Lignin genetic engineering

Although lignins play important roles in plants, they often represent an obstacle to the utilization of plant biomass in different areas: pulp industry, forage digestibility. The recent characterization of different lignification genes has stimulated research programmes aimed at modifying the lignin profiles of plants through genetic engineering (antisense and sense suppression of gene expression). The first transgenic plants with a modification of monomeric composition of lignins and lignin content have been recently obtained. Down regulation of the OMT gene induces dramatic reduction of syringyl units. CAD down regulated plants exhibit a unusual red phenotype associated with the developing xylem and several chemical modifications of their lignins including an increase in cinnamaldehydes in the polymer structure. Interestingly this novel lignin is removed more easily during the pulping process. In both OMT and CAD down regulated plants no changes in phenotypic characteristics such as growth architecture and morphology were observed. More recent experiments have shown that a reduction of CCR activity determines specific changes in the coloration of the xylem area suggesting significant chemical modifications which are currently being studied.These different results show that it is possible to manipulate lignins through targeted genetic transformation of plants and that lignins exhibit a relative flexibility of their chemical structure. Future developments should probe the impact of down regulating the expression of other recently characterized lignification genes such as F5H and CCoAOMT and also of a combination of genes in order to tailor lignins more adapted to specific purposes. In addition to biotechnological applications which should provide important economical benefits for utilization of wood in the pulp industry, genetic engineering of lignins offer very promising perspectives for the understanding of lignin synthesis, structure and properties.     

100 years of virology: from vitalism via molecular biology to genetic engineering

The identification of the causative agent of tobacco mosaic disease as a novel pathogen by the Dutch microbiologist Beijerinck is now acknowledged as being the foundation of virology as a discipline distinct from bacteriology. However, as this was contrary to the prevailing theories of the time, it took many years for virology to become firmly established as a separate discipline. The history of virology illustrates how accepted concepts in science evolve by trial and error and the need for a balanced approach when manipulating natural systems.     

Journalists and genetic engineering

Mass media coverage of genetic engineering is considered as an essential cause of the public image which this technology has. Because most people have only few experiences with this technology, the influence of journalists, who report on genetic engineering, seems to be obviously high. Which attitudes do these journalists have? How do they inform themselves? These and other questions are to be answered by a standardized survey among German journalists. For the first time the results of this study reveal the methods of investigation and source selection of 'genetic engineering journalists' and afford an insight into the journalistic climate of opinion on genetic engineering and its applications. There is clear evidence of an altogether positive global judgement of journalists reporting on this technology, which finds support in their immediate professional social environment.     

Effect of Bt genetic engineering on indirect defense in cotton via a tritrophic interaction

We present a tritrophic analysis of the potential non-intended pleiotropic effects of cry1Ac gene derived from Bacillus thurigiensis (Bt) insertion in cotton (DeltaPine 404 Bt Bollgard® variety) on the emission of herbivore induced volatile compounds and on the attraction of the egg parasitoid Trichogramma pretisoum (Hymenoptera: Trichogrammatidae). Both the herbivore damaged Bt variety and its non-Bt isoline (DeltaPine DP4049 variety) produced volatiles in higher quantity when compared to undamaged plants and significantly attracted the egg parasitoids (T. pretiosum) when compared to undamaged plants. However, Trichogramma pretiosum did not differentiate between the transgenic and nontransgenic varieties, suggesting that the ratios between the compounds released by herbivory damaged -Bt cotton and herbivory damaged-nonBt cotton did not change significantly. Finally, no detrimental effect of the Bt genetic engineering was detected related to the volatile compounds released by Bollgard cotton on the behavior of the natural enemy studied.     

Plastid genetic engineering in Solanaceae

Plastid genetic engineering has come of age, becoming today an attractive alternative approach for the expression of foreign genes, as it offers several advantages over nuclear transformants. Significant progress has been made in plastid genetic engineering in tobacco and other Solanaceae plants, through the use of improved regeneration procedures and transformation vectors with efficient promoters and untranslated regions. Many genes encoding for industrially important proteins and vaccines, as well as genes conferring important agronomic traits, have been stably integrated and expressed in the plastid genome. Despite these advances, it remains a challenge to achieve marked levels of plastid transgene expression in non-green tissues. In this review, we summarize the basic requirements of plastid genetic engineering and discuss the current status, limitations, and the potential of plastid transformation for expanding future studies relating to Solanaceae plants.     

Actinomycetes--the test-organisms of genetic engineering

The paper contains a short review of the data on using the methods of genetic engineering in studies of genetics and molecular biology in Streptomyces. The techniques of DNA introduction into actinomycetes and wide-spread vectors are briefly described. The origin of the actinomycete plasmids as chromosomal segments capable of autonomous replication is discussed. In this view, it is suggested that genetic instability in actinomycetes is connected with excision of specific DNA sequences from the chromosome at frequencies characteristic of recombination events. Also, amplification of short DNA segments within the chromosome resulting in tandem repeats is a consequence of unequal crossing over between direct repeats flanking the amplifying DNA and, possibly, of induction of replication of this DNA. The data on molecular cloning of actinomycete genes for primary metabolism and those for resistance to and biosynthesis of antibiotics, on using actinomycetes as the hosts for foreign genes to be expressed, as well as on analysis of nucleotide sequences of actinomycete DNA, are presented.     

Natural genetic engineering in evolution

The results of molecular genetics have frequently been difficult to explain by conventional evolutionary theory. New findings about the genetic conservation of protein structure and function across very broad taxonomic boundaries, the mosaic structure of genomes and genetic loci, and the molecular mechanisms of genetic change all point to a view of evolution as involving the rearrangement of basic genetic motifs. A more detailed examination of how living cells restructure their genomes reveals a wide variety of sophisticated biochemical systems responsive to elaborate regulatory networks. In some cases, we know that cells are able to accomplish extensive genome reorganization within one or a few cell generations. The emergence of bacterial antibiotic resistance is a contemporary example of evolutionary change; molecular analysis of this phenomenon has shown that it occurs by the addition and rearrangement of resistance determinants and genetic mobility systems rather than by gradual modification of pre-existing cellular genomes. In addition, bacteria and other organisms have intricate repair systems to prevent genetic change by sporadic physicochemical damage or errors of the replication machinery. In their ensemble, these results show that living cells have (and use) the biochemical apparatus to evolve by a genetic engineering process. Future research will reveal how well the regulatory systems integrate genomic change into basic life processes during evolution.     

Redesigning the NEDD8 pathway with a bacterial genetic screen for ubiquitin-like molecule transfer

Pathways of ubiquitin-like (UBL) molecule transfer regulate a myriad of cellular cascades. Here, we report a high-throughput assay that correlates catalytic human NEDD8 transfer to bacterial survival. The assay was utilized to screen mutant NEDD8 and NAE (NEDD8-activating enzyme) libraries to engineer a more stable NEDD8 and redesign the NEDD8-NAE interface. This approach will be useful in understanding the specificities underlying UBL pathways.