Phytoestrogens

Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens

Isoliquiritigenin, a Strong nod Gene- and Glyceollin Resistance- Inducing Flavonoid from Soybean Root Exudate

Isoflavonoid signal molecules from soybean (Glycine max (L.) Merr.) seed and root exudate induce the transcription of nodulation (nod) genes in Bradyrhizobium japonicum. In this study, a new compound with symbiotic activity was isolated from soybean root exudate. The isolated 2',4',4-trihydroxychalcone (isoliquiritigenin) is characterized by its strong inducing activity for the nod genes of B. japonicum. These genes are already induced at concentrations 1 order of magnitude below those required of the previously described isoflavonoid inducers genistein and daidzein. Isoliquiritigenin is also a potent inducer of glyceollin resistance in B. japonicum, which renders this bacterium insensitive to potentially bactericidal concentrations of glyceollin, the phytoalexin of G. max. No chemotactic effect of isoliquiritigenin was observed. The highly efficient induction of nod genes and glyceollin resistance by isoliquiritigenin suggests the ecological significance of this compound, although it is not a major flavonoid constituent of the soybean root exudate in quantitative terms

Senyawa Isoflavonoid Terisoprenilasi dari Ranting Flemingia macrophylla

Flemingia macrophylla merupakan tumbuhan perdu yang termasuk keluarga Fabaceae. Senyawa fenolik Flemingia mengandung senyawa flavonoid dan isoflavonoid. Penelitian ini bertujuan untuk menentukan aktivitas sitotoksik senyawa isoflavonoid dari Flemingia macrophylla terhadap sel kanker payudara T47D. Ekstraksi dan isolasi senyawa isoflavonoid menggunakan metanol pada suhu kamar. Dua senyawa isoflavonoid terisoprenilasi, 8-(1.1-dimetil-prop-2-enil) genistein (1) dan osajin (2) telah berhasil dipisahkan dari ranting Flemingia macrophylla. Penentuan struktur senyawa isoflavonoid menggunakan data spektroskopi ultraviolet (UV), inframerah (IR), 1D dan 2D NMR. Sitotoksik 8-(1.1-dimetil-prop-2-enil) genistein (1) dan osajin (2) terhadap sel kanker payudara T47D memperlihatkan nilai IC50 sebesar 10,91 ± 0,17 dan 3,72 ± 0,23 µg/mL

Soybean isoflavonoid biosynthesis: constituents and circumstance at the transcriptomic and molecular levels

Isoflavonoids are specialized metabolites, almost exclusive to the legume family of plants. They are actors in symbiosis with nitrogen-fixing bacteria and in plant stress response. Isoflavonoids are noted for their human health benefits. Isoflavonoid content in legumes has proven to be a complex trait. The goal of the present research is to determine the mechanisms underlying isoflavonoid biosynthesis in soybean. The first approach was to unravel the genetic factors of isoflavonoid biosynthesis. A branch-point enzyme of the phenylpropanoid pathway, chalcone isomerase (CHI), catalyzes the reaction producing flavanones, the nucleus for many downstream metabolites such as isoflavonoids. I identified twelve soybean CHI genes, including five new members. The evolutionary history of the family shows that the enzymatic fold evolved from being catalytically inactive to being a chalcone-to-flavanone isomerase. Four CHIs in soybean were identified with the latter functionality. The CHIs showed differential temporal and spatial expression, pointing to the potential function of CHI1A in soybean seed isoflavonoid production. On the molecular level of organization, the long-postulated model of a subcellular isoflavonoid enzyme complex forming at the surface of the endoplasmic reticulum (ER) was substantiated in the present study. Here, I identified key players in the ‘metabolon’, established in planta subcellular localization, and investigated protein-protein interaction. The results suggest that isoflavone synthase (IFS), a cytochrome P450, is a nucleating metabolic center at the surface of the ER, interacting with upstream pathway enzymes. Finally, a transcriptomic study was undertaken to find genetic elements linked with isoflavonoid content variation in four soybean cultivars. The results suggest that competing branches of the phenylpropanoid pathway are combinatorially regulated to coordinate flux into isoflavonoid biosynthesis. The candidate genes encode enzymes in the overlapping pathways, several transcription factors, metabolic transporters and more. Study of the CHI gene family and isoflavonoid biosynthesis has provided us with new insights into production and regulation of this important plant natural product. This knowledge can facilitate the manipulation of metabolic content and composition in legumes, and introduction of the isoflavonoid pathway into non-legume crops

Competitiveness and communication for effective inoculation byRhizobium, Bradyrhizobium and vesicular-arbuscular mycorrhiza fungi

After a short summary on the ecology and rhizosphere biology of symbiotic bacteria and vesicular-arbuscular (VA) mycorrhiza fungi and their application as microbial inocula, results on competitiveness and communication are summarized. Stress factors such as high temperature, low soil pH, aluminium concentrations and phytoalexins produced by the host plants were studied withRhizobium leguminosarum bv.phaseoli andRhizobium tropici onPhaseolus beans. Quantitative data for competitiveness were obtained by usinggus + (glucoronidase) labelled strains, which produce blue-coloured nodules. ForPhaseolus-nodulating rhizobia, a group specific DNA probe was also developed, which did not hybridize with more than 20 other common soil and rhizosphere bacteria. Results from several laboratories contributing to knowledge of signal exchange and communication in theRhizobium/Bradyrhizobium legume system are summarized in a new scheme, including also defense reactions at the early stages of legume nodule initiation. Stimulating effects of flavonoids on germination and growth of VA mycorrhiza fungi were also found. A constitutive antifungal compound in pea roots, -isoxazolinonyl-alanine, was characterized

Communication and signal exchange in the Rhizobium bradyrhizobium legume system

A new comprehensive communication concept in the Rhizobium/Bradyrhizobium legume symbiosis was developed. It includes a root zone specific flavonoid exudation, the differential activity of phenylpropane/acetate pathway derivatives on chemotaxis, nod-gene inducing activity and phytoalexin resistance induction on the microsymbiont side (Bradyrhizobium). Nod factor production from the microsymbiont affects the host plant in root hair curling and meristem induction. Phytoalexin production in the host plant is also an early response, however repressed to a low level after a few hours. Another strategy of the microsymbiont to overcome phytoalexin effects is degradation of phytoalexins in Rhizobium leguminosarum bv. vicieae. Competitiveness within the same infection group of the microsymbiont was studied with gus-gene fusion, using the blue coloured nodules to easily discriminate marked strains from unmarked competitors. New exopolysaccharide (EPS) mutants of Bradyrhizobium japonicum were reconstructed homologous with a DNA region to exoB gene of Rhizobium meliloti. Their clearly reduced competitiveness of nodulation, demonstrates that exopolysaccharides of Bradyrhizohium japonicum also have an important function during the early stages of this symbiotic interaction

GmMYB176 Interactome and Regulation of Isoflavonoid Biosynthesis in Soybean

MYB transcription factors are one of the largest transcription factor families characterized in plants. They are classified into four types: R1 MYB, R2R3 MYB, R3 MYB and R4 MYB. GmMYB176 is an R1MYB transcription factor that regulates Chalcone synthase (CHS8) gene expression and isoflavonoid biosynthesis in soybean. Silencing of GmMYB176 suppressed the expression of the GmCHS8 gene and reduced the accumulation of isoflavonoids in soybean hairy roots. However, overexpression of GmMYB176 does not alter either GmCHS8 gene expression or isoflavonoid levels suggesting that GmMYB176 alone is not sufficient for GmCHS8 gene regulation. I hypothesized that GmMYB176 acts cooperatively with another factor(s) for the regulation of GmCHS8 gene expression and it may also regulate other isoflavonoid biosynthetic genes in soybean. The objective of this research was to identify the GmMYB176 interactome for GmCHS8 gene regulation and elucidate the role of GmMYB176 in isoflavonoid biosynthesis in soybean. GmMYB176 interacting proteins were identified using two translational fusion baits (GmMYB176-YFP and YFP-GmMYB176) by co-immunoprecipitation, followed by liquid chromatography-tandem mass spectrometry. The interaction of selected candidates with GmMYB176 was validated in planta and their DNA binding activities determined. GmMYB176 may form a transcriptional complex with Gm04bZIP and/or Gm05bZIP for the regulation of GmCHS8 gene expression. RNA-seq and metabolomics analyses of soybean hairy roots in which GmMYB176 was either silenced or over-expressed revealed that GmMYB176 regulates multiple genes in the isoflavonoid biosynthesis pathway, affecting the production of metabolites in phenylpropanoid pathway such as phenylalanine, liquiritigenin, daidzin, genistin, glycitein, and glyceollin. The knowledge and information generated on the role of GmMYB176 in the regulation of isoflavonoid biosynthesis will allow genetic manipulation of isoflavonoid level in soybean and/or introduce isoflavonoid pathway in non-legumes