Silicon Modulates Molecular and Physiological Activities in Lsi1 Transgenic and Wild Lemont Rice Seedlings under Arsenic Stress

Arsenic is one of the most dangerous metalloids, and silicon is a helpful element supporting plants to withstand stress. In this study, three factors were considered, including rice accessions with three different lines, including Lsi1-RNAi line (LE-R), Lsi1 overexpression line (LE-OE), and their wild type (LE-WT), and silicon and arsenic treatments with two different levels. Analysis of variance in dry weight biomass, protein content, arsenic, and silicon concentration has shown a significant interaction between three factors. Further analysis showed that the silicon concentration of all rice seedlings under silicon treatments increased significantly. The LE-OE line has shown a higher ability to absorb silicon in hydroponic conditions than the wild type, and when the seedlings were exposed to arsenic, the concentration of arsenic in all lines increased significantly. Adding silicon to over-expressed rice lines with the Lsi1 gene creates better arsenic resistance than their wild type. These findings confirmed antagonism between silicon and arsenic, and seedlings exposed to arsenic showed a reduction in silicon concentration in all rice lines. RNA-seq analysis showed 106 differentially expressed genes in the LE-OE line, including 75 up-regulated genes and 31 down-regulated genes. DEGs in the LE-R line were 449 genes, including 190 up-regulated and 259 down-regulated genes. Adding treatment has changed the expression of Calcium-binding EGF domain-containing, Os10g0530500, Os05g0240200 in both LE-OE and LE-R roots. They showed that transgenic cultivars were more resistant to arsenic than wild-type, especially when silicon was added to the culture medium.