Electrochemical aptasensor based on DNA-templated copper nanoparticles and RecJf exonuclease-assisted target recycling for lipopolysaccharide detection.

An electrochemical aptasensor for detecting lipopolysaccharides (LPS) was fabricated based on DNA-templated copper nanoparticles (DNA-CuNPs) and RecJf exonuclease-assisted target recycling. The DNA-CuNPs were synthesized on a double-stranded DNA template generated through the hybridization of the LPS aptamer and its complementary chain (cDNA). In the absence of LPS, the CuNPs were synthesized on DNA double-strands, and a strong readout corresponding to the CuNPs was achieved at 0.10 V (vs. SCE). In the presence of LPS, the fabricated aptamer could detach from the DNA double-strand to form a complex with LPS, disrupting the template for the synthesis of CuNPs on the electrode. Meanwhile, RecJf exonuclease could hydrolyze the cDNA together with this single-stranded aptamer, releasing the LPS for the next round of aptamer binding, thereby enabling target recycling amplification. As a result, the electrochemical signal decreased and could be used to indicate the LPS content. The fabricated electrochemical aptasensor exhibited an extensive dynamic working range of 0.01 pg mL-1 to 100 ng mL-1, and its detection limit was 6.8 fg mL-1. The aptasensor also exhibited high selectivity and excellent reproducibility. Moreover, the proposed aptasensor could be used in practical applications for the detection of LPS in human serum samples.

[Effects of earthworm on soil microbes and biological fertility: A review].

Earthworms are considered as 'ecosystem engineers', as they affect soil microbial community and function by improving micro-habitat, increasing surface area of organic compound, feeding, and transporting microorganisms. Multi-scale cavities created through earthworm movements help improve soil porosity and aeration, thus supporting microbial growth and reproduction. Earthworms also break down complex organic compounds into microbe-accessible nutrients by means of feeding on, crushing, and mixing soil. This results in elevated mineralization and improvement of cycling of key soil nutrients including carbon, nitrogen, and phosphorus, overall enhancing the soil biological fertility.

Analysis of genetic variability and population structure of the endemic medicinal Limonium sinense using molecular markers.

Limonium sinense is an endemic medicinal herb used to treat fever, hemorrhage and other disorders. In the present study, population genetic diversity was elucidated using random amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) primers. Percentage of polymorphic bands, Nei's gene diversity and Shannon's information index revealed a high level of genetic diversity at species level. The analysis of molecular variance revealed that 69.88% (RAPD), 71.19% (ISSR) and 70.97% (AFLP) of variability were partitioned among individuals within populations, which indicated the coherent trend by Gst (0.3849/0.3577/0.3670). Gene flow number (Nm) was 0.581/0.618/0.612, which indicated that there was a limited gene exchange between populations. The UPGMA clustering results showed that the genetic distance had no significant correlation with geographic distance. These results indicate that these markers were reliable tools for the differentiation and determination of the genetic diversity among the populations of L. sinense and the conservation of existing natural population is necessary.

Genetic diversity across natural populations of Dendrobium officinale, the endangered medicinal herb endemic to China, revealed by ISSR and RAPD markers.

Dendrobium officinale is a rare and endangered herb with special habitats and endemic to China. Genetic diversity was examined within and among nine natural populations using inter-simple sequence repeat (ISSR) and random amplified polymorphic (RAPD) for conservation. Both molecular markers revealed a high percentage (>89%) of polymorphic bands and ISSR markers detected more diversity than RAPD markers. Analysis of molecular variance (AMOVA) revealed that 78.84% (ISSR) and 78.88% (RAPD) of variability was partitioned among individuals within populations. This genetic structure was probably due to severe genetic drift resulting from habitat fragmentation and human overexploitation since 1950s. Moreover, there is a lack of significant association between genetic and geographic distances (r = 0.276; p > 0.05) in the populations of D. officinale. From the conservation point of view, populations GL, GS and GSD with higher genetic diversity should be protected firstly to maintain the species potential for evolutionary change and population YG with lower diversity but representing a novel evolutionary unit should also be paid more attention to during D. officinale conservation practice.

Molecular authentication of Dendrobium loddigesii Rolfe by Amplification Refractory Mutation System (ARMS).

As a widely used medicinal plant, Dendrobium loddigesii Rolfe is always a possible target for fraudulent labeling. The identification of D. loddigesii is generally difficult from its morphological and chemical appearance only. In order to develop a convenient and efficient identification method for D. loddigesii, six pairs of diagnostic ARMS primers were designed based on nrDNA ITS sequences of D. loddigesii and eleven adulterants. The results showed that one diagnostic primer pair (FJB-04-forward, FJB-04-reverse) could be used to authenticate D. loddigesii by generating a fragment of 353 bp at annealing temperatures from 48 degrees C to 62 degrees C while the other diagnostic primer pair (FJB-03-forward, FJB-03-reverse) took on the same effect at annealing temperatures from 49 degrees C to 55 degrees C. This points out the potential of ARMS analysis for authentication of D. loddigesii.

SNP, ARMS and SSH authentication of medicinal Dendrobium officinale KIMURA et MIGO and application for identification of Fengdou drugs.

Dried stems of Dendrobium officinale have been used as crude drugs in traditional Chinese medicine (TCM) with good tonic efficacy. Sequences of chloroplast, nuclear and mitochondria genes and the method of genomic DNA (gDNA) suppression subtraction hybridization (SSH) were used to authenticate different populations during the process of good agriculture practice (GAP) and crude drug quality control. Six populations could be authenticated successfully by nine single sucleotide polymorphism (SNP) sites and six pairs of diagnostic primers for amplification refractory mutation system (ARMS) were also designed to identify six populations on the basis of single nucleotide polymorphism (SNPs). The remainder two populations (JSR, GGL) with the same sequences could be authenticated by SSH. One population-specific fragment was obtained by SSH and a pair of specific primers (SSH-JB01, SSH-JB02) on the specific sequence was designed to authenticate GGL population from the other populations tested. As the resultants were population-specific, the botanic origins of fifty "Fengdou" drug samples from markets could be classified. It is evident that the combined methods provide a high throughput and reliable approach for identification of D. officinale plants and "Fengdou" drugs.

Genetic diversity analysis and conservation of the endangered Chinese endemic herb Dendrobium officinale Kimura et Migo (Orchidaceae) based on AFLP.

Dendrobium officinale is a critically endangered perennial herb endemic to China. Determining the levels of genetic diversity and patterns of population genetic structure of this species would assist in its conservation and management. Data of 12 populations were used to assess its genetic diversity and population structure, employing the method of amplified fragment length polymorphism (AFLP). A high level of genetic diversity was detected (H (E) = 0.269) with POPGENE. As revealed by AMOVA analysis, there was moderate variation between pairs of populations with Phi(ST) values ranging from 0.047 to 0.578 and on average 26.97% of the genetic variation occurred among populations. Three main clusters were shown in UPGMA dendrogram using TFPGA, which is consistent with the result of principal coordinate ananlysis (PCO) using NTSYS. Keeping a stable environment is critical for the in situ conservation and management of this rare and endangered plant, and for ex situ conservation it is important to design an integrated germplasm bank.

Molecular authentication of Alisma orientale by PCR-RFLP and ARMS.

As a widely used medicinal plant, Alisma orientale is always a possible target for fraudulent labeling. The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (nrDNA) of the six species of genus Alisma were sequenced, and two variant sites were found to be specific for A. orientale. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis and amplification refractory mutation system (ARMS) analysis were applied to the ITS region for the identification of A. orientale. A restriction site for PSTI useful for PCR-RFLP analysis was detected and a pair of diagnostic primers DFZX-JB02S and DFZX-JB02X were designed for ARMS.

[Studies on population difference of Dendrobium officinale II establishment and optimization of the method of ISSR fingerprinting marker].

OBJECTIVE: To establish and optimize ISSR-PCR system of Dendrobiwn officinale according to the ISSR-PCR characters of D. officinale. METHOD: The effects of ISSR-PCRs was examined by selecting primers and designing different concentrations of the factors in the ISSR-PCRs, the reliable ISSR-PCR systems for D. officinale populations researching was established by analyzing the reasons for occurrence of differential bands and optimizing reaction conditions. RESULT AND CONCLUSION: The optimal ISSR-PCR system in D. officinale was reported for the first time, and 25 15327012 microL ISSR-PCR system contained 10 x Taq buffer, 1.5 U Taq DNA polymerase, 1.2-1.8 mmol x L(-1) MgCl2, 80 micromol x L(-1) dNTP, 0.2 micro mol x L(-1) primer and 20 ng template DNA. The appropriate annealing temperature was among 52-60 degrees C. ISSR PCRs were significantly influenced by Taq DNA polymerase, template DNA quantity and annealing temperature, etc. The ISSR-PCR systems, which were established in this paper for studying D. officinale, could provide clear reliable abundant polymorphisms molecular markers and were proved suitable for studying population authentication and population molecular ecology of D. officinale.

[Genetic diversity and molecular authentication of wild populations of Dendrobium officinale by RAPD].

AIM: Genetic diversity, relationship and molecular authentication of total 8 wild populations of Dendrobium officinale were investigated using RAPD markers. METHODS: 10 random decamer primers were screened for Random Amplified Polymophic DNA (RAPD) fragments. A DNA molecular dendrogram was established based on cluster analysis by UPGMA (unweighted pair-group method with arithmetic average), and the relationship of the wild populations were analyzed, and all the wild populations were authenticated. RESULTS: A total of 439 loci with an average of 43.9 loci per primer and 54.9 loci per population were amplified from 8 wild populations by 10 effective primers. In the total 104 amplified bands, 95 were polymorphic, corresponding to 91.35% genetic polymorphism. The genetic distances were 0. 590 to 0. 727, with an average of 0. 686. CONCLUSION: Distinct genetic differences and extensive genetic diversity were presented among the wild populations. RAPD markers were an informative and useful tool for the genetic diversity, evaluation and authentication of wild populations of Dendrobium officinale. Primer S412 could be used to authenticate 8 wild populations completely.