Jasmonic acid activates the ZmZIM13–ZmbHLH99 module to regulate <i>ZmNLP3.2</i> to mediate nitrate uptake in maize

Jasmonic acid (JA), a key phytohormone in plant defense, plays essential roles in regulating plant stress responses and growth. However, how JA signaling and nitrate signaling regulate nitrate uptake in maize (Zea mays L.) remains elusive. Here, we report that low-nitrate stress promotes JA accumulation in maize roots, and JA treatment leads to a low-nitrate phenotype. JA triggers ZmbHLH99 expression, encoding a transcription factor that binds to ZmNLP3.2 promoter and inhibits ZmNLP3.2 expression, thereby regulating nitrate uptake. In addition, the JA ZIM-domain (JAZ) transcriptional repressor ZmZIM13 interacts with ZmbHLH99 to release its inhibitory effect on the ZmNLP3.2-ZmNRT cascade and promotes ZmNLP3.2 expression. Furthermore, loss of ZmbHLH99 or overexpression of ZmZIM13 promotes plant growth and nitrate uptake, leading to higher grain yield. These findings reveal the transcriptional regulatory landscape of how JA signaling regulates nitrate uptake via the ZmZIM13-ZmbHLH99-ZmNLP3.2 module and integrates with nitrate signaling to coordinate plant growth and stress responses.