Nitrate signaling and use efficiency in crops

Abstract

Nitrate (NO₃^-) is not only an essential nutrient but also an important signaling molecule for plant growth. Low nitrogen use efficiency (NUE) of crops is causing increasingly serious environmental and ecological problems. Understanding the molecular mechanisms of NO₃^- regulation in crops is crucial for NUE improvement in agriculture. During the last several years, significant progress has been made in understanding the regulation of NO₃^- signaling in crops, and some key NO₃^- signaling factors have been shown to play important roles in NO₃^- utilization. However, no detailed reviews have yet summarized these advances. Here, we focus mainly on recent advances in crop NO₃^- signaling, including short-term signaling, long-term signaling, and the impact of environmental factors. We also review the regulation of crop NUE by crucial genes involved in NO₃^- signaling. This review provides useful information for further research on NO₃^- signaling in crops and a theoretical basis for breeding new crop varieties with high NUE, which has great significance for sustainable agriculture.

Keywords: crop; nitrate regulation; nitrate signaling; nitrate-regulatory gene; nitrogen use efficiency.

Figure 1

Schematic representation of factors that regulate nitrate signaling in rice. Blue boxes indicate nitrate transporters. Brown ellipses indicate transcription factors. Blue cloud shapes indicate microRNA. Other shapes indicate other nitrate signaling regulators. Arrows indicate positive regulation, and blunted lines indicate negative regulation.

Figure 2

Schematic representation of factors that regulate nitrate signaling in maize and wheat The schematic representation of nitrate signaling regulators in maize (A) and wheat (B). Blue boxes indicate nitrate transporters. Brown ellipses indicate transcription factors. Other shapes indicate other nitrate signaling regulators. Arrows indicate positive regulation.