Transcriptomic changes and signalling pathways induced by arsenic stress in rice roots.

Arsenic (As) is considered the most common toxic metalloid, but its molecular mode of action is not well understood. We investigated whether arsenate [As(V)] can induce intracellular reactive oxygen species production and calcium oscillation in rice roots. To better understand the molecular basis of plant cell responses to As, we performed a large-scale analysis of the rice transcriptome during As(V) stress. As(V) induced genes involved in abiotic stress, detoxification pathways and secondary metabolic process. Genes involved in secondary cell wall biogenesis, cell cycle and oligopeptide transport were mainly downregulated. Genes encoding signalling components such as receptor-like cytoplasmic kinases protein kinase, APETALA2/ethylene response factor, heat shock factor, MYB and zinc-finger protein expressed in inflorescence meristem transcription factors were increased in expression. The expression of GARP-G2-like and C3H transcription factors was specifically modulated by As(V) stress. The predominant families of As(V)-regulated transporters belonged to the ATP-binding cassette superfamily and telurite-resistance/dicarboxylate transporters. Several factors involved in signaling, such as mitogen-activated protein kinase (MAPK), MAPK kinase kinase and calcium-dependent protein kinase (CDPK), were also upregulated. Moreover, As(V) markedly increased the activity of MAPKs and CDPK-like kinases, and CDPK and NADPH oxidases were involved in As-induced MAPK activation. Further characterization of these As(V)-responsive genes and signalling pathways may help better understand the mechanisms of metalloid uptake, tolerance and detoxification in plants.