Effects of anoxic and aerobic cultivation conditions on cadmium accumulation and OsHMA2 expression in rice

Objective  To study the effects of anoxic and aerobic cultivation conditions on cadmium (Cd) uptake and transfer and OsHMA2 expression in rice shoots, and provide a theoretical basis for reducing the uptake and accumulation of heavy metals in rice.

Method  Using rice cultivar ‘Wufengyou 2168’, pot experiments were performed hydroponically under anoxic(nutrient solution with agar) and aerobic(oxygenized nutrient solution) conditions. Cd uptake and accumulation, and OsHMA2 expression levels in rice shoots were analyzed at three Cd levels(0, 0.6, 1.2 mg·L^–1).

Result  Rice growth was not significantly inhibited by Cd under anoxic condition, but was significantly inhibited under aerobic condition with the dry weight of roots and above ground parts significantly decreased. At the Cd concentration of 0.6 and 1.2 mg·L^–1, Cd accumulations in roots and above ground parts of rice under anoxic condition were lower than those under aerobic condition. Under both anoxic and aerobic conditions, Cd accumulation in roots increased with Cd concentration. For above ground parts of rice, Cd accumulation was not significantly different between 0.6 and 1.2 mg·L^–1 Cd levels under anoxic condition, but increased with Cd concentration under aerobic condition. Compared with the control (0 mg·L^–1 Cd), OsHMA2 expression level increased at the Cd concentration of 0.6 mg·L^–1 but decreased at 1.2 mg·L^–1 in shoots under both anoxic and aerobic condition, and OsHMA2 expression level in rice was higher under anoxic condition than those aerobic condition at each Cd level.

Conclusion  Anoxic culture can inhibit Cd uptake and accumulation in rice, and OsHMA2 expression decreases when Cd accumulation reaches a certain value.