under short-term period (8 h and 64 h) exposure of low and high lose dosage of salt treatment in tolerant and susceptible rice plants.

<p>Changes of metabolites under short-term period (8 h and 64 h) exposure of low and high lose dosage of salt treatment in tolerant and susceptible rice plants.</p

PLS-DA score plot of metabolic profile extracted from tolerant (SS1-014) and susceptible (SS2-018) rice lines following short-term NaCl treatment.

<p>(A) 8 h methanol extract, (B) 64 h methanol extract, (C) 8 h chloroform extract, (D) 64 h chloroform extract.</p

Fold changed bar graphs showing the relative levels of selected potential biomarkers for salinity stress obtained from aqueous extract.

<p>Asterisk (*) means significant changes between control and treated samples.</p