Physcomitrella patens

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Physcomitrella patens
Scientific classification Edit this classification
Kingdom: Plantae
Division: Bryophyta
Class: Bryopsida
Subclass: Funariidae
Order: Funariales
Family: Funariaceae
Genus: Physcomitrella
Species:
P. patens
Binomial name
Physcomitrella patens
Synonyms [1]
  • 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 is a synonym of Physcomitrium patens,[2][3] the spreading earthmoss.[4] It is a moss, a bryophyte used as a model organism for studies on plant evolution, development, and physiology.[3]

Distribution and ecology

Physcomitrella patens is an early colonist of exposed mud and earth around the edges of pools of water.

Gransden Wood, in Cambridgeshire in 1962.[5]

Model organism

See also: Knockout moss

Mosses share fundamental genetic and physiological processes with

vascular plants, although the two lineages diverged early in land-plant evolution.[8] 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.[8] In this context, P. patens is used as a model organism.[8][3]

P. patens is one of a few known

genes and, when combined with studies in higher plants such as Arabidopsis thaliana, can be used to study molecular plant evolution.[citation needed
]

The targeted deletion or alteration of moss genes relies on the integration of a short DNA strand at a defined position in the

protonemata) can be directly assayed for gene targeting within 6 weeks using PCR methods.[11] 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.[12]

In addition, P. patens is increasingly used in

molecular farming.[15]

The genome of P. patens, with about 500

megabase pairs organized into 27 chromosomes, was completely sequenced in 2008.[8][16]

Physcomitrella

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.[citation needed
]

Lifecycle

Like all mosses, the lifecycle of P. patens is characterized by an alternation of two generations: a

spores are produced.[17]

A spore develops into a filamentous structure called

monoicous, meaning that male and female organs are produced in the same plant. If water is available, flagellate sperm cells can swim from the antheridia to an archegonium and fertilize the egg within. The resulting diploid zygote develops into a sporophyte composed of a foot, seta, and capsule, where thousands of haploid spores are produced by meiosis.[19]

DNA repair and homologous recombination

P. patens is an excellent model in which to analyze repair of DNA damages in plants by the homologous recombination pathway. Failure to repair double-strand breaks and other DNA damages in somatic cells by homologous recombination can lead to cell dysfunction or death, and when failure occurs during meiosis, it can cause loss of gametes. The genome sequence of P. patens has revealed the presence of numerous genes that encode proteins necessary for repair of DNA damages by homologous recombination and by other pathways.[8] PpRAD51, a protein at the core of the homologous recombination repair reaction, is required to preserve genome integrity in P. patens.[20] Loss of PpRAD51 causes marked hypersensitivity to the double-strand break-inducing agent bleomycin, indicating that homologous recombination is used for repair of somatic cell DNA damages.[20] PpRAD51 is also essential for resistance to ionizing radiation.[21]

The DNA mismatch repair protein PpMSH2 is a central component of the P. patens mismatch repair pathway that targets base pair mismatches arising during homologous recombination. The PpMsh2 gene is necessary in P. patens to preserve genome integrity.[22] Genes Ppmre11 and Pprad50 of P. patens encode components of the MRN complex, the principal sensor of DNA double-strand breaks.[23] These genes are necessary for accurate homologous recombinational repair of DNA damages in P. patens. Mutant plants defective in either Ppmre11 or Pprad50 exhibit severely restricted growth and development (possibly reflecting accelerated senescence), and enhanced sensitivity to UV-B and bleomycin-induced DNA damage compared to wild-type plants.[23]

  • Cleistocarpous sporophyte of the moss P. patens
    Cleistocarpous sporophyte of the moss P. patens
  • P. patens plants growing axenically in vitro on agar plates (Petri dish, 9 cm diameter)
    P. patens plants growing axenically in vitro on agar plates (Petri dish, 9 cm diameter)
  • Moss bioreactor with P. patens
    Moss bioreactor with P. patens
  • Four different ecotypes of P. patens stored at the International Moss Stock Center
    Four different ecotypes of P. patens stored at the International Moss Stock Center
  • Protonema cells of P. patens
    Protonema cells of P. patens
  • The polycomb gene FIE is expressed (blue) in unfertilised egg cells of the moss P. patens (right) and expression ceases after fertilisation in the developing diploid sporophyte (left). In situ GUS staining of two female sex organs (archegonia) of a transgenic plant expressing a translational fusion of FIE-uidA under control of the native FIE promoter.[24]
    The polycomb gene FIE is expressed (blue) in unfertilised egg cells of the moss P. patens (right) and expression ceases after fertilisation in the developing diploid sporophyte (left). In situ GUS staining of two female sex organs (archegonia) of a transgenic plant expressing a translational fusion of FIE-uidA under control of the native FIE promoter.[24]
  • Physcomitrella knockout mutants: Deviating phenotypes induced by transformation with a gene-disruption-library. Physcomitrella wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of gametophores. For each plant, an overview (upper row; scale bar corresponds to 1 mm) and a close-up (bottom row; scale bar equals 0.5 mm) are shown. A: Haploid wild-type moss plant completely covered with leafy gametophores and close-up of wild-type leaf. B–E: Different mutants.[25]
    Physcomitrella knockout mutants: Deviating phenotypes induced by transformation with a gene-disruption-library. Physcomitrella wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of gametophores. For each plant, an overview (upper row; scale bar corresponds to 1 mm) and a close-up (bottom row; scale bar equals 0.5 mm) are shown. A: Haploid wild-type moss plant completely covered with leafy gametophores and close-up of wild-type leaf. B–E: Different mutants.[25]

Taxonomy

P. patens was first described by Johann Hedwig in his 1801 work Species Muscorum Frondosorum, under the name Phascum patens.[1] Physcomitrella is sometimes treated as a synonym of the genus Aphanorrhegma, in which case P. patens is known as Aphanorrhegma patens.[26] The generic name Physcomitrella implies a resemblance to Physcomitrium, which is named for its large calyptra, unlike that of Physcomitrella.[18] In 2019 it was proposed that the correct name for this moss is Physcomitrium patens.[2][3]

References

  1. ^ a b "!Physcomitrella patens (Hedw.) Bruch & Schimp". Tropicos. Missouri Botanical Garden. Retrieved October 28, 2012.
  2. ^
    ISSN 1759-6831
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  3. ^
    PMC 7203925
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  4. ISSN 0268-8034
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  5. ^ a b Andrew Cuming (2011). "Molecular bryology: mosses in the genomic era" (PDF). Field Bryology. 103: 9–13.
  6. ISBN 978-0-9561310-1-0
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  7. ISBN 9781444316070. In: Knight et al. (2009)
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  8. ^
    S2CID 11115152
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  9. PMID 9225463
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  10. PMID 12221986
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  11. S2CID 45780217
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  12. PMID 9539743
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  13. PMID 15975264
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  14. PMID 17869503
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  15. PMID 17147624
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  16. S2CID 36669399.{{cite journal}}: CS1 maint: multiple names: authors list (link
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  17. doi:10.1016/j.cub.2023.09.042
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  18. ^ a b Bernard Goffinet (2005). "Physcomitrella". Bryophyte Flora of North America, Provisional Publication. Missouri Botanical Garden. Retrieved October 28, 2012.
  19. doi:10.1080/07352689.2018.1482396
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  20. ^
    PMID 17921313
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  21. PMID 20189889
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  22. PMID 16397301
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    PMID 22210882
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  24. S2CID 1757579
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  25. PMID 12123528
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  26. ISBN 9781444316070. In: Knight et al. (2009)
    .

Further reading

External links

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