Kexuan Tang

Cordyceps fungi: natural products, pharmacological functions and developmental products

Objectives Parasitic Cordyceps fungi, such as Cordyceps sinensis, is a parasitic complex of fungus and caterpillar, which has been used for medicinal purposes for centuries particularly in China, Japan and other Asian countries. This article gives a general idea of the latest developments in C. sinensis research, with regard to the active chemical components, the pharmacological effects and the research and development of products in recent years.

Bioactive natural products from endophytes: A review

Endophytes, microorganisms that reside in the internal tissues of living plants without causing any immediate overt negative effects, have been found in every plant species examined to date and recognized as potential sources of novel natural products for exploitation in medicine, agriculture, and industry with more and more bioactive natural products isolated from the microorganisms. In this review, we focus mainly on bioactive natural products from endophytic microorganisms by their different functional roles. The prospect and facing problems of isolating natural products from endophytes are also discussed.

Prediction of protein structural class with Rough Sets

BackgroundA new method for the prediction of protein structural classes is constructed based on Rough Sets algorithm, which is a rule-based data mining method. Amino acid compositions and 8 physicochemical properties data are used as conditional attributes for the construction of decision system. After reducing the decision system, decision rules are generated, which can be used to classify new objects.ResultsIn this study, self-consistency and jackknife tests on the datasets constructed by G.P. Zhou (Journal of Protein Chemistry, 1998, 17: 729–738) are used to verify the performance of this method, and are compared with some of prior works. The results showed that the rough sets approach is very promising and may play a complementary role to the existing powerful approaches, such as the component-coupled, neural network, SVM, and LogitBoost approaches.ConclusionThe results with high success rates indicate that the rough sets approach as proposed in this paper might hold a high potential to become a useful tool in bioinformatics.

Increased vitamin C content accompanied by an enhanced recycling pathway confers oxidative stress tolerance in Arabidopsis.

Vitamin C (L-ascorbic acid, AsA) has important antioxidant and metabolic functions in both plants and animals. Once used, ascorbic acid can be regenerated from its oxidized form in a reaction catalyzed by dehydroascorbate reductase (DHAR, EC 1.8.5.1). To analyze the physiological role of DHAR catalyzing the reduction of DHA to ascorbate in environmental stress adaptation, we examined whether increasing the level of AsA through enhanced AsA recycling would limit the deleterious effects of oxidative stress. A chimeric construct consisting of the double CaMV35S promoter fused to the Myc-dhar gene was introduced into Arabidopsis thaliana. Transgenic plants were biochemically characterized and tested for responses to oxidative stress. Western blot indicated that the dhar-transgene was successfully expressed. In homozygous T(4) transgenic seedlings, DHAR overexpression was increased up to 1.5 to 5.4 fold, which enhanced foliar ascorbic acid levels 2- to 4.25-fold and ratio of AsA/DHA about 3- to 16-fold relative to wild type. In addition, the level of glutathione, the reductant used by DHAR, also increased as did its redox state. When whole plants were treated with high light and high temperature stress or in vitro leaf discs were subjected to 10 muM paraquat, transgenic plants showed a larger AsA pool size, lower membrane damage, and a higher level of chlorophyll compared with controls. These data suggested that increasing the plant vitamin C content through enhanced ascorbate recycling could limit the deleterious effects of environmental oxidative stress.

Development of transgenic Artemisia annua (Chinese wormwood) plants with an enhanced content of artemisinin, an effective anti-malarial drug, by hairpin-RNA-mediated gene silencing.

Artemisinin is an effective anti‐malarial drug isolated from Artemisia annua L. (Chinese wormwood), but the content of artemisinin in A. annua is low. In the present study we explored the possibility of using genetic engineering to increase the artemisinin content of A. annua by suppressing the expression of SQS (squalene synthase), a key enzyme of sterol pathway (a pathway competitive with that of artemisinin biosynthesis) by means of a hairpin‐RNA‐mediated RNAi (RNA interference) technique. A total of 23 independent transgenic A. annua plants were obtained through Agrobacterium tumefaciens‐mediated transformation, which was confirmed by PCR and Southern‐blot analyses. HPLC‐evaporative light‐scattering detection analysis showed that the artemisinin content of some transgenic plants was significantly increased, with the highest values reaching 31.4 mg/g dry weight, which is about 3.14‐fold the content observed in untransformed control plants. Real‐time reverse transcription–PCR analysis demonstrated that the expression of SQS was suppressed significantly, and GC–MS analysis showed that sterol was efficiently decreased in the transgenic plants. The present study demonstrated that genetic‐engineering strategy of RNAi is an effective means of increasing artemisinin content in plants.

A review: recent advances and future prospects of taxol-producing endophytic fungi

In the urgent search for more effective ways to treat cancer, new extraction methods of taxol from endophytic fungus have demonstrated high potential in increasing the efficiency of taxol extraction for more efficient and sustainable production of taxol and cancer treatment products. This paper summarizes recent advances in taxol-producing endophytic fungi, both in China and abroad, in the following areas: isolation and identification of endophytic fungi types, extraction and detection methods of endophytic taxol in plants, and improved efficiency of the extraction process. With the advancement of science and technology, new techniques in biotechnology, such as fungal strain improvement and recombining technique and microbial fermentation engineering, have increased the extraction yield from taxol-producing fungi, thereby improved the overall efficiency of taxol production.

CBF-dependent signaling pathway: a key responder to low temperature stress in plants.

Plants under low temperature (LT) stress exhibit a C-repeat binding factor (CBF)-dependent responsive pathway. The transcription factors in the CBF family, existing in multiple plant species, are the key regulators of the cold-responsive (COR) genes. CBF1 and CBF3 are regulated in a different way from CBF2, and CBF4 is the only known CBF gene definitely involved in abscisic acid (ABA)-dependent signaling pathways. RAP2.1 and RAP2.6 are the downstream regulators under CBFs. The upstream regulators of the CBF named inducer of CBF expression (ICE) acts as a positive regulator of CBFs. Meanwhile, these CBF signaling pathway components could associate with many other transcription activators and repressors in regulating gene expression when plants are under LT stress. HOS1 negatively regulates ICE1, which down regulates MYB15, an upstream repressor of CBFs. ZAT12 participates in the repression of CBFs, while ZAT10 and FRY2 negatively regulate the CBF-target genes. ADF5 was recently also found to repress CBFs. LOS2 works against ZAT10, and LOS4 positively regulates CBFs. SFR6 is involved in the modification of CBFs to activate the COR genes, and SIZ1-dependent sumoylation plays a positive role in the regulation of ICE1. The utilization of CBF-dependent signaling components has a broad perspective in the field of plant breeding for enhancing crop LT tolerance.

Rapid Isolation of High‐Quality Total RNA from Taxus and Ginkgo

Abstract An easy and efficient protocol was developed for isolating good‐quality total RNA from various tissues including fruits, leaves, stems, and roots of ancient gymnosperm species, taxus and ginkgo. The protocol was developed based on the CTAB method with modifications, including higher‐strength CTAB to help the lysis of plant cells, more PVP, and β‐mercaptoethanol to prevent oxidation of phenolic complexes, and higher‐centrifugation force to get rid of most cell debris and to ensure RNA quality. In RNA isolation, chloroform/isoamyl alcohol was used to remove proteins, genomic DNA, and secondary metabolites and lithium chloride was subsequently adopted to concentrate total RNA away from most of the cytoplasmic components. Good‐quality total RNA from various tissues of native taxus and ginkgo could be easily isolated within 24 hr by this protocol which avoided the limitation of plant materials and the usage of dangerous chemicals, such as phenol, and could provide total RNA for all kinds of further molecular studies.

Ganodermataceae: Natural Products and Their Related Pharmacological Functions

The objective of this paper is to review the natural products and the pharmacological functions of Ganodermataceae family. Presently, studies on the bioactive components of Lingzhi are focused on polysaccharides and triterpenes/triterpenoids compounds. New Ganoderma polysaccharides, including their molecular weights, glycosyl residue compositions, glycosyl linkage and branches, are summarized in this paper. Also presented are new types of triterpenes and their characteristics from Lingzhi. Taking Ganoderma lucidum as an example, we reviewed its pharmacological functions in anti-tumor and immune-modulating activities for treating hypoglycemosis, hepatoprotection, and the effect on blood vessel system. Based on the advances in Lingzhi research in the past few decades, both G. lucidum and G. sinense are considered as the representative species of medicinal mushroom Lingzhi in China. Until 2001, G. tsugae was only advised to be used as the materials of the health products. The biologically-active components related to pharmacological functions of these three species were studied more than other Ganodermataceae family species; however, which have been used in less modern folk medicine.

Particle-bombardment-mediated co-transformation of elite Chinese rice cultivars with genes conferring resistance to bacterial blight and sap-sucking insect pests

Abstract. Transgenic rice plants were generated using particle bombardment to simultaneously introduce the rice Xa21 gene effective against bacterial blight and the Galanthus nivalis agglutinin (snowdrop lectin; gna) gene effective against sap-sucking insect pests, specifically the brown plant hopper. Using three plasmids, we co-transformed 5- to 10-d-old, mature seed-derived rice (Oryza sativa L.) callus of two elite Chinese rice cultivars, Eyi 105 and Ewan 5. The plasmids carried a total of four genes. The gna and Xa21 genes were carried on separate plasmids. The selectable marker hygromycin phosphotransferase (hpt) and the reporter gene β-glucuronidase (gusA) were linked on the same, co-integrate vector. We recovered over 160 independently derived transgenic rice plants. Over 70% of the transgenic plants carried all four genes, as confirmed by polymerase chain reaction and/or Southern blot analysis. Furthermore, 70% of transgenic plants carrying all four genes also co-expressed all four genes, as confirmed by growth on selection media (hpt), GUS histochemical assays (gusA), western blotting (gna) and reverse transcriptase-polymerase chain reaction (Xa21) analysis. The co-expression efficiency reported for the four transgenes in our study is the highest ever found in any transgenic plant population generated through co-transformation. The linked genes (hpt and gusA) co-integrated with a frequency of near 100%, and we observed a co-integration frequency greater than 70% for the genes carried on separate plasmids. We observed no preferential integration of any particular gene(s). Genetic analysis confirmed Mendelian segregation of the transgenes in subsequent generations. We report, for the first time, generation and analysis of transgenic rice lines carrying genes effective against more than one taxa of pathogen or pest, substantiating that particle bombardment represents an effective way to introduce unlinked complex multiple traits into plants.