Abstract
Stevia is a natural source of commercially important steviol glycosides (SGs), which share biosynthesis route with gibberellic acids (GAs) through plastidal MEP and cytosolic MVA pathways. Ontogeny-dependent deviation in SGs biosynthesis is one of the key factor for global cultivation of Stevia, has not been studied at transcriptional level. To dissect underlying molecular mechanism, we followed a global transcriptome sequencing approach and generated more than 100 million reads. Annotation of 41,262 de novo assembled transcripts identified all the genes required for SGs and GAs biosynthesis. Differential gene expression and quantitative analysis of important pathway genes (DXS, HMGR, KA13H) and gene regulators (WRKY, MYB, NAC TFs) indicated developmental phase dependent utilization of metabolic flux between SGs and GAs synthesis. Further, identification of 124 CYPs and 45 UGTs enrich the genomic resources, and their PPI network analysis with SGs/GAs biosynthesis proteins identifies putative candidates involved in metabolic changes, as supported by their developmental phase-dependent expression. These putative targets can expedite molecular breeding and genetic engineering efforts to enhance SGs content, biomass and yield. Futuristically, the generated dataset will be a useful resource for development of functional molecular markers for diversity characterization, genome mapping and evolutionary studies in Stevia.
Highlights
Plants are rich and vital source of a large variety of pharmaceutically and industrially important natural metabolites[1]
The raw reads of Illumina sequencing for all the samples have been deposited in National Centre for Biotechnology Information (NCBI) Sequence Read Archive (SRA) with accession number SRP094030 under BioProject PRJNA355055
Comparative leaf transcriptome demonstrates the advantages of high throughput genomics to accelerate the genome-wide ascertainment of the key gene(s) and regulators for the dissection of complex developmental phase transitions involved in steviol glycosides (SGs) biosynthesis in Stevia
Summary
Plants are rich and vital source of a large variety of pharmaceutically and industrially important natural metabolites[1]. (Stevia, family-Asteraceae), is a shrubby, perennial plant species[2], popular worldwide for its ability to accumulate considerably high level of several commercially important steviol glycosides (SGs; up to ~20% of total dry weight)[3,4]. These SGs have been used as an alternative natural sweetener and are effective for controlling important modern lifestyle diseases (diabetes, obesity, cardiac blockage and hypertension)[5,6]. Global transcriptome sequencing approach was adopted to understand the effect of developmental phase transitions on the expression of the genes required for SGs biosynthesis. The current study will provide a comprehensive genomic resource for manipulating SGs accumulation through genetic engineering, and implementation of molecular breeding approaches for dissection of major agronomic traits and varietal improvement programs in Stevia
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