Role of Secondary Metabolites and Prospects of Engineering Secondary Metabolite Production for Crop Improvement

Abstract

AbstractPlant secondary metabolites impart significant contributions in defense, stress tolerance, reproduction and are also involved in plant growth regulation and crop yield. They are of diverse chemical nature and biological functions, depending on their biosynthesis within a plant cell. Major classes of plant secondary metabolites that help regulate plant growth and development include—phytohormones, phenolics, terpenoids, nitrogen-containing compounds (alkaloids, non-protein amino acids and cyanogenic glycosides) and sulphur-containing compounds (glucosinolates, phytoalexin, defensin, etc.). They are synthesized in a relatively small amount within plant cells and exert their specific functions through several complex signaling pathways. Large-scale production of plant secondary metabolites is thus considered as one of the important strategies for crop improvement. Application of physical (UV-rays, gamma radiation, etc.), chemical (salicylic acid, jasmonic acid, melatonin, etc.) and biological elicitors (cyanobacteria, fungal and bacterial species), induction of polyploidy, nanotechnological approaches, epigenetic modification (gene overexpression, gene silencing, histone modification, etc.), transgenesis (homologous or heterologous transfer of one or more genes of specific secondary metabolite biosynthetic pathway), transcriptional and post-transcriptional regulation, etc., have been successfully applied in several crop plants for the increased production of desired secondary metabolites. However, most of the studies remain confined to the laboratory scale due to several constraints, viz. altered expression pattern, genetic instability, bioavailability, bioactivity, lack of desired quality and quantity of the products, etc. In this chapter, specific functions of plant secondary metabolites regulating the growth and development of crop plants have been thoroughly discussed. Moreover, the engineering strategies for large-scale production of secondary metabolites along with the challenges have also been elaborated.KeywordsCellular signalingCrop improvementGenetic engineeringMetabolic regulationNanotechnologyPlant secondary metabolites