Physiological responses and transcriptome analyses of upland rice following exposure to arsenite and arsenate

This study examines the molecular response of upland rice when exposed to different inorganic arsenic (iAs) species. One-week-old upland rice (Oryza sativa indica DOURADOAGULHA) seedlings were separately exposed to 100 μM arsenite [As(III)] and arsenate [As(V)] in hydroponic culture for 12 h. Genome-wide transcriptomic analysis revealed that 2983 and 1844 genes were responsive under As(III) and As(V) stresses, respectively. Therewere 915 shared genes between As(III) and As(V) treatments. Arsenic stress induced changes in complicated gene regulatory pathway of upland rice seedlings, including transcriptional regulation, hormone signaling, redox, transporters and detoxification process. In upland rice separately exposed to As(III) and As(V) for 12, 24, 48 and 72 h, qRT-PCR analysis showed that WRKY4, bHLH and AP2-EREBP associated with transcriptional regulation were significantly down-regulated, while NAC [NAM (no apical meristem), ATAF (Arabidopsis thaliana activating factor) and CUC (cup-shaped cotyledon)] transcription factor was up-regulated. The hormone signaling related gene OZG2, the redox related genes encoding Prx, GST, oxidoreductase and cytochrome P450, the transporter process related genes OsABCC9 and ZIP3 were affected under As stress. Under As(III) and As(V) treatments for 1 and 3 d, the malondialdehyde (MDA) contents in upland rice were increased, while catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and glutathione reductase (GR) contents were significantly declined. In addition, transcriptomic analysis showed that the genes encoding SOD, Prx, Grx and TrxR were mostly downregulated. In conclusion, the combination of transcriptome and physiological response may provide a deeper understanding about the molecular mechanism in the response to As in upland rice.