Linking glucose signaling to nitrogen utilization by the OsHXK7-ARE4 complex in rice.

How reciprocal regulation of carbon and nitrogen metabolism works is a long-standing question. In plants, glucose and nitrate are proposed to act as signaling molecules, regulating carbon and nitrogen metabolism via largely unknown mechanisms. Here, we show that the MYB-related transcription factor ARE4 coordinates glucose signaling and nitrogen utilization in rice. ARE4 is retained in the cytosol in complexing with the glucose sensor OsHXK7. Upon sensing a glucose signal, ARE4 is released, is translocated into the nucleus, and activates the expression of a subset of high-affinity nitrate transporter genes, thereby boosting nitrate uptake and accumulation. This regulatory scheme displays a diurnal pattern in response to circadian changes of soluble sugars. The are4 mutations compromise in nitrate utilization and plant growth, whereas overexpression of ARE4 increases grain size. We propose that the OsHXK7-ARE4 complex links glucose to the transcriptional regulation of nitrogen utilization, thereby coordinating carbon and nitrogen metabolism. [Display omitted] • Rice glucose sensor OsHXK7 and transcription factor ARE4 form a complex in cytosol • Glucose induces ARE4 release from the complex and subsequent nuclear translocation • ARE4 transactivates expression of nitrate transporter genes OsNRT2s • ARE4 positively regulates nitrogen utilization Coordination of carbon-nitrogen metabolism is vital for crop productivity. Ma, Nian, Yu, et al. show that rice transcription factor ARE4 and glucose sensor OsHXK7 form a complex that is retained in cytosol. Glucose induces dissociation of the complex and nuclear localization of ARE4, thereby activating expression of nitrate transporter genes to promote nitrogen utilization. [ABSTRACT FROM AUTHOR]