Fluorescence Tracking of Exogenous DNA in Genetic Transformation of the Chinese Oak Silkmoth Antheraea Pernyi via Sperm-Mediated Gene Transfer

Exogenous DNA expressing green fluorescent protein( GFP) and labeled with fluorescein isothiocyanate( FITC) was used to transform the Chinese oak silkmoth Antheraea pernyi( A. pernyi)via sperm-mediated gene transfer( SMGT). Sperms entry into the female reproductive system and eggs were observed using fluorescence microscopy. The ability of A. pernyi sperms to uptake exogenous DNA was confirmed,and transfer of the exogenous DNA was shown by GFP expression in the transgenic eggs. Our result suggested that SMGT could also be used to directly generate transgenic A. pernyi expressing functional genes of interest.

Restriction of exogenous DNA expression by SAMHD1

SAMHD1(Sterile Alpha Motif and Histidine-aspartate Domain containing protein 1) has been documented as a host factor that restricts HIV-1 and some DNA viruses. In this work, we attempted to explore possible effects of SAMHD1 on exogenous DNA and show that SAMHD1 exerts a general inhibition on the expression of exogenous DNA in vitro and in mice. This inhibition is achieved through repressing transcription of exogenous DNA. Intriguingly, unlike SAMHD1’s restriction of HIV-1, such restriction does not require the dNTPase or RNase activities, or T592 phosphorylation of SAMHD1. Mechanistically,SAMHD1 enhances the expression of interferon regulatory factor-1(IRF1), while IRF1 upregulation was demonstrated to inhibit exogenous DNA expression in a similar fashion as SAMHD1. IFNk1, whose induction has been associated with IRF1 activation, is dispensable for SAMHD1/IRF1-mediated restriction of exogenous DNA, and neither type Ⅰ nor Ⅱ interferons appear to be involved. We also demonstrate that SAMHD1/IRF1-mediated restriction can effectively inhibit hepatitis B virus(HBV) antigen expression and progeny virus production in mouse models. In conclusion, these data support restriction of exogenous DNA as a novel function of SAMHD1.

Transgenic Crops by Direct Treatment of Exogenous DNA without Agrobacterium tumefaciens Plasmid and Tissue Culture

Gene transfer methods are developing quickly recently, but each method has its limitations. We introduce a new gene transfer technique in this paper, which is simple, effective, and easy to operate,but does not get enough attention from scientists. This technique is used to transform plants by in jecting exogenous DNA to stigma, style, ovary, young fruit or meristem of the recipient, or soaking the recipient's seeds in exogenous DNA solution. Lots of heritable variations were found in many characters of many crops. It may be used to create new germplasms or realize gene exchange between different species, genera, or families, even between animals and plants. A brief discussion was given to the mechanism of exogenous DNA introduction, integration into and expression in the recipient. We also discussed the merits and limitations of the technique.Currently there are two successful approaches that can be used to transform paints genetically,but each method has its limitations that are delaying the application of the techniques to certain commercially important crops. The first technique exploits a natural genetic engineer, Agrobacterium tumefaciens, which contains a tumor-inducing (Ti) plasmid that transfers a DNA segment (the T-DNA) from the plasmid to the nuclear genome of infected plants (or in vitro to plant tissue). The method is restricted to dicotyledenous plants; monocotyledenous plants are usually not susceptible to agrobacterial infection. The second technique involves direct transfer of DNA to plant protoplast, prepared by enzymatic digestion of cell walls, for example by chemically stimulated uptake using polyethylene glycol or a high voltage pulse, generating transient 'holes' in the protoplast membrane. This technique depends on a tissue culture system that allows regeneration of mature plants from protoplasts. But so far it is impossible to achieve plant regeneration from protoplasts in many crops. Both techniques use dominant selectable markers (for example, kanamycin resistance) to select for the transformed tissue or plant which can then be screened for expression of co-transferred but unselected genes (Lichenstein, 1987).Now there is a new successful method which can transform various crops, regardless of dicots or monocots, cereals or legumes. It doesn't need Agrobacterium tumefaciens and plasmid, doesn't depend on the tissue culture system that allows regeneration of mature plants from protoplasts.Comple and advance equipments are not necessary. It is very simple, but very effective. Next is a review about the technique, its application in several crops, the mechanism of transformation, and its merits and limitations.

Urinary Tract Infection Escherichia coli Is Related to the Environmental Escherichia coli in Their DNA Barcoding and Antibiotic Resistance Patterns in Grenada

Urinary Tract Infections (UTIs) are among one of the most common infections in women, with uropathogenic E. coli (UPEC) being involved in 80% of cases. In addition, E. coli exhibits an increasing resistance to broad spectrum antimicrobial agents as well as the subsequent generations of these drugs. The genetic diversity and antibiotic resistance patterns of both clinical and environmental E. coli isolates were studied to predict the potential of transmission of organisms and genes for antibiotic resistance from three different major eco-habitats including the gut of iguanas’ fresh and marine waters and the human urinary tract. (GTG)5 and BOX-PCR extragenic DNA fingerprinting allowed for the tracking of the relatedness of four different ecotype groups. Both DNA fingerprinting methods targeted non-protein coding or exogenous palindromic DNA and demonstrated shared origin and intraspecies level of genomic diversity within the population of the studied bacteria. DNA fingerprinting based on BOX-PCR was less discriminating than the (GTG)5-PCR, and produced five major clades. BOX-PCR analysis indicated that 44% of the UTI E. coli isolates was comprised within a single clade, therefore it correlated better with ecotype distribution. The (GTG)5 PCR based co-clustering analysis showed that the clinical isolates appeared to have a closer relationship to iguana E. coli isolates than to the fresh and marine water isolates. However, in accordance with the BOX PCR co-clustering analysis, the clinical isolates were most similar to the marine water isolates, followed by the freshwater and iguana E. coli isolates. Seventy two percent of antibiotic resistance patterns were shared by the UTI strains with E. coli isolated from freshwater, followed by iguana.