MiR528 Plays Critical Roles in the Regulation of Arsenite Tolerance in Rice (Oryza sativa L.)

In our previous study, tens of miRNAs were established as being arsenic (As) stress responsive in rice. However, their functional role in As tolerance remains unclear. Here, we demonstrated that transgenic plants carrying the overexpressed (Ubi::MIR528) and inhibited miR528 (Ubi::MIM528) were more sensitive and tolerant to arsenite [As(III)] compared with wild-type (WT) rice. Under normal and stress conditions, miR528-5p and -3p were highly up-regulated in both the roots and leaves of Ubi::MIR528 transgenic plants, which exhibited a negative correlation with the expression of seven target genes. On the other hand, based on the expression patterns of miR528s and their potential target genes in Ubi::MIM528 transgenic plants, we inferred that LOC_Os07g38290.1 might play a critical role in the miR528-mediated As(III) tolerance. Moreover, compared with WT plants, Ubi::MIR528 plants showed excessive oxidative stress generation and remarkable amino acid content changes in the roots and leaves upon As(III) exposure. Notably, the expression profiles of diverse functional genes were clearly different between WT and transgenic plants. Thus, the observed As(III) sensitivity of Ubi::MIR528 plants was likely due to the strong alteration of antioxidant enzyme activity and amino acid profiles and the impairment of the As(III) uptake, translocation, and tolerance systems of rice.