Seeds of Stevia rebaudiana Bertoni as a Source of Plant Growth-Promoting Endophytic Bacteria with the Potential to Synthesize Rebaudioside A

Abstract

In this study, a new strain of Pantoea vagans, SRS89, was isolated from surface-sterilized stevia seeds. The isolate was evaluated using morphological, molecular, and biochemical methods. The bacterium was 1.5 μm long, yellowish in color, and classified as Gram-negative. Whole genome sequencing of our strain revealed the presence of a 4,610,019 bp chromosome, and genome annotation resulted in the detection of 4283 genes encoding 4204 putative coding sequences. Phylogenic analysis classified the genome of our strain close to the MP7 and LMG 24199 strains of P. vagans. Functional analysis showed that the highest number of genes within the analyzed bacterium genome were involved in transcription, amino acid transport and metabolism, and carbohydrate transport and metabolism. We also identified genes for enzymes involved in the biosynthesis of carotenoids and terpenoids. Furthermore, we showed the presence of growth regulators, with the highest amount noted for gibberellic acid A3, indole-3-acetic acid, and benzoic acid. However, the most promising property of this strain is its ability to synthesize rebaudioside A; the estimated amount quantified using reversed-phase (RP)-HPLC was 4.39 mg/g of the dry weight of the bacteria culture. The isolated endophytic bacterium may be an interesting new approach to the production of this valuable metabolite.

Pantoea vagans causing soft rot disease in Agave angustifolia, in Mexico

“…The P. vagans strain SRS89 isolated stevia seeds by Simlat et al. (2023) synthesized several types of growth regulators of great importance for plant growth, among which GA3 was the most abundant and jasmonic acid.…”

Microbial fortification of pharmacological metabolites in medicinal plants

“…Treatments of S. rebaudiana with Enterobacter hormaechei strains H2A3 and H5A2, which were isolated from the S. rebaudiana endosphere, resulted in increased steviol glycosides contents and the transcript upregulation of the steviol glycosides biosynthesis genes including KO , KAH , UGT74G1 , and UGT76G1 [42] . Interestingly, bacterial synthesis of rebaudioside A was observed for a strain of Pantoea vagans that was endophytic to S. rebaudiana seeds [43] . Thus, the microbe-increased accumulation of steviol glycosides in the S. rebaudiana plants might also be contributed directly by the presence of the microbes.…”

Genomic mechanisms of plant growth-promoting bacteria in the production of leguminous crops

“…With recent progression in molecular technology, various gene technological data, including genomics, metagenomics, transcriptomics, and proteomics data, are uploaded on global websites (Lata et al, 2023). Genomic sequence analysis of PGPR is grouped into two groups, and they are whole genome sequencing (WGS) and specific genome sequencing (SGS) (Simlat et al, 2023).…”