The Multifaceted Functions of Plant Asparagine Synthetase: Regulatory Mechanisms and Functional Diversity in Growth...

Asparagine synthetase (AS) is a key enzyme in plant nitrogen metabolic network. Beyond its canonical role as a major nitrogen transport and storage molecule, asparagine also serves critical functions in plant immunity and tolerance to environmental stresses. This review systematically summarizes the characteristics of the core AS-mediated asparagine biosynthesis pathway and two other minor pathways in plants. It details the distribution of the AS gene family, protein structure, and evolutionary classification. The mechanisms governing AS expression are analyzed, revealing tissue-specific patterns and precise regulation by nitrogen availability, abiotic stresses, and exogenous hormones, mediated through an interactive network of cis-acting elements and transcription factors. Furthermore, the biological functions of AS are multifaceted: it influences plant biomass and nitrogen use efficiency by regulating nitrogen uptake, transport, and recycling during growth and development; it contributes to abiotic stress tolerance by synthesizing asparagine to maintain cellular osmotic balance and scavenge reactive oxygen species; and it indirectly enhances antibacterial and antiviral capacity by activating the SA signaling pathway and modulating programmed cell death. Current knowledge gaps remain regarding the crosstalk between AS-mediated signaling pathways, the upstream transcriptional regulatory network, and the balance between nitrogen utilization and disease resistance in crop breeding. Future research aimed at addressing these questions will provide a theoretical foundation and molecular targets for improving crop nitrogen use efficiency and breeding resistant cultivars.