Moss – An Innovative Tool for Protein Production

The complete sequencing of the human genome has significantly increased the number of pharmaceutically important proteins (“biopharmaceuticals”) to be produced at large scale. As this tendency is expected to continue, production capacity of biopharmaceuticals has become a strategic issue for the pharmaceutical industry. Mammalian cells such as those of baby hamster kidney and Chinese hamster ovary have been used for more than two decades. However, these systems require major investments in production facilities and running costs of production are very high. Among other technologies, e. g. yeasts and transgenic animals, plants are an alternative for the production of recombinant proteins [1]. So far seed plants like tobacco, corn, and Alfalfa, have been tested for molecular farming. We here will focus on a moss, Physcomitrella patens, as an innovative tool. Physcomitrella has a moderately small genome of 511 Mbp [2]. Mosses are higher multicellular eukaryotes and therefore perform extensive posttranslational processing of proteins including the formation of disulfide bridges and complex glycosylation. Their major developmental stage is the haploid gametophyte (Fig. 1). In contrast, the dominating developmental stage of seed plants is the diploid or polyploid sporophyte [3]. Moss is unique among all multicellular plants analyzed to date in exhibiting a very effective homologous recombination in its nuclear DNA. This allows targeted knockouts of genes [4, 5], which is a highly attractive tool for production strain design. Thus, the manipulation of the glycosylation pathway is Fig. 1: The moss Physcomitrella patens