Silicon induces adventitious root formation in rice under arsenate stress with involvement of nitric oxide and indole-3-acetic acid

Arsenic (As) negatively affects plant development. This study evaluates how the application of silicon (Si) can favor the formation of adventitious roots in rice under arsenate stress (As-V) as a mechanism to mitigate its negative effects. The simultaneous application of As-V and Si up-regulated the expression of genes involved in nitric oxide (NO) metabolism, cell cycle progression, auxin (IAA, indole-3-acetic acid) biosynthesis and transport, and Si uptake which accompanied adventitious root formation. Furthermore, Si triggered the expression and activity of enzymes involved in ascorbate recycling. Treatment with L-NAME (N-G-nitro L-arginine methyl ester), an inhibitor of NO generation, significantly suppressed adventitious root formation, even in the presence of Si; however, supplying NO in the growth media rescued its effects. Our data suggest that both NO and IAA are essential for Si-mediated adventitious root formation under As-V stress. Interestingly, TIBA (2,3,5-triiodobenzoic acid), a polar auxin transport inhibitor, suppressed adventitious root formation even in the presence of Si and SNP (sodium nitroprusside, an NO donor), suggesting that Si is involved in a mechanism whereby a cellular signal is triggered and that first requires NO formation, followed by IAA biosynthesis.