Sucrose plays key role in amelioration of arsenic induced phytotoxicity through modulating phosphate and silicon transporters, physiological and biochemical responses in C3 (Oryza sativa L.) and C4 (Zea mays L.)

Sucrose is a precursor for several vital biomolecules and essential for growth of the plant. The present study investigated the interrelationship between sucrose (25 mu M) and PO4 (iP) in amelioration of arsenic (iAs) [60 mu M of AsIII and AsV] toxicity in C-3 (Oryza sativa) and C-4 (Zea mays) plants. Application of sucrose recovered the iAs induced phytotoxicity, morphological and physiological parameters in both C-3 and C-4 plant seedlings. Alternatively, iAs accumulation enhanced the endogenous level of sucrose in the seedlings. Also, sucrose suppressed the gene expression of low silicon transporters in both C-3 and C-4 plants, resulting in lower iAs uptake. Presence of iP, suppressed expression of root iP transporters which coincided with reduced iAs accumulation in maize root (23 %) over its AsIII, and that in shoots of both of C-3 (12 %) and C-4 (35 %) seedlings over AsV. However, the iP transporters in rice [OsPT-1, 6 & 9] and in maize (ZmPHT1;6, ZmPHT2;1, ZmPHT1;1), shoot and root, respectively, were upregulated with sucrose application, enhancing the iP accumulation. Sucrose application reduced the level of H2O2 and TSARS in both plants, while enhanced the thiolic compounds (GSH, cysteine and NPSH) and activities of antioxidant enzymes (APX, GPX and SOD) against iAs toxicity under both available and iP deprived conditions. The physiological parameters such as A, PhiPS2, gs and qP recovered whereas, NPQ was reduced with sucrose application, towards iAs treatments in both the seedlings. Overall, the results indicate that sucrose plays a vital role in the amelioration of iAs induced toxicity through modulation of iP and low silicon transporters, resulting in reducing the iAs accumulation, physiological parameters and antioxidants.