Barbara Hohn

The basis of my career as molecular biologist was laid by work on bacteriophages fd (in Tuebingen and Yale) and lambda (Biocenter, Basel). The studies of morphogenesis of lambda led to in vitro assembly and DNA packaging of this beautiful model virus. This was early times of recombinant DNA and the possibility to make recombinant lambda DNA infectious by packaging it into its preformed capsid was most welcome. As an extension of this work hybrid plasmids containing the phage packaging site cos, later called cosmids were developed. These allowed the cloning of large fragments of DNA and libraries of genomic DNA of many organisms were produced all over the world. However, the most interesting aspect is that of unintended, serendipitous findings applicable for unforeseen uses.

With the move from the Biocenter to the FMI came the move to eukaryotic organisms, specifically plants. In collaboration with plant scientists already located at the FMI studies on transformation of and genetic recombination in plants were conducted. Especially intriguing thereby was to get to know the prokaryotic organism Agrobacterium tumefaciens which has been shown a long time ago to be able to genetically transform (some) plants. The study of the mechanism of transfer of DNA to plants was a fascinating lesson. Again, the naïve and curiosity-driven search for basic principles led to the discovery of the agronomically important grasses such as maize as unforeseen hosts for the bacterium's DNA transfer.

Genomes change over time; an interesting and partially essential contribution to this change is homologous recombination, active as DNA repair pathway in somatic tissue and of critical importance for rearrangement of genes during meiosis. With the help of specially designed marker genes in the transformed model plant Arabidopsis thaliana somatic recombination events could be monitored. These plants allowed the isolation of mutant plants changed in one or the other aspect of the recombination pathway. Especially fascinating was the finding that not only agents acting directly on the DNA but also other environmentally important influences such as pathogen attack led to increases in homologous recombination. Could this be part of evolutionary drive? In a step further, plants treated with UV or a molecule imitating a pathogen provided their untreated progeny with a molecularly undefined, but certainly epigenetically based kind of "memory" of their experience; progeny of treated plants exhibited a higher level of homologous recombination than progeny of untreated plants.

I have been especially privileged to witness big steps in the understanding of the molecular basis of life such as cloning of DNA and later transformation of lower and higher eukaryotic organisms including plants. I am equally privileged for having been able to contribute.

Presently I am enjoying a multifaceted life. I am trying, using collaborations, to further explore the nature of the epigenetic changes mentioned above. I am trying to return the work others have done before to guarantee the infrastructure and quality of scientific institutions (Advisory Boards), to help in evaluations of granting agencies and scientific journals. In addition, I am a consultant of European and international networks. These, as well as the intellectually challenging scientific spirit of the FMI, the unbroken chain of invitations to interesting meetings and other activities keep me very busy.
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