Candida parapsilosis carbonyl reductases (CpRCR) have been widely used for the reductive conversion of ketone precursors and chiral alcohol products in pharmaceutical industries. The enzymatic enantioselectivity is believed to be related to the shape complementation between the cavities in the enzymes and the substitutions of the ketone substrates. In this work, we reported an unexpected enantioselectivity in the enzyme reductions of dihydrofuran-3(2H)-one (DHF) to (S)-tetrahydrofuran-3-ol (DHF-ol, enantiomeric excess: 96.4%), while dihydrothiophen-3(2H)-one substrate (DHT) was unproductive under the same experimental conditions. To rationalize the exclusive S-configuration and the specific reactivity of DHF, we carried out molecular dynamics simulations for the reacting complexations of DHF with CpRCR, and DHT with CpRCR. Our calculations indicate that DHF preferentially binds to the small cavity near L119, F285, and W286, while the large cavity near the α1 helix was mainly occupied by solvent water molecules. Moreover, the pre-reaction state analysis suggests that the pro-S conformations were more abundant than the pro-R, in particular for DHF. This suggests that the non-polar interaction of substrate C4-C5 methylene contacting the hydrophobic side-chains of L119-F285-W286, and the polar interaction of funanyl oxygen exposing the solvent environment play important roles in the enantioselectivity and reactivity. The phylogenetic tree of CpRCR homologues implies that a variety of amino acid combinations at positions 285 and 286 were available and thereby potentially useful for redesigning enantioselective reductions of 5-membered-ring heterocyclic ketones.
The majority of studies have found that an increase in tree species diversity can increase the productivity of forest stands thanks to complimentary effects with enhanced resource use efficiency or selection effects; however, it is unclear how tree species diversity affects the soil fungal community and enzyme activities in subtropical evergreen forests. In this study, we used soil high-throughput sequencing to investigate the soil fungal community structure and diversity in the central area of tree clusters in the gradient of tree species richness formed by four possible dominant tree species (Pinus massoniana Lamb., Choerospondias axillaris Roxb., Cyclobalanopsis glauca Thunb. and Lithocarpus glaber Thunb.) in subtropical evergreen broad-leaved forest. The results showed that soil organic carbon content and total nitrogen content were significantly higher in mixed tree clusters, and that soil fungal richness and diversity increased with the increase in tree species diversity (1–3 species). Soil acid phosphatase and urease activity were also enhanced with tree species diversity (p < 0.05). The relative abundance of soil symbiotic fungi (ectomycorrhizal fungi) decreased, while the relative abundance of saprotrophic fungi increased. Redundancy analysis (RDA) revealed that soil acid phosphatase activity was the main factor affecting soil fungal communities and functional guilds, and that soil water content was the main driving force behind fungal trophic modes. In subtropical forests, changes in tree species diversity have altered the soil fungal community structure and trophic modes and functions, accelerating the decomposition of organic matter, increasing nutrient cycling, and perhaps also changing the nutrient absorption of trees.
Receptor protein tyrosine phosphatase alpha (RPTPα), an activator of Src family kinases, is found significantly overexpressed in human cancer tissues. However, little is known about the regulation of RPTPα expression. miRNAs target multiple genes and play important roles in many cancer processes. Here, we identified a miRNA, miR-218 that binds directly to the 3'-UTR of RPTPα. Ectopic overexpression of miR-218 decreased RPTPα protein leading to decreased dephosphorylation of c-Src and decreased tumour growth in vitro and in vivo. A feedback loop between c-Src and miR-218 was revealed where c-Src inhibits transcription of SLIT2, which intronically hosts miR-218. These results show a novel regulatory pathway for RPTPα-c-Src signalling.
Carboxylated cellulose nanocrystals (CCN) were prepared from bamboo pulp by ammonium persulfate (APS) with an ultrasonication-assisted technique. The effects of ultrasonication time, APS concentration, and reaction temperature on the yield of CCN were investigated. The morphology, structure, crystallinity, and thermal properties of prepared samples were analyzed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The CCN presented rod-like shapes with diameter ranging from 10 to 30 nm and length of 50 to 200 nm. FTIR showed that CCN still kept with the basic chemical structure of cellulose, and at the 1735 cm-1 appearing the peak of C=O. The XRD pattern indicated that CCN was characteristic of the cellulose I crystal form, and the crystallinity of CCN was 63%. TGA revealed that CCN had a lower thermal stability than bamboo pulp. This research explored a low-cost and eco-friendly way to prepare CCN.
Abstract Dietary specialists consume specific prey items, and they are often morphologically and behaviorally specialized to feed efficiently on those prey animals. Among specialist snakes, consumption of terrestrial arthropods is relatively rare. Because most terrestrial arthropods possess hardened sclerites and appendages, it is possible that snakes that feed on arthropods would show specialized prey-handling behavior. In this study, we describe prey-handling behavior of a snake feeding on terrestrial arthropods, which hitherto has not been well documented. We focused on Rhabdophis chiwen, which mainly feeds on earthworms, but also consumes lampyrine firefly larvae, sequestering cardiotonic steroids from them in its defensive organs, called nucho-dorsal glands. When feeding on earthworms, snakes showed size-dependent selection of swallowing direction, but this tendency was not observed when feeding on firefly larvae. Manipulation of firefly larvae did not seem to be efficient, probably because they possess sclerites and appendages such as legs that impede smooth handling. Although fireflies are an essential food for R. chiwen as a toxin source, our results showed that the snake is not adept at handling firefly larvae compared to earthworms, implying that dietary specialization does not necessarily accompany behavioral specialization. We discuss possible reasons for this inconsistency.
An effective method was established for the simultaneous determination of 51 mycotoxins in over 400 edible oils, in which low-temperature purification and redesigned solid-phase extraction were implicated. Chemometrics technique was utilized to evaluate the interaction effects between variables and to reach the true optimal conditions. As a result, peanut oil and sesame oil were the most contaminated matrices, while the least number of mycotoxins was found in sunflower seed oil and camellia oil. Dietary intake levels of mycotoxins were determined, and the risks were acceptable in most cases. But the ingestion of aflatoxins and alternariol monomethyl ether through edible oils is a cause for concern, confirming the need for further research on the health risk assessment or redefining levels of toxicological concern. Furthermore, based on the distribution and concentration of representative mycotoxins, several interesting criteria for the preliminary identification of certain edible oils have also been proposed by the authors.
Abstract A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of crosses between a series of 2 n = 56 partial amphiploids confirmed that the alien genome of the BYDV‐immune Agro‐tricum line OK7211542 is derived from Thinopyrum ponticum and not from Thinopyrum intermedium. The evidence from meiotic pairing analysis indicated that the chromosome constitution of OK7211542 is similar to another Agrotricum line, ORRPX, which was derived from a cross of wheat and Th. ponticum , but different from other Agrotricum lines, Zhong 5 and TAF 46 which were derived from the crosses between wheat and Th. intermedium. The GISH analysis confirmed that OK7211542 contained one complete set of 14 Th. ponticum chromosomes, in which no S chromosome was present in the alien genome. GISH also detected a small alien translocation attached to one of the wheat chromosomes, a result that was consistent with the pairing data.
Duplication events occur very frequently during plant evolution. The genes in the duplicated pathway or network can evolve new functions through neofunctionalization and subfunctionalization. Flavonoids are secondary metabolites involved in plant development and defense. Our previous transcriptomic analysis of F6 recombinant inbred lines (RILs) and the parent lines after Fusarium oxysporum f. sp. vasinfectum (Fov) infection showed that CHI genes have important functions in cotton. However, there are few reports on the possible neofunctionalization differences of CHI family paralogous genes involved in Fusarium wilt resistance in cotton. In this study, the resistance to Fusarium wilt, expression of metabolic pathway-related genes, metabolite content, endogenous hormone content, reactive oxygen species (ROS) content and subcellular localization of four paralogous CHI family genes in cotton were investigated. The results show that the four paralogous CHI family genes may play a synergistic role in Fusarium wilt resistance. These results revealed a genetic channelization mechanism that can regulate the metabolic flux homeostasis of flavonoids under the mediation of endogenous salicylic acid (SA) and methyl jasmonate (MeJA) via the four paralogous CHI genes, thereby achieving disease resistance. Our study provides a theoretical basis for studying the evolutionary patterns of homologous plant genes and using homologous genes for molecular breeding.
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