MicroRNA-targeted transcription factor gene RDD1 promotes nutrient ion uptake and accumulation in rice

Abstract

Fertilizers are often potential environmental pollutants, therefore increasing productivity and the efficiency of nutrient uptake to boost crop yields without the risk of environmental pollution is a desirable goal. Here, we show that the transcription factor encoding gene RDD1 plays a role in improving the uptake and accumulation of various nutrient ions in rice. RDD1 was found to be targeted by the microRNA miR166. An RDD1 transgene driven by a strong constitutive promoter exhibited a diurnally oscillating expression similar to that of the endogenous RDD1, and nucleotide substitution within the miR166 recognition site to prevent miR166-RDD1 mRNA pairing resulted in constitutive RDD1 expression. The RDD1 protein was localized to vascular tissue because miR166 repressed RDD1 expression in the mesophyll. The overexpression of RDD1 induced the expression of genes associated with the transport of several nutrients such as NH4+, Na+, SO42-, Cl-, PO43- and sucrose, and the uptake and accumulation of various nutrient ions under low-nutrient conditions. Moreover, the overexpression of RDD1 increased nitrogen responsiveness and grain productivity. Our results suggest that RDD1 can contribute to the increased grain productivity of rice via inducing the efficient uptake and accumulation of various nutrient ions. Significance Statement We showed that a transcription factor gene RDD1 is targeted by a microRNA, and induced the expression of genes associated with nutrient transport, the uptake and accumulation of various nutrient ions under low-nutrient conditions, and grain productivity. These results suggest that RDD1 has agronomically favorable characteristics for improving nutrient uptake and accumulation, and could lead to a reduction in the use of fertilizers, which persist in the soil as potential pollutants, causing environmental problems.