Mosses share fundamental genetic and physiological processes with
vascular plants, although the two lineages diverged early in land-plant evolution. A comparative study between modern representatives of the two lines may give insight into the evolution of mechanisms that contribute to the complexity of modern plants. meaning that an exogenous
DNA sequence can be targeted to a specific genomic position (a technique called
gene targeting) to create
knockout moss. This approach is called
reverse genetics and it is a powerful and sensitive tool to study the function of
genes and, when combined with studies in higher plants such as
Arabidopsis thaliana, can be used to study molecular plant
evolution. The targeted deletion or alteration of moss genes relies on the integration of a short DNA strand at a defined position in the
genome of the host cell. Both ends of this DNA strand are engineered to be identical to this specific
gene locus. The DNA construct is then incubated with moss
protoplasts in the presence of
polyethylene glycol. As mosses are
haploid organisms, the regenerating moss filaments (
protonemata) can be directly assayed for gene targeting within 6 weeks using
PCR methods. The first study using knockout moss appeared in 1998 and functionally identified
ftsZ as a pivotal gene for the division of an
organelle in a
eukaryote. In addition,
P. patens is increasingly used in
biotechnology. Examples are the identification of moss genes with implications for crop improvement or human health and the safe production of complex
biopharmaceuticals in
moss bioreactors. By multiple gene
knockout Physcomitrella plants were engineered that lack plant-specific post-translational protein
glycosylation. These knockout mosses are used to produce complex biopharmaceuticals in a process called
molecular farming. The genome of
P. patens, with about 500
megabase pairs organized into 27 chromosomes, was completely sequenced in 2008.
Physcomitrella ecotypes, mutants, and
transgenics are stored and made freely available to the scientific community by the
International Moss Stock Center (IMSC). The
accession numbers given by the IMSC can be used for publications to ensure safe deposit of newly described moss materials. Spores of
Physcomitrella patens were successfully germinated on Earth, after previously spending 283 days outside of the
International Space Station in 2022. The moss has also been successfully grown in both micro and (artificially) increased gravity conditions. == Lifecycle ==