Silicon Mediated Alleviation of Salinity Stress Regulated by Silicon Transporter Genes (Lsi1 and Lsi2) in Indica Rice

Abstract

Silicon accumulation is known to improve tolerance of plants under both biotic and abiotic stress. Salinity stress is an inevitable crisis causing wide spread damage to rice leading to food insecurity. The influence of Si (1mM) on two rice cultivars cv. Ghanteswari (high accumulator) and cv.Badami (low accumulator) which differs in Si uptake potential under saline (10ds/m EC) and non-saline conditions were studied in nutrient culture. The Si transporter genes were isolated and characterized to determine their function in salinity tolerance. Under stress, there was an increase in Si accumulation, Na + /K + ratio, electrolyte leakage, lipid peroxidation and antioxidant activities. On addition of silicon, the K + uptake increased, membrane damage reduced and osmolytes balance improve under salinity. But, the level of resurgence was varied in both cultivars, due to their differential Si-accumulation. Molecular characterizations of Lsi1 protein revealed its involvement in the movement of ion and water and therefore prevent osmotic stress. The Lsi2 is responsible for removal of Na + , reducing salt toxicity. Silicon accumulation is responsible for maintenance of cell water status, osmotic balance and Na + ion exclusion during high salinity. The variable relative expression of Lsi2 provides a possible explanation for differential genotypic uptake of silicon.

Assessing Silicon-Mediated Growth Performances in Contrasting Rice Cultivars under Salt Stress

“…EL value reflects the extent of membrane damage and cellular integrity, while MDA represents the oxidative burst induced by salinity or any other stresses [ 38 ]. Salinity stress tends to increase cellular injury by enhancing EL [ 13 ]. Our findings demonstrated that salinity stress causes higher EL and MDA, particularly in the salt-sensitive BRRI dhan48, probably due to cellular oxidative damage.…”

“…Reports revealed that, after Si application in rice, thicker levels of casparian bands both in the exodermis and endodermis were formed, which might play partial roles in restricting Na + from entering the symplastic system or transpiration stream [ 49 , 50 ]. Si supplementation has also been reported to augment the cellular K + content in plants under salinity [ 13 ]. We found that 2 mM Si pre-treatment contributed to prevent the K + loss of shoot in both BRRI dhan48 and Binadhan-10 under salt stress conditions.…”

“…EL has significantly decreased in the Si-pre-treated contrasting cultivars un der salt-stress (Figure 2A). After supplementation with 1 and 2 mM Si, the EL in both th salt-induced BRRI dhan48 and Binadhan-10 reduced, respectively, by 13 In addition, shoot fresh and dry weights have been recorded to decrease remarkably in both BRRI dhan48 and Binadhan-10 after their salt exposure (Figure 1E,F). The addition of 1 and 2 mM of Si have non-significantly improved shoot fresh weight, respectively, by 29 and 51%, and shoot dry weight, respectively by 19 and 54% in salt-induced BRRI dhan48 compared with their Si-untreated control (Figure 1E,F).…”

“…Rice is normally an Si accumulator, and it can accumulate up to 10% Si, which is higher than the concentrations of essential macronutrients like nitrogen, phosphorus, and potassium that could be accumulated by rice [ 10 ]. Plants’ tolerance to both biotic and abiotic stress is known to improve with silicon accumulation [ 12 , 13 ]. Exogenous Si treatment has been a new environmentally acceptable technique to improve salt stress response in plants [ 14 ].…”