Daminozide Enhances Vigor and Steviol Glycoside Yield of Stevia (Stevia rebaudiana Bert.) Propagated in the Temporary Immersion Bioreactor

Stevia (Stevia rebaudiana Bertoni) contains sweet compound widely used as natural sweetener, steviol glycoside (SG). SG is a diterpenoid secondary metabolite synthesized from ent-kaurenoic acid, the same precursor of Gibberellin (GA). Therefore, in this study, a GA inhibitor, Daminozide (0, 10, 20 ppm) was used to block ent-kaurenoic acid conversion towards GA synthesis in attempt to increase SG content of stevia propagated in Temporary Immersion Bioreactor (TIB). Daminozide in 10 mg/L was observed to be the optimum concentration which increased biomass weight and SG content (stevioside and rebaudioside A) up to 40%. The treatment also increased transcripts accumulation of genes enrolled in SG biosynthesis, such as SrKA13H, SrUGT85C2, and SrUGT76G1, indicating SG pathway become more active due to the inhibition of GA pathway. Furthermore, the inhibition of GA was also indicated by the upregulated expression of GA biosynthesis gene (GA3ox) as the result of feedback regulation, and the downregulated expression of GA catabolism gene (GA2ox2) as the result of feed-forward regulation caused by inhibitor treatment.

Hormonal Diterpenoids Distinct to Gibberellins Regulate Protonema Differentiation in the Moss Physcomitrium patens

Plants synthesize gibberellin (GA), a diterpenoid hormone, via ent-kaurenoic acid (KA) oxidation. GA has not been detected in the moss Physcomitrium patens despite its ability to synthesize KA. It was recently shown that a KA metabolite, 3OH-KA, was identified as an active regulator of protonema differentiation in P. patens. An inactive KA metabolite, 2OH-KA, was also identified in the moss, as was KA2ox, which is responsible for converting KA to 2OH-KA. In this review, we mainly discuss the GA biosynthetic gene homologs identified and characterized in bryophytes. We show the similarities and differences between the OH-KA control of moss and GA control of flowering plants. We also discuss using recent genomic studies; mosses do not contain KAO, even though other bryophytes do. This absence of KAO in mosses corresponds to the presence of KA2ox, which is absent in other vascular plants. Thus, given that 2OH-KA and 3OH-KA were isolated from ferns and flowering plants, respectively, vascular plants may have evolved from ancestral bryophytes that originally produced 3OH-KA and GA.

Cytotoxic and genotoxic effects of the ent-kaurenoic acid and ent-kaurenoic acid enriched Mikania glomerata extract in V79

Ferreira NH, Ribeiro AB, Morais MD, Peixoto AM, Bernardino MA, Moreira MR, Soares ACF, Heleno VCG, Veneziani RCS, Tavares DC. 2018. Cytotoxic and genotoxic effects of the ent-kaurenoic acid and ent-kaurenoic acid-enriched Mikania glomerata extract in V79. Biofarmasi J Nat Prod Biochem 17: xxxx. The ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel was effective to inhibit the formation of Streptococcus mutans biofilm. In view of the biological potential of this extract and its major component, the present study was carried out to evaluate the safety of the ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel and ent-kaurenoic acid alone in an in vitro test system. The results showed that the ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel was cytotoxic at concentrations up to 40.0 μg/mL. Genotoxic effects were observed in cell cultures treated with the highest concentrations tested of ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel (10.0 and 15.0 µg/mL) and ent-kaurenoic acid alone (2.5, 5.0 and 7.5 µg/mL) when compared to the control group. Therefore, the ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel demonstrated cytotoxicity and genotoxicity effects at the highest concentrations tested, while ent-kaurenoic acid showed to be genotoxic at the same concentrations present in ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel in V79 cells. These results demonstrate that the ent-kaurenoic acid should be responsible, at least in part, of the genotoxicity of ent-kaurenoic acid-rich extract from Mikania glomerata Sprengel.