Emerging roles of NAC transcription factor in medicinal plants: progress and prospects.

Transcriptional factors act as mediators in regulating stress response in plants from signal perception to processing the directed gene expression. WRKY, MYB, AP2/ERF, etc. are some of the major families of transcription factors known to mediate stress mechanisms in plants by regulating the production of secondary metabolites. NAC domain-containing proteins are among these large transcription factors families in plants. These proteins play impulsive roles in plant growth, development, and various abiotic as well as biotic stresses. They are involved in regulating the different signaling pathways of plant hormones that direct a plant's immunity against pathogens, thereby affecting their immune responses. However, their role in stress regulation or defence mechanism in plants through the secondary metabolite biosynthesis pathway is studied for very few cases. Emerging concern over the requirement of medicinal plants for the production of biocompatible drugs and antibiotics, the study of these vast, affecting proteins should be focused to improve their qualitative and quantitative production further. In medicinal plants, phytochemicals and secondary metabolites are the major biochemicals that impose antimicrobial and other medicinal properties in these plants. This review compiles the NAC transcription factors reported in selected medicinal plants and their possible roles in different mechanisms. Further, the comprehensive understanding of the molecular mechanism, genetic engineering, and regulation responses of NAC TFs in medicinal plants, can lead to improvement in stress response, immunity, and production of usable secondary metabolites.