In silico analysis, expression profiling and correlation of miRNAs targeting genes of steviol glycosides biosynthesis with steviol glycosides contents in different tissues of Stevia rebaudiana

Study of gene regulation via the action of specific microRNAs has experienced a boom in recent years. Their proven promising role in regulating biosynthetic pathways related gene networks may hold the key to understanding the genetic regulation of these pathways that can help in selection and manipulation to get high performing plant genotypes with better secondary metabolites yields and increased biomass. No experimentally validated research activity has been reported for exploring the miRNA repertoire to understand the regulation of the genes involved in steviol glycosides biosynthetic pathway. In this study, we for the first time identified miRNAs targeting genes of steviol glycosides biosynthetic pathway, whose precursors were potentially generated from ESTs and nucleotide sequences of Stevia rebaudiana. Thereafter, stem-loop coupled real time PCR-based expressions of these miRNAs in different tissues of Stevia rebaudiana were investigated and correlated with steviol glycosides contents. All the miRNAs investigated, showed differential expressions in all the three tissues studied, viz., leaves, flowers and stems. Out of eleven miRNAs validated, the expression levels of nine miRNAs (miR319a, miR319b, miR319c, miR319 d, miR319e, miR319f, miR319h, miRstv_7, miRstv_9) were found to be inversely correlated, while expression levels of the two, i.e. miR319 g and miRstv_11 showed direct correlation with the steviol glycosides contents in leaf, flower and stem tissues. This study, thus, provides a platform for better understanding of the steviol glycosides biosynthetic pathway and these miRNAs can further be employed to manipulate the biosynthesis of these metabolites to enhance their contents and yield in Stevia rebaudiana.