OsSAUR2, a small auxin-up RNA gene, is crucial for arsenic tolerance and accumulation in rice

Arsenic (As) contamination in rice poses a significant concern for food safety. Characterization of As-responsive genes is fundamental for rice safety production. However, little is known about the functional role of small auxin-up RNA (SAUR) genes in As-stress response in rice. Herein, we establish the involvement of OsSAUR2 in regulation of As tolerance and accumulation of rice plants. OsSAUR2 was predominantly expressed in leaves of rice seedlings, and whose expression was strongly induced in roots and shoots under arsenite [As(III)] stress. The OsSAUR2-overexpressed transgenic lines (OE-OsSAUR2) exhibited sensitive to, while the knockout mutants (Ossaur2) were more resistant to As(III). Compared with wild-type (WT) plants, OE-OsSAUR2 had significantly higher content of As in both roots and shoots, whereas Ossaur2 mutants accumulated greatly higher concentration of As in roots but extensively lower content of As in shoots. OsSAUR2 proteins were localized in the nucleus and cytomembrane, and interacted with the protein phosphatase OsPP2C72 on cytomembrane. Under the treatment with higher concentration of As(III), the expression level of OsPP2C72 gene was strongly up-regulated, especially at 3 h, 9 h, and 48 h in roots and 3 h and 12 h in shoots. These findings may add our understanding on the regulatory role of the OsSAUR2-OsPP2C72 module in response to As stress in rice.