Using RAPD Method on Systematic Evolution of Four Species in Anura

The phylogenetic relationships of four species,Bufo melanostictus,Hyla chinensis,Rana limnocharis and Rana guentheri,which belong to three differrent families of Anura,were detected with RAPD technique.The genomic DNA of each species was amplified with 19 random primers.16 primers given clear amplified bands were used for analysis and the genetic distances between four species were calculated.The results show that RAPD bands obtained by all 16 primers evinced different degree polymorphisms.The genetic distance between R.limnocharis and R.guentheri is the nearest,that between B.melanostictus and H.chinensis is the second nearest,and that between B.melanostictus and R.guentheri is the furthest.The different distances also indicated that the relationship between Bufoidae and Hylidae is closer than that between Bufonidae and Ranidae at genomic DNA level.In concordant with the conclusion of the morphology,chromosomal and mitochondrial DNA studies,our results provide a new evidence of the systematic evolution of the three families of Anura at DNA molecular level.

Molecular Systematic Studies on Chinese Mandarina Silkworm (Bombyx mandarina M.) and Domestic Silkworm (Bombyx mori L.)

Molecular systematic studies on mandarina silkworm (Bombyx mandarina M.) in 11 regions in China and 25 representative strains of domestic silkworm (Bombyx mori L.) were conducted using molecular biology techniques. Results obtained from the analysis of DNA polymorphism and clustering of all the silkworm samples provide new evidence for the view that the domestic silkworm originated from the Chinese mandarina silkworm. On the basis of literature reviewing, a new hypothesis on the origin of the domestic silkworm was put forward. It was thought that the domestic silkworm was most probably domesticated from the Chinese mandarina silkworm of different ecotypes including monovoltinism, bivoltinism and multivoltinism; and that the domestic silkworm had the genetic background of monovoltinism, bivoltinism and multivoltinism at the very beginning of the domestication. The current strains of the domestic silkworm of different voltinism are the evolutionary results of thousands of years of rearing and artificial selections.

Human Resource Ecosystem and its evolutionary rules

The paper, based on the concept and the elements of human resource ecosystem (HR Ecosystem), studies the function and structure of HR Ecosystem, introduces the entropy theory to define the content of entropy of HR Ecosystem, constructs the corresponding distinctive model to distinguish the direction of the evolution of HR Ecosystem and the evolutionary entropy model, and applies the models to demonstrate the evolutionary rules of HR Ecosystem. The study shows that the entropy theory can be well applied to the analysis on HR Ecosystem and that it opens up a new field in the research of human resource management and provides a new effective technical method.

New Schizolepis Fossils from the Early Cretaceous in Inner Mongolia, China and its Phylogenetic Position

Three Schizolepis species collected from the Lower Cretaceous layer of the Huolinhe Basin, Inner Mongolia, China are described. These fossils are Schizolepis longipetiolus Xu XH et Sun BN sp. nov., which is a new species, Schizolepis cf. heilongjiangensis Zheng et Zhang, and Schizolepis neimengensis Deng. The new species is a well-preserved female cone, slender and cylindrical in shape. The seed-scale complexes have long petioles and are arranged on the cone axis loosely and helically. The seed scales are divided into two lobes from the base. Each lobe is semicircular or elongate ligulate in shape, widest at the middle or the lower middle part, with an obtuse or bluntly pointed apex. The inner margin is almost straight and the outer margin is strongly arched. On the surface of the lobe, there are longitudinal and somewhat radial striations from the base to the margin. The seed is borne on the adaxial surface at the base or middle of each lobe. Schizolepis was estabfished in 1847, and, although more than twenty species have been discovered and reported, its phylogenetic position is controversial because of the imperfection of fossils. Most authors have considered there to be a close evolutionary relationship between Schizolepis and extant Pinaceae. Here, we analyze characteristics and compare Schizolepis with Picea crassifolia Kom, which is morphologically most similar to Schizolepis. The results indicate that the genus probably has a distant evolutionary relationship with extant Pinaceae. A detailed statistical analysis of the global paleogeographic distribution of Schizolepis showed that all the fossils of this genus appeared in strata ranging from the Upper Triassic to the Lower Cretaceous in the North Hemisphere, being rare in the Upper Triassic and Lower Jurassic, but being very common from the Middle Jurassic to the Lower Cretaceous, and particularly abundant in the Lower Cretaceous. According to the statistical results, we speculate that the genus originated in Europe in the Late Triassic then spread from Europe to Asia between the Late Triassic and the Late Jurassic. In the Early Cretaceous most species existed in China＇s three northeastern Provinces and the Inner Mongolia Autonomous Region and adjacent areas. Combining the paleogeographic distribution of the genus with ancient climatic factors, we deduced that Schizolepis began to decline and became extinct in the Early Cretaceous, and the reason for its extinction is closely related to the icehouse climate during the Early Cretaceous.

Development of HBsAg-Binding Aptamers that bind HepG2.2.15 cells via HBV surface antigen

Hepatitis B virus surface antigen （HBsAg）, a specific antigen on the membrane of Hepatitis B virus （HBV）-infected cells, provides a perfect target for therapeutic drugs. The development of reagents with high affinity and specificity to the HBsAg is of great significance to the early-stage diagnosis and treatment of HBV infection. Herein, we report the selection of RNA aptamers that can specifically bind to HBsAg protein and HBsAg-positive hepatocytes. One high affinity aptamer, HBs-A22, was isolated from an initial 115 met library of -1.1 ×10^15 random-sequence RNA molecules using the SELEX procedure. The selected aptamer HBs-A22 bound specifically to hepatoma cell line HepG2.2.15 that expresses HBsAg but did not bind to HBsAg-devoid HepG2 cells. This is the first reported RNA aptamer which could bind to a HBV specific antigen. This newly isolated aptamer could be modified to deliver imaging, diagnostic, and therapeutic agents targeted at HBV-infected cells.

In vitro Selection of DNA Aptamers and Fluorescence-Based Recognition for Rapid Detection Listeria monocytogenes

Aptamers are specific nucleic acid sequences that can bind to a wide range of nucleic acid and non-nucleic acid targets with high affinity and specificity. Nucleic acid aptamers are selected in vitro from single stranded DNA or RNA ligands containing random sequences of up to a few hundred nucleotides. Systematic evolution of ligands by exponential enrichment （SELEX） was used to select and PCR amplify DNA sequences （aptamers） capable of binding to and detecting Listeria monocytogenes, one of the major food-borne pathogens. A simplified affinity separation approach was employed, in which L. monocytogenes in exponential （log） phase of growth was used as the separation target. A fluorescently-labeled aptamer assay scheme was devised for detecting L. monoeytogenes. This report described a novel approach to the detection of L. monocytogenes using DNA aptamers. Aptamers were developed by nine rounds of SELEX. A high affinity aptamer was successfully selected from the initial random DNA pool, and its secondary structure was also investigated. One of aptamers named e01 with the highest affinity was further tested in aptamer-peroxidase and aptamer-fluorescence staining protocols. This study has proved the principle that the whole-cell SELEX could be a promising technique to design aptamer-based molecular probes for dectection of pathogenic microorganisms without tedious isolation and purification of complex markers or targets.

A New Species of Ginkgo with Male Cones and Pollen Grains in situ from the Middle Jurassic of Eastern Xinjiang,China

Well-preserved Ginkgo pollen organs are analyzed from the Middle Jurassic Xishanyao Formation of the Turpan–Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China, and are described as a new species, Ginkgo hamiensis Z.X. Wang et B.N. Sun sp. nov. The immature male cones are cylindrical and catkin-like, with two longitudinal stripes on the stalk. The pollen sacs are shaped like a long oval with two pollen sacs fused together for each microsporophyll, and the microsporophyll tip is a triangular cystidium. The pollen grains are oblong or fusiform and monocolpate; both ends are blunt or sharp. By comparison with previously reported fossil records of Ginkgo plants, we determined that the current fossils are different from all other reported species; thus, the present fossil is referred to as a new species of Ginkgo. The reproductive organs of the Ginkgo fossils described herein can provide valuable information for the study of Ginkgo plants. Further, there are two probable evolutionary trends in the Ginkgo pollen cones. One trend is that the number of pollen sacs changed from three or four during the Jurassic and Cretaceous to two at the present day; the other is that the number of pollen sacs has remained two from the Middle Jurassic to the present day. In addition, the pollen cones described herein are similar to the pollen cones of the extant Ginkgo, which strongly indicates that the morphology of Ginkgo plants may have remained highly conserved over millions of years.

An Aptamer-based Colorimetric Sensor for Streptomycin and Its Application in Food Inspection

An aptamer-based colorimetric biosensor was developed, which could be used to detect residual strepto- mycin from food quickly and cost-effectively. The ssDNA aptamer target for streptomycin was obtained using sys- temic evolution of ligands by exponential enrichment through affinity chromatography. A total of 19 candidates were obtained after 10 rounds of selection and were grouped into 3 families according to their similarity of sequence and structure. Among them, aptamer A15 showed the highest affinity for streptomycin tested by fluorescence intensity analysis with a dissociation constant of 6.07 nmol/L. Aptamer A15 also exhibited a higher streptomycin specificity with the lowest detectable limit of 25 nmol/L according to the value of A620/A520 ratio with AuNP-based colorimetric assay. The method was specific and sensitive for the detection of streptomycin from simply-treated milk and honey at 100 and 125 nmol/L, respectively, and is a promising approach to monitor antibiotics or other small molecules ana- logues in food inspection.

Progress in DNA Aptamers as Recognition Components for Protein Functional Regulation

Proteins play a central role in all domains of life,and precise regulation of their activity is essential for understanding the related biological processes and therapeutic functions.Nucleic acid aptamers,the molecular recognition components derived from systematic evolution of ligands by exponential enrichment(SELEX),can specifically identify proteins with antibody-like recognition characteristics and help to regulate their activity.This minireview covers the SELEX-based selection of protein-binding aptamers,membrane protein analytical techniques based on aptamer-mediated target recognition,aptamer-mediated functional regulation of proteins,including membrane receptors and non-membrane proteins(thrombin as a model),as well as the potential challenges and prospects regarding aptamer-mediated protein manipulation,aiming to supply some useful information for researchers in this field.