Contemporary Understanding of miRNA-Based Regulation of Secondary Metabolites Biosynthesis in Plants

Abstract

Plant's secondary metabolites such as flavonoids, terpenoids, and alkaloids etc. are known for their role in the defense against various insects-pests of plants and for medicinal benefits in human. Due to the immense biological importance of these phytochemicals, understanding the regulation of their biosynthetic pathway is crucial. In the recent past, advancement in the molecular technologies has enabled us to better understand the proteins, enzymes, genes, etc. involved in the biosynthetic pathway of the secondary metabolites. miRNAs are magical, tiny, non-coding ribonucleotides that function as critical regulators of gene expression in eukaryotes. Despite the accumulated knowledge of the miRNA-mediated regulation of several processes, the involvement of miRNAs in regulating secondary plant product biosynthesis is still poorly understood. Here, we summarize the recent progress made in the area of identification and characterizations of miRNAs involved in regulating the biosynthesis of secondary metabolites in plants and discuss the future perspectives for designing the viable strategies for their targeted manipulation.

Identification, characterization and expression analysis of passion fruit (Passiflora edulis) microRNAs

“…In plant, mature miRNAs are generated from the long stem-loop primary transcript (pre-miRNA) by a dicer-like RNA endonuclease via the intermediate step of pre-miRNA synthesis, and finally the RNA inducing silencing complex (RISC) guided by ARGONAUTE 1 (AGO1) protein directs the miRNA to the complementary target mRNA sequence (Voinnet 2009). Plant microRNAs are reported to possess important functions in several metabolic and biological pathways such as tissue development and differentiation, biotic and abiotic stress responses, phytohormones signaling, and secondary metabolite production (Wu 2013;Rajwanshi et al 2014;Paul et al 2011Paul et al , 2017Paul et al , 2018Sharma et al 2019;Gupta et al 2017). Nonetheless, the evolutionary highly conserved nature of an extensive number of miRNAs simplified the process of characterization of novel miRNA orthologs in new plant species through homologs identification (Zhang et al 2006b;Ye et al 2013;Sharma et al 2019).…”

MicroRNAs Associated with Secondary Metabolites Production

“…of phytochemicals that regulate various processes related to the interaction of the plant with its environment [19]. These compounds include terpenoids, alkaloids, phenolics, glycosides, tannins, and saponins, and defend plants from several biotic an abiotic stressors [20]. Even though these types of compounds are synthesized by plants to help in self-defense, they have diverse industrial uses such as insecticides, dyes, flavoring compounds, and nutraceuticals having a positive effect on human health.…”

“…It is known that miRNAs control several biological processes at the posttranscriptional level. Currently, some studies reveal the role that miRNAs have in the regulation of secondary metabolic pathways [20]. Therefore, the production of compounds derived from secondary metabolism can be managed through the miRNAs.…”

Endogenous plant metabolites against insects

“…However, evidence is accumulating that also specialised metabolite biosynthesis is a target for sRNA-based regulation. Although the involvement of various sRNAs in specialised metabolism in multiples species has been predicted computationally (Bulgakov and Avramenko 2015;Gupta et al 2017), only a few of them have actually been experimentally validated (Table 3). miRNA156b appears to be a master regulator of specialised metabolism, involved in terpene, flavonol and anthocyanin biosynthesis in Arabidopsis through targeting SPL9-type TFs (Yu et al 2015;Gou et al 2011).…”