Flavonoids from Elaeodendron balae root bark

The root bark of Elaeodendron balae afforded ourateacatechin, ouratea-proanthocyanidin A and a new leucoanthocyanidin derivative elaeocyanidin.     

Engineering herbicide resistance in plants by expression of a detoxifying enzyme

Phosphinothricin (PPT) is a potent inhibitor of glutamine synthetase in plants and is used as a non-selective herbicide. The bar gene which confers resistance in Streptomyces hygroscopicus to bialaphos, a tripeptide containing PPT, encodes a phosphinothricin acetyltransferase (PAT) (see accompanying paper). The bar gene was placed under control of the 35S promoter of the cauliflower mosaic virus and transferred to plant cells using Agrobacterium-mediated transformation. PAT was used as a selectable marker in protoplast co-cultivation. The chimeric bar gene was expressed in tobacco, potato and tomato plants. Transgenic plants showed complete resistance towards high doses of the commercial formulations of phosphinothricin and bialaphos. These data present a successful approach to obtain herbicide-resistant plants by detoxification of the herbicide.     

Conservative site-specific and single-copy transgenesis in human LINE-1 elements

Genome engineering of human cells plays an important role in biotechnology and molecular medicine. In particular, insertions of functional multi-transgene cassettes into suitable endogenous sequences will lead to novel applications. Although several tools have been exploited in this context, safety issues such as cytotoxicity, insertional mutagenesis and off-target cleavage together with limitations in cargo size/expression often compromise utility. Phage λ integrase (Int) is a transgenesis tool that mediates conservative site-specific integration of 48 kb DNA into a safe harbor site of the bacterial genome. Here, we show that an Int variant precisely recombines large episomes into a sequence, termed attH4X, found in 1000 human Long INterspersed Elements-1 (LINE-1). We demonstrate single-copy transgenesis through attH4X-targeting in various cell lines including hESCs, with the flexibility of selecting clones according to transgene performance and downstream applications. This is exemplified with pluripotency reporter cassettes and constitutively expressed payloads that remain functional in LINE1-targeted hESCs and differentiated progenies. Furthermore, LINE-1 targeting does not induce DNA damage-response or chromosomal aberrations, and neither global nor localized endogenous gene expression is substantially affected. Hence, this simple transgene addition tool should become particularly useful for applications that require engineering of the human genome with multi-transgenes.     

Desynapsis inColocasia antiquorum Schott.

A culture ofColocasia antiquorum Schott. (2n=28) exhibiting desynapsis was detected in the course of cytological screening of a large number of cultivars maintained at the Institute. Intensive studies on the course of meiosis in this material as well as in the normal plants were made commencing from pachytene stage. Meiosis in the normal plants was regular, leading to the production of 95% stainable pollen. On the other hand, meiosis in the desynaptic material was found to be highly irregular resulting in the formation of over 80% sterile pollen. In its meiotic behaviour, the desynapticColocasia conforms to the complete type of desynaptics. The available evidence suggests a spontaneous origin of the desynaptic through gene mutation. The utility of this material in the study of unravelling basic cytogenetical problems is discussed.     

Cytogenetics of the F1 hybrid between cassava and ceara rubber,and its backcross

Cytogenetical studies of the F₁ hybrid between the commercially cultivated tuber crop, cassava (Manihot esculenta Crantz.) and the closely related wild speciesManihot glaziovii Muell. (Ceara rubber) used as donor specles for Cassava mosaic discase and drought-resistant genes and back crosses (to cassava parent) were made. The contrasting parental characters showed partial to total dominance in the F₁ hybrid, while the back cross plants were similar to cassava in most of their characters. Eleven of the twelve backeross plants exhibited resistance to Cassava mosaic under field conditions. Karyological similarities and differences as resolved on the basis of a comparative study of the karyotypes of the cassava parent and coara rubber were corroborated by the study of chromosomal pairing in the F₁ at pachytene. Major chromosomal differentiation in the two species involved three chromosomes of their haploid complement which were represented by three heteromorphic bivalent associations in F₁ each consisting of a probably basic chromosomal type and a derived type. Pachytene analyses of three back cross plants provided direct proof for random transmission of marker chromosomes of both the parents through male gametes of the F₁ hybrid. An increase in the chiasma frequency in the back cross plants over the F₁ hybrid at metaphase I stage was also observed. Pollen fertility of the backeross plants showed considerable variation.     

SAMase gene of bacteriophage T3 is responsible for overcoming host restriction.

Deletion and point mutants of T3 have been isolated and used to show that the early region of T3 DNA is organized in the same way as that of T7 DNA. Homologous early RNAs and proteins of the two phages have been identified by electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate. Both phages have five early mRNA's, numbered 0.3, 0.7, 1,1.1 and 1.3 from left to right, although no T3 protein that corresponds to the 1.1 protein of T7 has yet been identified. In general, corresponding early RNAs and proteins of the two phages migrate differently on gels, indicating that they differ in molecular weight and/or conformation. In both T7 and T3, gene 0.3 is responsible for overcoming the DNA restriction system of the host, gene 0.7 specifies a protein kinase, gene 1 specifies a phage-specific RNA polymerase, and gene 1.3 specifies a polynucleotide ligase. The 0.3 protein of T3 is responsible for the S-adenosylmethionine cleaving activity (SAMase) induced after T3 (but not T7) infection. However, cleaving of S-adenosylmethionine does not appear to be the primary mechanism by which T3 overcomes host restriction, since at least one mutant of T3 has lost the SAMase activity without losing the ability to overcome host restriction.     

Azoalkyl ether imidazo[2,1-b]benzothiazoles as potentially antimicrobial agents with novel structural skeleton

A series of new azoalkyl ether imidazo[2,1-b]benzothiazoles were developed via a convenient synthetic procedure. The antimicrobial assays showed that a good number of the prepared derivatives exhibited significant inhibitory properties against most of the tested strains. Especially 2-methyl-5-nitroimidazole derivative 5a presented superior inhibit activity against MRSA and B. typhi with MIC?=?4?μg/mL and MIC?=?1?μg/mL, respectively. The highly active compound 5a showed low toxicity against mammalian cells without obvious triggering of the development of bacterial resistance, and it also possessed rapid bactericidal efficacy. Molecular docking study exposed that the active molecule 5a could interact with the active site of S. aureus gyrase through hydrogen bond. Quantum chemical studies were also performed to explain the high antibacterial activity. Further investigation revealed that compound 5a could significantly associate with gyrase–DNA complex by mean of hydrogen bonds and could efficiently intercalate into MRSA DNA to form 5a–DNA supramolecular complex, which impart potent bioactivity.