Tuscan Varieties of Sweet Cherry Are Rich Sources of Ursolic and Oleanolic Acid: Protein Modeling Coupled to Targeted Gene Expression and Metabolite Analyses

The potential of six ancient Tuscan sweet cherry (Prunus avium L.) varieties as a source of health-promoting pentacyclic triterpenes is here evaluated by means of a targeted gene expression and metabolite analysis. By using a sequence homology criterion, we identify five oxidosqualene cyclase genes (OSCs) and three cytochrome P450s (CYP85s) that are putatively involved in the triterpene production pathway in sweet cherries. We performed 3D structure prediction and induced-fit docking using cation intermediates and reaction products for some OSCs to predict their function. We show that the Tuscan varieties have different amounts of ursolic and oleanolic acids and that these variations are related to different gene expression profiles. This study stresses the interest of valorizing ancient fruits as alternative sources of functional molecules with nutraceutical value. It also provides information on sweet cherry triterpene biosynthetic genes, which could be the object of follow-up functional studies.

Boosting 11-oxo-β-amyrin and glycyrrhetinic acid synthesis in Saccharomyces cerevisiae via pairing novel oxidation and reduction system from legume plants

Glycyrrhetinic acid (GA) and its precursor, 11-oxo-β-amyrin, are typical triterpenoids found in the roots of licorice, a traditional Chinese medicinal herb that exhibits diverse functions and physiological effects. In this study, we developed a novel and highly efficient pathway for the synthesis of GA and 11-oxo-β-amyrin in Saccharomyces cerevisiae by introducing efficient cytochrome P450s (CYP450s: Uni25647 and CYP72A63) and pairing their reduction systems from legume plants through transcriptome and genome-wide screening and identification. By increasing the copy number of Uni25647 and pairing cytochrome P450 reductases (CPRs) from various plant sources, the titers of 11-oxo-β-amyrin and GA were increased to 108.1 ± 4.6mg/L and 18.9 ± 2.0mg/L, which were nearly 1422-fold and 946.5-fold higher, respectively, compared with previously reported data. To the best of our knowledge, these are the highest titers reported for GA and 11-oxo-β-amyrin from S. cerevisiae, indicating an encouraging and promising approach for obtaining increased GA and its related triterpenoids without destroying the licorice plant or the soil ecosystem.

Production of oleanolic acid glycosides by hairy root established cultures of Calendula officinalis L

In order to initiate hairy root culture initiation cotyledons and hypocotyls of Calendula officinalis L. were infected with Agrobacterium rhizogenes strain ATCC 15834 or the same strain containing pCAMBIA 1381Z vector with β-glucuronidase reporter gene under control of promoter of NIK (Nematode Induced Kinase) gene. The efficiency of induction of hairy roots reached 33.8% for cotyledons and 66.6% for hypocotyls together for both transformation experiments. Finally, eight control and nine modified lines were established as a long-term culture. The hairy root cultures showed the ability to synthesize oleanolic acid mainly (97%) as glycosides; control lines contained it at the average 8.42 mg · g(-1) dry weight in tissue and 0.23 mg · dm(-3) in medium; modified lines: 4.59 mg · g(-1) for the tissue, and 0.48 mg · dm(-3) for the medium. Additionally lines showed high positive correlation between dry/fresh weight and oleanolic acid concentration in tissue. Using the Killiani mixture in acidic hydrolysis of oleanolic acid glycosides released free aglycones that were partially acetylated in such conditions.

Genetic and chemical analysis of a key biosynthetic step for soyasapogenol A, an aglycone of group A saponins that influence soymilk flavor

Although certain saponins in soybean seeds have been reported to have health benefits, group A acetyl saponins cause undesirable bitter and astringent tastes in soy products. Therefore, reduction or elimination of group A saponins is an important target for soybean breeders. A wide survey of cultivated and wild soybean germplasm identified a mutant line that lacked group A saponins. The absence of soyasapogenol A, a group A saponin aglycone, is controlled by a single recessive allele, sg-5 that mapped genetically near the SSR marker, Satt117, on soybean chromosome 15 (linkage group E). The locus is epistatic to Sg-1, which controls the terminal sugar variation on the C-22 sugar chain of soyasapogenol A, and allelic differences at this locus lead to changes in the amount of DDMP saponins and their derivatives group B and E products. These findings provide a new insight into the biosynthetic pathway of soybean saponins, and identify a genetic approach that can be applied to improve the quality of foods produced from soybean.

Composition and physiological function of the wax layers coating Arabidopsis leaves: β-amyrin negatively affects the intracuticular water barrier

Plants prevent dehydration by coating their aerial, primary organs with waxes. Wax compositions frequently differ between species, organs, and developmental stages, probably to balance limiting nonstomatal water loss with various other ecophysiological roles of surface waxes. To establish structure-function relationships, we quantified the composition and transpiration barrier properties of the gl1 mutant leaf waxes of Arabidopsis (Arabidopsis thaliana) to the necessary spatial resolution. The waxes coating the upper and lower leaf surfaces had distinct compositions. Moreover, within the adaxial wax, the epicuticular layer contained more wax and a higher relative quantity of alkanes, whereas the intracuticular wax had a higher percentage of alcohols. The wax formed a barrier against nonstomatal water loss, where the outer layer contributed twice as much resistance as the inner layer. Based on this detailed description of Arabidopsis leaf waxes, structure-function relationships can now be established by manipulating one cuticle component and assessing the effect on cuticle functions. Next, we ectopically expressed the triterpenoid synthase gene AtLUP4 (for lupeol synthase4 or β-amyrin synthase) to compare water loss with and without added cuticular triterpenoids in Arabidopsis leaf waxes. β-Amyrin accumulated solely in the intracuticular wax, constituting up to 4% of this wax layer, without other concomitant changes of wax composition. This triterpenoid accumulation caused a significant reduction in the water barrier effectiveness of the intracuticular wax.

Overexpression of a grapevine R2R3-MYB factor in tomato affects vegetative development, flower morphology and flavonoid and terpenoid metabolism

Although the terpenoid pathway constitutes, with the phenylpropanoid metabolism, the major pathway of secondary metabolism in plants, little is known about its regulation. Overexpression of a Vitis vinifera R2R3-MYB transcription factor (VvMYB5b) in tomato induced pleiotropic changes including dwarfism, modified leaf structure, alterations of floral morphology, pigmented and glossy fruits at the "green-mature" stage and impaired seed germination. Two main branches of secondary metabolism, which profoundly influence the organoleptic properties of the fruit, were affected in the opposite way by VvMYB5b overexpression. Phenylpropanoid metabolism was down regulated whereas the amount of beta-carotene was up regulated. This is the first example of the independent regulation of phenylpropanoid and carotenoid metabolism. The strongest modification concerns a decrease in beta-amyrin, the precursor of the oleanolic acid, which is the major component of grape waxes. Scanning electron microscopy analysis of fruits and leaves confirms the alteration of wax metabolism and a modification of cell size and shape. This may potentially impact resistance/tolerance to biotic and abiotic stresses. The results are compared with a similar approach using heterologous expression of VvMYB5b in tobacco.