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Physcomitrella patens

Physcomitrella patens
Physcomitrella.jpg
Scientific classification
Kingdom: Plantae
Division: Bryophyta
Class: Bryopsida
Order: Funariales
Family: Funariaceae
Genus: Physcomitrella
Species: P. patens
Binomial name
Physcomitrella patens
(Hedw.) Bruch & Schimp.
Synonyms 
  • Phascum patens Hedw.
  • Aphanorrhegma patens (Hedw.) Lindb.
  • Ephemerum patens (Hedw.) Hampe
  • Genthia patens (Hedw.) Bayrh.
  • Physcomitrium patens (Hedw.) Mitt.
  • Stanekia patens (Hedw.) Opiz

Physcomitrella patens, the spreading earthmoss, is a moss (bryophyte) used as a model organism for studies on plant evolution, development, and physiology.

Physcomitrella patens is an early colonist of exposed mud and earth around the edges of pools of water.P. patens has a disjunct distribution in temperate parts of the world, with the exception of South America. The standard laboratory strain is the "Gransden" isolate, collected by H. Whitehouse from Gransden Wood, in Cambridgeshire.

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 can give an insight into the evolution of the mechanisms behind the complexity of modern plants. In this context, P. patens is used as a model organism.

P. patens is one of a few known multicellular organisms with highly efficient homologous recombination. meaning that an exogenous DNA sequence can be targeted to a specific genomic position (a technique called gene targeting) to create knockout mosses. 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.


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