NRT1.1B acts as an abscisic acid receptor in integrating compound environmental cues for plants

Abstract

Abscisic acid (ABA) is the most crucial phytohormone for plants in adapting to environmental conditions. While the ABA signaling network in plants has been extensively explored, our understanding of the diverse ABA sensing systems remains limited. Here, we found that the transcriptional response to ABA is suppressed under high-nitrate conditions but substantially increases under low-nitrate conditions, suggesting a tight integration of ABA signaling with nutrient conditions. Interestingly, NRT1.1B, traditionally recognized as a nitrate transporter and receptor, exhibits a markedly higher affinity for ABA, leading to the formation of an ABA-facilitated NRT1.1B-SPX4 complex. This complex triggers the release of SPX4-sequestered transcription factor NLP4, thereby initiating the transcriptional response to ABA. These findings establish that NRT1.1B functions as an ABA receptor. Notably, the competitive binding of nitrate and ABA to NRT1.1B unveils a mechanism that enables a flexible ABA response to fluctuating nutrient conditions, illustrating a sophisticated strategy for integrating compound environmental cues.

Keywords: NRT1.1B; abscisic acid; integration; nitrate; receptor; signal perception.