Rice microRNAs Profiling in Response to Nitrogen-Resupplied Condition

Nitrogen is a key component of crop plants growth. To increase the crop yield, the enormous amount of nitrogen source-containing fertilizer is used, which increases the total production cost and leads to environmental pollution caused by residual nitrogen source which crop doesn’t take up. For these reasons, many researchers are considering the increase of crop’s nitrogen use efficiency as a solution for reducing the amount of used nitrogen fertilizer. MicroRNA is a class of regulatory non-coding RNAs regulating the expression of target genes. Recent studies showed that the expression pool of microRNAs was changed in response to nutrient-deficient conditions. Also, other previous reports about roles of microRNAs in plants suggested that modulation of microRNA expression level in plants and crops is important in adapting to or resisting those nutrient-deficient stresses, which could affect crop yield. In this study, we aim to identify and characterize rice microRNAs, of which expression changes in response to condition of nitrogen starvation and supplement. We applied RNA-Seq technologies both in microRNAs pool and mRNAs pool, to comprehensively investigate responses of rice transcriptome.  We observed the expression of some genes involved in nitrogen assimilation was changed in a deprivation and re-supplied time-dependent manner. We also found that the expression of considerable numbers of microRNAs was dynamically changed in a nitrogen supply state-dependent manner, and especially, the expression level of some genes targeted by up- and down-regulated microRNAs was changed in a microRNA-dependent manner. Our study suggests that microRNAs may have roles in regulating the response of rice to nitrogen supply state and modulating nitrogen use efficiency.