biosynthesis-flavonol-from-flavanone-establishing-one-pot-bienzymatic

Biosynthesis of a Flavonol from a Flavanone by Establishing a One-pot Bienzymatic Cascade

Flavonols are a major subclass of flavonoids with a variety of biological and pharmacological activities. Here, we provide a method for the in vitro ...

yangzhou university

Yangzhou University

In cucumber (Cucumis sativus L.), the preexisting fruits inhibit the growth of subsequent fruits. To study the mechanism underlying this phenomenon, we examined the sink activity, the level of free sugars, and the activity of SNF1-related protein kinase 1 (SnRK1) in the peduncles of two types of fruits. In the two-fruit cucumber plants, the growth rate and sink activity [evaluated by alkaline alpha-galactosidase (CsAGA) activity in the peduncle] of the first fruit were greater than those of the second fruit. The (14)C-labeling experiment revealed that assimilates produced by the leaves closer to the second fruit tended to move to the first fruit. Sucrose and trehalose-6-phosphate (T6P) levels in the peduncle of the first fruit were higher than those in the peduncle of the second fruit. The SnRK1 activity was lower in the peduncle of the first fruit than in that of the second fruit at 0-8 days after anthesis. The growth rate and sink activity of the second fruit were enhanced after the removal of the first fruit or after treatment with 6-benzyl aminopurine, as determined by comparison with an increase in the sucrose and T6P levels and a decrease in the SnRK1 activity in its peduncle. The SnRK1 activity was inhibited by T6P in an in vitro kinase assay, and the mRNA level of CsAGA1 in cucumber calli was up-regulated by exogenous trehalose treatment, confirming that the SnRK1 activity and CsAGA1 expression can be regulated by T6P levels. Our results suggest that the T6P- and SnRK1-mediated signaling functions are involved in the regulation of first-fruit inhibition in cucumber plants. 

Trehalose-6-phosphate and SNF1-related protein kinase 1 are involved in the first-fruit inhibition of cucumber.

ZrWPO/ZrO composites were fabricated by solid state reaction with the goal of tailoring the thermal expansion coefficient. XRD, SEM and TMA were used to investigate the composition, microstructure, and thermal expansion behavior of ZrWPO/ZrO composites with different mass ratio. Relative densities of all the resulting ZrWPO/ZrO samples were also tested by Archimedes' methods. The obtained ZrWPO/ZrO composites were comprised of orthorhombic ZrWPO and monoclinic ZrO. As the increase of the ZrWPO, the relative densities of ZrWPO/ZrO ceramic composites increased gradually. The coefficient of thermal expansion of the ZrWPO/ZrO composites can be tailored from 4.1 × 10 K to -3.3 × 10 K by changing the content of ZrWPO. The 2:1 ZrWPO/ZrO specimen shows close to zero thermal expansion from 25 to 700°C with an average linear thermal expansion coefficient of -0.09 × 10 K. These adjustable and near zero expansion ceramic composites will have great potential application in many fields.

Synthesis of ZrWPO/ZrO Composites with Adjustable Thermal Expansion.

Raffinose family oligosaccharides (RFOs) accumulate under stress conditions in many plants and have been suggested to act as stress protectants. To elucidate the metabolic process of RFOs under cold stress, levels of RFOs, and related carbohydrates, the expression and activities of main metabolic enzymes and their subcellular compartments were investigated during low-temperature treatment and during the recovery period in cucumber leaves. Cold stress induced the accumulation of stachyose in vacuoles, galactinol in vacuoles and cytosol, and sucrose and raffinose in vacuoles, cytosol, and chloroplasts. After cold stress removal, levels of these sugars decreased gradually in the respective compartments. Among four galactinol synthase genes (CsGS), CsGS1 was not affected by cold stress, while the other three CsGSs were up-regulated by low temperature. RNA levels of acid-α-galactosidase (GAL) 3 and alkaline-α-galactosidase (AGA) 2 and 3, and the activities of GAL and AGA, were up-regulated after cold stress removal. GAL3 protein and GAL activity were exclusively located in vacuoles, whereas AGA2 and AGA 3 proteins were found in cytosol and chloroplasts, respectively. The results indicate that RFOs, which accumulated during cold stress in different subcellular compartments in cucumber leaves, could be catabolized in situ by different galactosidases after stress removal.

Metabolic process of raffinose family oligosaccharides during cold stress and recovery in cucumber leaves.

An in vitro multienzyme synthetic system was developed and optimized to efficiently produce kaempferol in a single reaction tube. Two key genes, Atf3h and Atfls1, in the biosynthetic pathway of kaempferol were cloned into a prokaryotic expression vector and overexpressed in Escherichia coli. The recombinant proteins were purified through affinity chromatography and showed activities of flavanone 3-hydroxylase and flavonol synthase, respectively, followed by development of an in vitro synthetic system for producing kaempferol. The system contains 8.2 mM α-ketoglutaric acid, 0.01 mM ferrous ion, 0.4% sodium ascorbate, 25 μg/mL of each recombinant enzyme, and 10% glycerol in 100 mM Tris-HCl (pH 7.2). When the reaction was carried out at 40 °C for 40-50 min, the yield of kaempferol was 37.55 ± 1.62 mg/L and the conversion rate from NRN to KMF was 55.89% ± 2.74%. Overall, this system provides a promising and efficient approach to produce kaempferol economically.

Development and Optimization of an In Vitro Multienzyme Synthetic System for Production of Kaempferol from Naringenin.

ZrMoPO/ZrO composites were successfully synthesized by the solid state method in attempt to fabricate the near-zero thermal expansion ceramics. The phase composition, micromorphology and thermal expansion behavior of the ZrMoPO/ZrO composites with different mass ratios were investigated using X-ray diffraction, scanning electron microscopy and thermal mechanical analysis. Results indicate that ZrMoPO/ZrO composites can be prepared by pre-sintering at 500°C for 3 h and then sintering at 1050°C for 6 h. The resulting ZrMoPO/ZrO composites consisted of orthorhombic ZrMoPO and monoclinic ZrO. With increasing content of ZrMoPO, the ZrMoPO/ZrO ceramics became more compact and the coefficient of thermal expansion decreased gradually. ZrMoPO/ZrO composites show an adjustable coefficient of thermal expansion (CTE) from 5.57 × 10 K to -5.73 × 10 K by changing the mass ratio of ZrMoPO and ZrO. The ZrMoPO/ZrO composite with a mass ratio of 2:1 showed near zero thermal expansion, and the average linear thermal expansion coefficient is measured to be 0.0065 × 10 K in the temperature range from 25 to 700°C.

Zhiping Zhang

College of Bioscience and Biotechnology

yangzhou university

Biosynthesis of a Flavonol from a Flavanone by Establishing a One-pot Bienzymatic Cascade

Zhiping Zhang

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}College of Bioscience and Biotechnology

yangzhou university

Biosynthesis of a Flavonol from a Flavanone by Establishing a One-pot Bienzymatic Cascade

College of Bioscience and Biotechnology