Crystal structure of the plant feruloyl-coenzyme A monolignol transferase provides insights into the formation of monolignol ferulate conjugates.

Lignin is a highly complex phenolic polymer which is essential for plants, but also makes it difficult for industrial processing. Engineering lignin by introducing relatively labile linkages into the lignin backbone can render it more amenable to chemical depolymerization. It has been reported that introducing a feruloyl-coenzyme A monolignol transferase from Angelica sinensis (AsFMT) into poplar could incorporate monolignol ferulate conjugates (ML-FAs) into lignin polymers, suggesting a promising way to manipulate plants for readily deconstructing. FMT catalyzes a reaction between monolignols and feruloyl-CoA to produce ML-FAs and free CoA-SH. However, the mechanisms of substrate specificity and catalytic process of FMT remains poorly understood. Here we report the structure of AsFMT, which adopts a typical fold of BAHD acyltransferase family. Structural comparisons with other BAHD homologs reveal several unique structural features of AsFMT, different from those of the BAHD homologs. Further molecular docking studies showed that T375 in AsFMT may function as an oxyanion hole to stabilize the reaction intermediate and also proposed a role of H278 in the binding of the nucleophilic hydroxyl group of monolignols. Together, this study provides important structural insights into the reactions catalyzed by AsFMT and will shed light on its future application in lignin engineering.

[Effect of heating treatment on stability of two coumarins in Angelica dahurica and activity of tyrosinase].

To study the heating treatment of Angelica dahurica under different temperature and time conditions on the stability of coumarins and tyrosinase activity. HPLC method was used to determine the contents of imperatorin and isoimperatorin, and tyrosinase activity was assayed by measuring the oxidation rate of L-DOPA in vitro. After heated, the contents of imperatorin increased. Expect for being heated at 90 ℃ for 2 h, the content of isoimperatorin was higher than crude one. Before and after being heated, A. dahurica showed an activating effect on tyrosinase. In the same temperature and time conditions, the activation rate increased with the rise of concentration of tyrosinase extracts. Heating process for A. dahurica could change the contents of imperatorin and isoimperatorin, mainly increasing their concentrations.

[Dynamic studies on photosynthetic and growth characteristics of Angecila dahurcia].

Photosynthetic and growth characteristics of Angelica dahurica were studied in order to clarity the relations of photosynthesis, growth and root dry weight, and provide a theoretical basis for its cultivation. Photosynthesis and growth indexes were meas- ured every 25 days. The contents of chlorophyll a, b, a + b, soluble protein and the activities of Hill reaction, Ca(2+)-ATPase, Mg(2+)-ATPase had an increasing trend; They had the highest value in leaf high-speed growth period. Then, they were decreased in root high- speed growth period. The root dry weight showed negative corelation with photosynthetic characteristics indexes except stomatal con- ductance, however, the negative corelation only from net photosynthetic rate and Ca(2+)-ATPase were significant. The vegetative growth period of spring sowing A. dahuricia was divided into three phases: seedling period, leaf high-speed growth period and root high-speed growth period. The root dry weight showed a significantly positive corelation with the root diameter, leaf dry weight, shoot dry weight, aboveground dry weight. There was the competitive relation between aboveground and underground, so underground growth could be es- timated from leaf area and shoot dimeter.

Cloning and characterization of phenylalanine ammonia-lyase and cinnamate 4-hydroxylase and pyranocoumarin biosynthesis in Angelica gigas.

Phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H) are important enzymes in the phenylpropanoid pathway and also in the accumulation of decursin (1) and decursinol angelate (2), which are major secondary metabolites in Angelica gigas. Using PCR with degenerate primers targeted to conserved regions of available orthologous PAL and C4H sequences, cDNAs encoding PAL and C4H from A. gigas were isolated. Both genes were used to show the comparative developmental and inducible accumulation of mRNAs in different organs and in suspension cells of A. gigas. PAL and C4H were induced most strongly in response to 300 microM methyl jasmonate treatment at 6 and 12 h, respectively, and were highly expressed in the fine roots of A. gigas. Similarly, the production of 1 and 2 was most prolific in the fine roots of the plant.