Evaluation of physiological and molecular responses of two rice cultivars to arsenic toxicity

Arsenic (As) toxicity can be a hazardous threat to sustainable agriculture and human health. In order to investigate the effect of As (0, 25 and 50 µM) on growth, physiological traits and expression of As and Fe transporters in Tarom hashemi and Fajr rice cultivars, a factorial experiment based on a completely randomized design was conducted in 2020 in greenhouse conditions at Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran. As treatments included 0, 25 and 50 μM. The results showed that As stress enhanced the uptake and accumulation of As in the roots and leaves of both rice cultivars by increasing the expression of Lsi1, Lsi2 and Lsi6 genes. As toxicity downregulated the expression of genes involved in Fe translocation to the shoot, declined the Fe accumulation in the leaves and, consequently, reduced chlorophyll content in both rice cultivars. As stress induced oxidative stress by inducing the accumulation of hydrogen peroxide and reducing the ascorbic acid and glutathione content, resulting in lessened growth in both rice cultivars. However, higher activity of antioxidant enzymes in T. hashemi reduced the level of hydrogen peroxide and malondialdehyde compared to Fajr. Higher expression of Lsi1, Lsi2, Lsi6, YSL2 and FRDL1 genes in T. hashemi caused lower As uptake and higher Fe accumulation in leaves than Fajr, which can play an important role in improving T. hashemi growth under As toxicity. Our findings showed that T. hashemi showed more tolerance to As phytotoxicity than Fajr cultivar with a more effective defense system and regulation of the expression of genes involved in the uptake and translocation of As and Fe.