OsCBL1 modulates rice nitrogen use efficiency via negative regulation of OsNRT2.2 by OsCCA1

Background For cereal crop breeding, it is meaningful to improve utilization efficiency (NUE) under low nitrogen (LN) levels while maintaining crop yield. OsCBL1 -knockdown ( OsCBL1- KD) plants exhibited increased nitrogen accumulation and NUE in the field of low N level. Results OsCBL1 -knockdown ( OsCBL1- KD) in rice increased the expression of a nitrate transporter gene OsNRT2.2 . In addition, the expression of OsNRT2.2 , was suppressed by OsCCA1, a negative regulator, which could directly bind to the MYB-binding elements (EE) in the region of OsNRT2.2 promoter. The OsCCA1 expression was found to be down-regulated in OsCBL1- KD plants. At the low Nitrogen (N) level field, the OsCBL1-KD plants exhibited a substantial accumulation of content and higher NUE, and their actual biomass remained approximately as the same as that of the wild type. Conclusion These results indicated that down-regulation of OsCBL1 expression could upregulate the expression of OsNRT2.2 by suppressing the expression of OsCCA1 and then increasing the NUE of OsCBL1-KD plants under low nitrogen availability.