Arabidopsis thaliana (Thale Cress): Difference between revisions

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{{taxobox
{{subpages}}
{{Taxobox
| color = lightgreen
|name = ''Arabidopsis thaliana''
|name = ''Arabidopsis thaliana''
|image = Arabidopsis thaliana.jpg
|image = Arabidopsis thaliana wild type 25 days old.jpg
|regnum = [[Plantae]]
|regnum = [[Plantae]]
|unranked_divisio = [[Angiosperms]]
|unranked_divisio = [[Angiosperms]]
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|binomial = ''Arabidopsis thaliana''
|binomial = ''Arabidopsis thaliana''
|binomial_authority = ([[Carolus Linnaeus|L.]]) Heynh.
|binomial_authority = ([[Carolus Linnaeus|L.]]) Heynh.
|range_map = Arabidopsis thaliana distribution.png
|range_map =  
|synonyms = ''Arabis thaliana''
|synonyms = ''Arabis thaliana''
|}}
|}}
 
'''''Arabidopsis thaliana''''' is a small flowering plant widely used by plant biologists as a [[model species|model organism]] for basic research. It has several common names including '''thale cress''', '''mouse-ear cress''' or just '''Arabidopsis''').<ref name=grin>Germplasm Resources Information Network: [http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?3769 ''Arabidopsis thaliana'']</ref> It is popular for research since it has a relatively short life cycle and its [[genome]] is one of the smaller ones. Due to its prominence in research it was the first plant genome to be sequenced.<ref name="Genome">{{cite journal| author=The Arabidopsis Genome Initiative| title=Analysis of the genome sequence of the flowering plant Arabidopsis thaliana| journal=Nature| year=2000| volume=408| pages=796–815| doi=10.1038/35048692 | pmid=11130711}}</ref>
'''''Arabidopsis thaliana''''' (''[[Syllable stress of Botanical Latin|A-ra-bi-dóp-sis tha-li-á-na]]''; '''thale cress''', '''mouse-ear cress''' or '''Arabidopsis'''), is a small [[flowering plant]] native to [[Europe]], [[Asia]], and northwestern [[Africa]].<ref name=grin>Germplasm Resources Information Network: [http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?3769 ''Arabidopsis thaliana'']</ref> A spring annual with a relatively short life cycle, Arabidopsis is popular as a [[model organism]] in plant biology and genetics. Its [[genome]] is one of the smallest plant genomes and was the first plant genome to be sequenced. Arabidopsis is a popular tool for understanding the [[molecular biology]] of many plant traits, including [[flower]] development and [[phototropism|light sensing]].


==Habitat, morphology, and life cycle==
==Habitat, morphology, and life cycle==


Arabidopsis is native to [[Europe]], [[Asia]], and northwestern [[Africa]].  It is an [[annual plant|annual]] (rarely [[biennial plant|biennial]]) plant usually growing to 20–25 cm tall. The [[leaf|leaves]] form a rosette at the base of the plant, with a few leaves also on the flowering stem. The basal leaves are green to slightly purplish in colour, 1.5–5 cm long and 2–10 mm broad, with an entire to coarsely serrated margin; the stem leaves are smaller, unstalked, usually with an entire margin. Leaves are covered with small unicellular hairs (called [[trichome]]s). The [[flower]]s are 3 mm in diameter, arranged in a [[Inflorescence#Simple_inflorescences|corymb]]; their structure is that of the typical [[Brassicaceae|Brassicacaea]]. The [[fruit]] is a [[Siliqua (plant)|siliqua]] 5–20 mm long, containing 20–30 [[seed]]s.<ref name=fnwe>Flora of NW Europe: [http://ip30.eti.uva.nl/BIS/flora.php?selected=beschrijving&menuentry=soorten&id=2273 ''Arabidopsis thaliana'']</ref><ref name=blamey>Blamey, M. & Grey-Wilson, C. (1989). ''Flora of Britain and Northern Europe''. ISBN 0-340-40170-2</ref><ref name=fop>Flora of Pakistan: [http://www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=200009201 ''Arabidopsis thaliana'']</ref><ref name=foc>Flora of China: [http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200009201 ''Arabidopsis thaliana'']</ref> Roots are simple in structure, with a single primary root that grows vertically downwards, later producing smaller lateral roots. These roots form interactions with [[Rhizosphere (ecology)|rhizosphere]] bacteria such as ''[[Bacillus megaterium]]''.<ref>{{cite journal |author=López-Bucio J, Campos-Cuevas JC, Hernández-Calderón E, ''et al'' |title=Bacillus megaterium rhizobacteria promote growth and alter root-system architecture through an auxin- and ethylene-independent signaling mechanism in Arabidopsis thaliana |journal=Mol. Plant Microbe Interact. |volume=20 |issue=2 |pages=207–17 |year=2007 |pmid=17313171 |doi=10.1094/MPMI-20-2-0207}}</ref>
Arabidopsis is native to [[Europe]], [[Asia]], and northwestern [[Africa]].  It is an [[annual plant|annual]] (rarely [[biennial plant|biennial]]) plant usually growing to 20–25 cm tall. The [[leaf|leaves]] form a rosette at the base of the plant, with a few leaves also on the flowering stem. The basal leaves are green to slightly purplish in colour, 1.5–5 cm long and 2–10 mm broad, with an entire to coarsely serrated margin; the stem leaves are smaller, unstalked, usually with an entire margin. Leaves are covered with small unicellular hairs (called [[trichome]]s). The [[flower]]s are 3 mm in diameter, arranged on an [[inflorescence]] with a helical [[phyllotaxy]]; their structure is that of the typical [[Brassicaceae|Brassicacaea]]. The [[fruit]] is a [[silique]] 5–20 mm long, containing 20–30 [[seed]]s. Roots are simple in structure, with a single primary root that grows vertically downwards, later producing smaller lateral roots.<ref name=fnwe>Flora of NW Europe: [http://ip30.eti.uva.nl/BIS/flora.php?selected=beschrijving&menuentry=soorten&id=2273 ''Arabidopsis thaliana'']</ref><ref name=blamey>Blamey, M. & Grey-Wilson, C. (1989). ''Flora of Britain and Northern Europe''. ISBN 0-340-40170-2</ref><ref name=fop>Flora of Pakistan: [http://www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=200009201 ''Arabidopsis thaliana'']</ref><ref name=foc>Flora of China: [http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200009201 ''Arabidopsis thaliana'']</ref>


Arabidopsis can complete its entire life cycle in six weeks. The central stem that produces flowers grows after about three weeks, and the flowers naturally self-pollinate. In the lab Arabidopsis may be grown in petri plates or pots, under fluorescent lights or in a greenhouse.<ref>{{cite journal|title=Arabidopsis thaliana: A Model Plant for Genome Analysis| author=D.W. Meinke, J.M. Cherry, C. Dean, S.D. Rounsley, M. Koornneef| journal=Science| year=1998|
Arabidopsis can complete its entire life cycle in six weeks (see the catalog subpage). The central stem that produces flowers grows after about three weeks, and the flowers naturally self-pollinate. In the laboratory Arabidopsis may be grown in petri plates or pots, under fluorescent lights or in a greenhouse.<ref>{{cite journal|title=Arabidopsis thaliana: A Model Plant for Genome Analysis| author=D.W. Meinke, J.M. Cherry, C. Dean, S.D. Rounsley, M. Koornneef| journal=Science| year=1998|volume=282| issue=5389| pages=662–682 | doi = 10.1126/science.282.5389.662}}</ref>
volume=282| issue=5389| pages=662–682 | doi = 10.1126/science.282.5389.662 <!--Retrieved from CrossRef by DOI bot-->
}}</ref>


==Use as a model organism==
==Use as a model organism==
Arabidopsis is widely used as one of the [[model organism]]s for studying [[plant sciences]], including [[genetics]] and plant development.<ref>{{cite journal |author=Rensink WA, Buell CR |title=Arabidopsis to rice. Applying knowledge from a weed to enhance our understanding of a crop species |journal=Plant Physiol. |volume=135 |issue=2 |pages=622–9 |year=2004 |pmid=15208410 |doi=10.1104/pp.104.040170}}</ref><ref>{{cite journal |author=Coelho SM, Peters AF, Charrier B, ''et al'' |title=Complex life cycles of multicellular eukaryotes: new approaches based on the use of model organisms |journal=Gene |volume=406 |issue=1-2 |pages=152–70 |year=2007 |pmid=17870254 |doi=10.1016/j.gene.2007.07.025}}</ref> It plays the role for agricultural sciences that [[Mus musculus|mice]] and [[Drosophila melanogaster|fruit flies (''Drosophila'')]] play in animal biology. Although ''Arabidopsis thaliana'' has little direct significance for agriculture, it has several traits that make it a useful model for understanding the genetic, cellular, and molecular biology of flowering plants.
{{Image|Cell size patterning in Arabidopsis flowers.png|right|350px|A [[confocal microscopy|confocal]] projection of the cluster of flowers surrounding the [[growing tip]] of Arabidopsis, showing the formation of [[cell (biology)|cells]] with a large range of sizes on the [[sepal]]s of the developing flowers. [[Nucleus (cell)|Cell nuclei]] and [[plasma membrane]]s are shown in green; [[chloroplast]]s are in red for contrast.}}


The small size of its [[genome]] make ''Arabidopsis thaliana'' useful for genetic mapping and [[sequencing]] &mdash; with about 157 million [[base pairs]]<ref>{{cite journal| author=Bennett, M. D., Leitch, I. J., Price, H. J., & Johnston, J. S.| year=2003| title=Comparisons with Caenorhabditis (100 Mb) and Drosophila (175 Mb) Using Flow Cytometry Show Genome Size in Arabidopsis to be 157 Mb and thus 25% Larger than the Arabidopsis Genome Initiative Estimate of 125 Mb| journal=Annals of Botany| volume=91| pages=547–557| doi= 10.1093/aob/mcg057 |  pmid=12646499}}</ref> and five [[chromosome]]s, Arabidopsis has one of the smallest genomes among plants. It was the first plant genome to be sequenced, completed in 2000 by the Arabidopsis Genome Initiative.<ref>{{cite journal| author=The Arabidopsis Genome Initiative| title=Analysis of the genome sequence of the flowering plant Arabidopsis thaliana| journal=Nature| year=2000| volume=408| pages=796–815| doi=10.1038/35048692 | pmid=11130711}}</ref> Much work has been done to assign functions to its 27,000 [[gene]]s and the 35,000 proteins they encode.<ref>{{cite web| title= Integr8 - A.thaliana Genome Statistics:| url=http://www.ebi.ac.uk/integr8/OrganismStatsAction.do;jsessionid=08E9058B5B688A4F7FF7D161CB9E36A4?orgProteomeId=3}}</ref>
Arabidopsis is widely used as one of the [[model species|model organism]]s for studying [[plant sciences]], including [[genetics]] and plant development.<ref>{{cite journal |author=Rensink WA, Buell CR |title=Arabidopsis to rice. Applying knowledge from a weed to enhance our understanding of a crop species |journal=Plant Physiol. |volume=135 |issue=2 |pages=622–9 |year=2004 |pmid=15208410 |doi=10.1104/pp.104.040170}}</ref><ref>{{cite journal |author=Coelho SM, Peters AF, Charrier B, ''et al'' |title=Complex life cycles of multicellular eukaryotes: new approaches based on the use of model organisms |journal=Gene |volume=406 |issue=1-2 |pages=152–70 |year=2007 |pmid=17870254 |doi=10.1016/j.gene.2007.07.025}}</ref> It plays the role for agricultural sciences that [[Mus musculus|mice]] and [[Drosophila melanogaster|fruit flies (''Drosophila'')]] play in animal biology. Although ''Arabidopsis thaliana'' has little direct significance for agriculture, it has several traits that make it a useful model for understanding the genetic, cellular, and molecular biology of flowering plants.
 
The small size of its [[genome]] make ''Arabidopsis thaliana'' useful for genetic mapping and [[sequencing]] &mdash; with about 157 million [[base pairs]]<ref>{{cite journal| author=Bennett, M. D., Leitch, I. J., Price, H. J., & Johnston, J. S.| year=2003| title=Comparisons with Caenorhabditis (100 Mb) and Drosophila (175 Mb) Using Flow Cytometry Show Genome Size in Arabidopsis to be 157 Mb and thus 25% Larger than the Arabidopsis Genome Initiative Estimate of 125 Mb| journal=Annals of Botany| volume=91| pages=547–557| doi= 10.1093/aob/mcg057 |  pmid=12646499}}</ref> and five [[chromosome]]s, Arabidopsis has one of the smallest genomes among plants. It was the first plant genome to be sequenced, completed in 2000 by the Arabidopsis Genome Initiative.<ref name="Genome"/> Much work has been done to assign functions to its 27,000 [[gene]]s and the 35,000 proteins they encode.<ref>{{cite web| title= Integr8 - A.thaliana Genome Statistics:| url=http://www.ebi.ac.uk/integr8/OrganismStatsAction.do;jsessionid=08E9058B5B688A4F7FF7D161CB9E36A4?orgProteomeId=3}}</ref>


The plant's small size and rapid life cycle are also advantageous for research. Having specialized as a [[spring ephemeral]], it has been used to found several laboratory strains that take about six weeks from germination to mature seed. The small size of the plant is convenient for cultivation in a small space and it produces many seeds. Further, the selfing nature of this plant assists genetic experiments. Also, as an individual plant can produce several thousand seeds, each of the above criteria leads to ''Arabidopsis thaliana'' being valued as a genetic model organism.
The plant's small size and rapid life cycle are also advantageous for research. Having specialized as a [[spring ephemeral]], it has been used to found several laboratory strains that take about six weeks from germination to mature seed. The small size of the plant is convenient for cultivation in a small space and it produces many seeds. Further, the selfing nature of this plant assists genetic experiments. Also, as an individual plant can produce several thousand seeds, each of the above criteria leads to ''Arabidopsis thaliana'' being valued as a genetic model organism.
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==History of Arabidopsis research==
==History of Arabidopsis research==
[[Image:Arabidopsis mutants.jpg|thumb|200px|A double flower mutant of Arabidopsis, first documented in 1873.]]
The first mutant in Arabidopsis was documented in 1873 by [[Alexander Braun]], describing a [[double flower]] phenotype (the mutated gene was likely ''Agamous'', cloned and characterized in 1990).<ref>{{cite journal| author=M.F. Yanofsky, H. Ma, J.L. Bowman, G.N. Drews, K.A. Feldmann & E.M. Meyerowitz| title=The protein encoded by the Arabidopsis homeotic gene agamous resembles transcription factors| year=1990| journal=Nature| volume=346| pages=35–39| doi=10.1038/346035a0 | pmid=1973265 | url=http://www.nature.com/nature/journal/v346/n6279/abs/346035a0.html}}</ref> However, it was not until 1943 that [[Friedrich Laibach]] (who had published the chromosome number in 1907) proposed Arabidopsis as a model organism.<ref name=meyerowitz2001>{{cite journal|author=E.M. Meyerowitz| title=Prehistory and History of Arabidopsis Research| journal=Plant Physiology| year=2001| volume=125| pages=15–19| url=http://www.plantphysiol.org/cgi/content/full/125/1/15 | pmid=11154286|doi=10.1038/346035a0}}</ref> His student Erna Reinholz published her thesis on Arabidopsis in 1945, describing the first collection of Arabidopsis mutants that they generated using [[x-ray]] [[mutagenesis]]. Laibach continued his important contributions to Arabidopsis research by collecting a large number of [[ecotype]]s. With the help of Albert Kranz, these were organised into the current ecotype collection of 750 natural accessions of ''Arabidopsis thaliana'' from around the world.
The first mutant in Arabidopsis was documented in 1873 by [[Alexander Braun]], describing a [[double flower]] phenotype (the mutated gene was likely ''Agamous'', cloned and characterized in 1990).<ref>{{cite journal| author=M.F. Yanofsky, H. Ma, J.L. Bowman, G.N. Drews, K.A. Feldmann & E.M. Meyerowitz| title=The protein encoded by the Arabidopsis homeotic gene agamous resembles transcription factors| year=1990| journal=Nature| volume=346| pages=35–39| doi=10.1038/346035a0 | pmid=1973265 | url=http://www.nature.com/nature/journal/v346/n6279/abs/346035a0.html}}</ref> However, it was not until 1943 that [[Friedrich Laibach]] (who had published the chromosome number in 1907) proposed Arabidopsis as a model organism.<ref name=meyerowitz2001>{{cite journal|author=E.M. Meyerowitz| title=Prehistory and History of Arabidopsis Research| journal=Plant Physiology| year=2001| volume=125| pages=15–19| url=http://www.plantphysiol.org/cgi/content/full/125/1/15 | pmid=11154286|doi=10.1038/346035a0}}</ref> His student Erna Reinholz published her thesis on Arabidopsis in 1945, describing the first collection of Arabidopsis mutants that they generated using [[x-ray]] [[mutagenesis]]. Laibach continued his important contributions to Arabidopsis research by collecting a large number of [[ecotype]]s. With the help of Albert Kranz, these were organised into the current ecotype collection of 750 natural accessions of ''Arabidopsis thaliana'' from around the world.


In the [[1950s#Science|1950s]] and [[1960s#Science|1960s]] [[John Langridge]] and [[George Rédei]] played an important role in establishing arabidopsis as a useful organism for biological laboratory experiments. Rédei wrote several scholarly reviews instrumental in introducing the model to the scientific community. The start of the arabidopsis research community dates to a newsletter called Arabidopsis Information Service (AIS), established in 1964. The first International Arabidopsis Conference was held in 1965, in [[Göttingen]], Germany.
In the [[1950s#Science|1950s]] and [[1960s#Science|1960s]] [[John Langridge]] and [[George Rédei]] played an important role in establishing arabidopsis as a useful organism for biological laboratory experiments. Rédei wrote several scholarly reviews instrumental in introducing the model to the scientific community. The start of the arabidopsis research community dates to a newsletter called Arabidopsis Information Service (AIS), established in 1964. The first International Arabidopsis Conference was held in 1965, in [[Göttingen]], Germany.


In the [[1980s#Science|1980s]] Arabidopsis started to become widely used in plant research laboratories around the world. It was one of several candidates that included [[maize]], [[petunia]] and [[tobacco]].<ref name=meyerowitz2001 /> The latter two were attractive since they were easily transformable with the then current technologies, while maize was a well established genetic model for plant biology. The breakthrough year for Arabidopsis as the preferred model plant came in 1986 when [[T-DNA]] mediated [[Transformation (genetics)#Plants|transformation]] was first published and this coincided with the first [[gene]] to be [[clone (genetics)|clone]]d and published.<ref>{{cite journal| author=Lloyd AM, Barnason AR, Rogers SG, Byrne MC, Fraley RT, Horsch RB| title=Transformation of Arabidopsis thaliana with Agrobacterium tumefaciens| year=1986| journal=Science| volume=234| pages=464–466 |  pmid=17792019 | doi=10.1126/science.234.4775.464 }}</ref><ref>{{cite journal|author=Chang C, Meyerowitz EM| title=Molecular cloning and DNA sequence of the Arabidopsis thaliana alcohol dehydrogenase gene| year=1986| journal=Proc Natl Acad Sci USA| volume=83| pages=1408–1412 |pmid=2937058 |doi=10.1073/pnas.83.5.1408}}</ref>
In the [[1980s#Science|1980s]] Arabidopsis started to become widely used in plant research laboratories around the world. It was one of several model organisms, that included [[maize]], [[petunia]] and [[tobacco]], used for basic research.<ref name=meyerowitz2001 /> The latter two were attractive since they were easily transformable with the then current technologies, while maize was a well established genetic model for plant biology. The breakthrough year for Arabidopsis as the preferred model plant came in 1986 when [[T-DNA]] mediated [[Transformation (genetics)#Plants|transformation]] was first published and this coincided with the first [[gene]] to be [[clone (genetics)|clone]]d and published.<ref>{{cite journal| author=Lloyd AM, Barnason AR, Rogers SG, Byrne MC, Fraley RT, Horsch RB| title=Transformation of Arabidopsis thaliana with Agrobacterium tumefaciens| year=1986| journal=Science| volume=234| pages=464–466 |  pmid=17792019 | doi=10.1126/science.234.4775.464 }}</ref><ref>{{cite journal|author=Chang C, Meyerowitz EM| title=Molecular cloning and DNA sequence of the Arabidopsis thaliana alcohol dehydrogenase gene| year=1986| journal=Proc Natl Acad Sci USA| volume=83| pages=1408–1412 |pmid=2937058 |doi=10.1073/pnas.83.5.1408}}</ref>
 
== Research ==
[[Image:ABC flower development.svg|thumb|150px|The ABC model of flower development was developed through study of Arabidopsis.]]
 
===Flower development===
Arabidopsis has been extensively studied as a model for flower development. The developing flower has four basic organs: [[sepal]]s, [[petal]]s, [[stamen]]s, and [[carpel]]s (which go on to form [[pistil]]s). These organs are arranged in a series of whorls: four sepals on the outer whorl, followed by six petals inside this, six stamens, and a central carpel region. [[Homeotic]] mutations in ''Arabidopsis'' result in the change of one organ to another &mdash; in the case of the Agamous mutation, for example, stamens become petals and carpels are replaced with a new flower, resulting in a recursively repeated sepal-petal-petal pattern.
 
Observations of homeotic mutations led to the formulation of the [[ABC model|ABC model of flower development]] by E. Coen and [[Elliot Meyerowitz|E. Meyerowitz]].<ref>{{cite journal |last=Coen |first=Henrico S. |coauthors=Elliot M. Meyerowitz |year=1991 |title=The war of the whorls: Genetic interactions controlling flower development |journal=Nature |volume=353 |issue= |pages=31–37 | pmid=1715520 | doi=10.1038/353031a0}}</ref> According to this model floral organ identity genes are divided into three classes: class A genes (which affect sepals and petals), class B genes (which affect petals and stamens), and class C genes (which affect stamens and carpels). These genes code for [[transcription factor]]s that combine to cause tissue specification in their respective regions during development. Although developed through study of ''Arabidopsis'' flowers, this model is generally applicable to other [[flowering plant]]s.
 
===Light sensing===
The photoreceptors [[phytochrome]] A, B, C, D and E mediate red light based phototropic response. Understanding the function of these receptors has helped plant biologists understand the signalling cascades that regulate [[photoperiodism]], [[germination]], [[de-etiolation]] and [[shade avoidance]] in plants.
 
Arabidopsis was used extensively in the study of the genetic basis of [[phototropism]], [[chloroplast]] alignment, and [[stomata]]l aperture and other blue light-influenced processes.<ref>{{cite journal |author=Sullivan JA, Deng XW |title=From seed to seed: the role of photoreceptors in Arabidopsis development |journal=Dev. Biol. |volume=260 |issue=2 |pages=289–97 |year=2003 |pmid=12921732 | doi = 10.1016/S0012-1606(03)00212-4 <!--Retrieved from CrossRef by DOI bot-->}}</ref> These traits respond to blue light, which is perceived by the [[phototropin]] light receptors. ''Arabidopsis'' has also been important in understanding the functions of another blue light receptor, [[cryptochrome]], which is especially important for light entrainment to control the plants [[circadian rhythm]]s.<ref>{{cite journal |author=Más P |title=Circadian clock signaling in Arabidopsis thaliana: from gene expression to physiology and development |journal=Int. J. Dev. Biol. |volume=49 |issue=5-6 |pages=491–500 |year=2005 |pmid=16096959 |doi=10.1387/ijdb.041968pm |url=http://www.intjdevbiol.com/paper.php?doi=10.1387/ijdb.041968pm}}</ref>
 
Light response was even found in roots, which were thought not to be particularly sensitive to light. While [[gravitropism|gravitropic]] response of ''Arabidopsis'' root organs is their predominant tropic response, specimens treated with [[mutagen]]s and selected for the absence of gravitropic action showed negative phototropic response to blue or white light, and positive response to red light.<ref>{{cite journal |author=Ruppel NJ, Hangarter RP, Kiss JZ |title=Red-light-induced positive phototropism in Arabidopsis roots |journal=Planta |volume=212 |issue=3 |pages=424–30 |year=2001 |pmid=11289607 | doi = 10.1007/s004250000410 <!--Retrieved from CrossRef by DOI bot-->}}</ref>
 
===Non-Mendelian inheritance===
In 2005, scientists at [[Purdue University]] proposed that ''Arabidopsis'' possessed an alternative to previously known mechanisms of [[DNA repair]], which one scientist called a "parallel path of [[Mendelian inheritance|inheritance]]". It was observed in [[mutation]]s of the ''HOTHEAD'' gene. Plants mutant in this gene exhibit organ fusion, and [[pollen]] can [[germinate]] on all plant surfaces, not just the [[Carpel|stigma]]. After spending over a year eliminating simpler explanations, it was indicated that the plants "cached" versions of their ancestors' genes going back at least four generations, and used these records as templates to correct the ''HOTHEAD'' mutation and other [[single nucleotide polymorphism]]s. The initial hypothesis proposed that the record may be [[RNA]]-based<ref>{{cite journal | journal=Nature | volume=434 | pages=505–9 | date=2005  | author=Lolle SJ, Victor JL, Young JM, Pruitt RE | title=Genome-wide non-mendelian inheritance of extra-genomic information in Arabidopsis | doi = 10.1038/nature03380 | pmid=15785770 }}[http://www.washingtonpost.com/wp-dyn/articles/A58349-2005Mar22_2.html Washington Post summary.]</ref> Since then, alternative models have been proposed which would explain the [[phenotype]] without requiring a new model of inheritance<ref>{{cite journal |author=Chaudhury, A. | date=2005 | title=Hothead healer and extragenomic information | journal=Nature | volume=437| pages=E1–E2| pmid=16136082| doi=10.1038/nature04062}}</ref><ref>{{cite journal | journal=Plant Cell | volume=17 | pages=2856–8 | date=2005  | author=Comai L, Cartwright RA | title=A toxic mutator and selection alternative to the non-Mendelian RNA cache hypothesis for hothead reversion |url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=16267378 | pmid=16267378 | doi =  10.1105/tpc.105.036293}} [http://www.dererumnatura.us/archives/2005/11/blog_about_hoth.html summary]</ref> More recently the whole phenomenon is being challenged as a being a simple artifact of pollen contamination.<ref>{{cite journal | author=Peng P., et al. |date=2006 | journal=Nature | title=Plant genetics: Increased outcrossing in hothead mutants | volume=443 | pages=E8–E9  | doi = 10.1038/nature05251 <!--Retrieved from CrossRef by DOI bot--> | pmid=17006468}}</ref> "''When Jacobsen took great pains to isolate the plants, he couldn't reproduce the [reversion] phenomenon''", notes [[Steven Henikoff]].<ref>{{cite journal
| journal=Science | volume=313 | pages=1864 | date=2006 
| author=Pennisi E | title=Genetics. Pollen contamination may explain controversial inheritance
| url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=17008492 | pmid=17008492 | doi = 10.1126/science.313.5795.1864}}</ref> In response to the new finding, Lolle and Pruitt agree that Peng ''et al''. did observe cross-pollination but note that some of their own data, such as double reversions of both mutant genes to the regular form, cannot be explained by cross pollination.<ref>{{cite journal| author=Lolle S. J., et al. | title=Increased outcrossing in hothead mutants (Reply)| journal=Nature| doi= 10.1038/nature05252 | volume=443 | pages=E8–E9 | pmid=17006468 | year = 2006}}</ref>
 
===Multigen===
This is an ongoing experiment on the [[International Space Station]], it is being performed by the [[European Space Agency]]. The goals are to study the growth and reproduction of plants from seed to seed in [[microgravity]].
 
== See also ==
{{wikispecies|Arabidopsis thaliana}}
* [[Botany]]
* [[Molecular biology]]
* [[Non-Mendelian inheritance]]
* [[Nottingham Arabidopsis Stock Centre]]


==References==
==References==
{{reflist|2}}
{{reflist|2}}
== External links ==
{{commons|Arabidopsis thaliana}}
*[http://www.arabidopsis.info The European Arabidopsis Stock Centre]
*[http://www.arabidopsis.org/ The Arabidopsis Information Resource (TAIR)]
*[http://www.aspb.org/publications/arabidopsis/ The Arabidopsis Book - comprehensive electronic book]
*[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Arabidopsis.html Arabidopsis thaliana: another "model organism"] from [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/ Kimball's Biology Pages]
*[http://signal.salk.edu/index.html Salk Institute Genomic Analysis Laboratory]
*Danish biotech firm [http://www.aresa.dk Aresa Biotection] uses a genetically modified thale cress to detect compounds like explosives (land mines)
*[http://www.genomenewsnetwork.org/articles/04_00/what_makes_plants.shtml What Makes Plants Grow? The Arabidopsis genome knows] Featured article in Genome News Network
*[http://www.nwo.nl/nwohome.nsf/pages/NWOA_6ZYL8N_Eng Thale cress goes on the defensive] Netherlands Organisation for Scientific Research
*[http://www.nasa.gov/mission_pages/station/science/experiments/Multigen.html Multigen at NASA.gov]

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Arabidopsis thaliana
Arabidopsis thaliana wild type 25 days old.jpg
Scientific classification
Kingdom: Plantae
(unranked) Eudicots
(unranked) Rosids
Order: Brassicales
Family: Brassicaceae
Genus: Arabidopsis
Species: A. thaliana
Binomial name
Arabidopsis thaliana
(L.) Heynh.
Synonyms

Arabis thaliana

Arabidopsis thaliana is a small flowering plant widely used by plant biologists as a model organism for basic research. It has several common names including thale cress, mouse-ear cress or just Arabidopsis).[1] It is popular for research since it has a relatively short life cycle and its genome is one of the smaller ones. Due to its prominence in research it was the first plant genome to be sequenced.[2]

Habitat, morphology, and life cycle

Arabidopsis is native to Europe, Asia, and northwestern Africa. It is an annual (rarely biennial) plant usually growing to 20–25 cm tall. The leaves form a rosette at the base of the plant, with a few leaves also on the flowering stem. The basal leaves are green to slightly purplish in colour, 1.5–5 cm long and 2–10 mm broad, with an entire to coarsely serrated margin; the stem leaves are smaller, unstalked, usually with an entire margin. Leaves are covered with small unicellular hairs (called trichomes). The flowers are 3 mm in diameter, arranged on an inflorescence with a helical phyllotaxy; their structure is that of the typical Brassicacaea. The fruit is a silique 5–20 mm long, containing 20–30 seeds. Roots are simple in structure, with a single primary root that grows vertically downwards, later producing smaller lateral roots.[3][4][5][6]

Arabidopsis can complete its entire life cycle in six weeks (see the catalog subpage). The central stem that produces flowers grows after about three weeks, and the flowers naturally self-pollinate. In the laboratory Arabidopsis may be grown in petri plates or pots, under fluorescent lights or in a greenhouse.[7]

Use as a model organism

A confocal projection of the cluster of flowers surrounding the growing tip of Arabidopsis, showing the formation of cells with a large range of sizes on the sepals of the developing flowers. Cell nuclei and plasma membranes are shown in green; chloroplasts are in red for contrast.

Arabidopsis is widely used as one of the model organisms for studying plant sciences, including genetics and plant development.[8][9] It plays the role for agricultural sciences that mice and fruit flies (Drosophila) play in animal biology. Although Arabidopsis thaliana has little direct significance for agriculture, it has several traits that make it a useful model for understanding the genetic, cellular, and molecular biology of flowering plants.

The small size of its genome make Arabidopsis thaliana useful for genetic mapping and sequencing — with about 157 million base pairs[10] and five chromosomes, Arabidopsis has one of the smallest genomes among plants. It was the first plant genome to be sequenced, completed in 2000 by the Arabidopsis Genome Initiative.[2] Much work has been done to assign functions to its 27,000 genes and the 35,000 proteins they encode.[11]

The plant's small size and rapid life cycle are also advantageous for research. Having specialized as a spring ephemeral, it has been used to found several laboratory strains that take about six weeks from germination to mature seed. The small size of the plant is convenient for cultivation in a small space and it produces many seeds. Further, the selfing nature of this plant assists genetic experiments. Also, as an individual plant can produce several thousand seeds, each of the above criteria leads to Arabidopsis thaliana being valued as a genetic model organism.

Finally, plant transformation in Arabidopsis is routine, using Agrobacterium tumefaciens to transfer DNA to the plant genome. The current protocol, termed "floral-dip", involves simply dipping a flower into a solution containing Agrobacterium, the DNA of interest, and a detergent.[12] This method avoids the need for tissue culture or plant regeneration.

History of Arabidopsis research

The first mutant in Arabidopsis was documented in 1873 by Alexander Braun, describing a double flower phenotype (the mutated gene was likely Agamous, cloned and characterized in 1990).[13] However, it was not until 1943 that Friedrich Laibach (who had published the chromosome number in 1907) proposed Arabidopsis as a model organism.[14] His student Erna Reinholz published her thesis on Arabidopsis in 1945, describing the first collection of Arabidopsis mutants that they generated using x-ray mutagenesis. Laibach continued his important contributions to Arabidopsis research by collecting a large number of ecotypes. With the help of Albert Kranz, these were organised into the current ecotype collection of 750 natural accessions of Arabidopsis thaliana from around the world.

In the 1950s and 1960s John Langridge and George Rédei played an important role in establishing arabidopsis as a useful organism for biological laboratory experiments. Rédei wrote several scholarly reviews instrumental in introducing the model to the scientific community. The start of the arabidopsis research community dates to a newsletter called Arabidopsis Information Service (AIS), established in 1964. The first International Arabidopsis Conference was held in 1965, in Göttingen, Germany.

In the 1980s Arabidopsis started to become widely used in plant research laboratories around the world. It was one of several model organisms, that included maize, petunia and tobacco, used for basic research.[14] The latter two were attractive since they were easily transformable with the then current technologies, while maize was a well established genetic model for plant biology. The breakthrough year for Arabidopsis as the preferred model plant came in 1986 when T-DNA mediated transformation was first published and this coincided with the first gene to be cloned and published.[15][16]

References

  1. Germplasm Resources Information Network: Arabidopsis thaliana
  2. 2.0 2.1 The Arabidopsis Genome Initiative (2000). "Analysis of the genome sequence of the flowering plant Arabidopsis thaliana". Nature 408: 796–815. DOI:10.1038/35048692. PMID 11130711. Research Blogging.
  3. Flora of NW Europe: Arabidopsis thaliana
  4. Blamey, M. & Grey-Wilson, C. (1989). Flora of Britain and Northern Europe. ISBN 0-340-40170-2
  5. Flora of Pakistan: Arabidopsis thaliana
  6. Flora of China: Arabidopsis thaliana
  7. D.W. Meinke, J.M. Cherry, C. Dean, S.D. Rounsley, M. Koornneef (1998). "Arabidopsis thaliana: A Model Plant for Genome Analysis". Science 282 (5389): 662–682. DOI:10.1126/science.282.5389.662. Research Blogging.
  8. Rensink WA, Buell CR (2004). "Arabidopsis to rice. Applying knowledge from a weed to enhance our understanding of a crop species". Plant Physiol. 135 (2): 622–9. DOI:10.1104/pp.104.040170. PMID 15208410. Research Blogging.
  9. Coelho SM, Peters AF, Charrier B, et al (2007). "Complex life cycles of multicellular eukaryotes: new approaches based on the use of model organisms". Gene 406 (1-2): 152–70. DOI:10.1016/j.gene.2007.07.025. PMID 17870254. Research Blogging.
  10. Bennett, M. D., Leitch, I. J., Price, H. J., & Johnston, J. S. (2003). "Comparisons with Caenorhabditis (100 Mb) and Drosophila (175 Mb) Using Flow Cytometry Show Genome Size in Arabidopsis to be 157 Mb and thus 25% Larger than the Arabidopsis Genome Initiative Estimate of 125 Mb". Annals of Botany 91: 547–557. DOI:10.1093/aob/mcg057. PMID 12646499. Research Blogging.
  11. Integr8 - A.thaliana Genome Statistics:.
  12. Zhang X, Henriques R, Lin SS, Niu QW, Chua NH (2006). "Agrobacterium-mediated transformation of Arabidopsis thaliana using the floral dip method". Nat Protoc 1 (2): 641–6. DOI:10.1038/nprot.2006.97. PMID 17406292. Research Blogging.
  13. M.F. Yanofsky, H. Ma, J.L. Bowman, G.N. Drews, K.A. Feldmann & E.M. Meyerowitz (1990). "The protein encoded by the Arabidopsis homeotic gene agamous resembles transcription factors". Nature 346: 35–39. DOI:10.1038/346035a0. PMID 1973265. Research Blogging.
  14. 14.0 14.1 E.M. Meyerowitz (2001). "Prehistory and History of Arabidopsis Research". Plant Physiology 125: 15–19. DOI:10.1038/346035a0. PMID 11154286. Research Blogging.
  15. Lloyd AM, Barnason AR, Rogers SG, Byrne MC, Fraley RT, Horsch RB (1986). "Transformation of Arabidopsis thaliana with Agrobacterium tumefaciens". Science 234: 464–466. DOI:10.1126/science.234.4775.464. PMID 17792019. Research Blogging.
  16. Chang C, Meyerowitz EM (1986). "Molecular cloning and DNA sequence of the Arabidopsis thaliana alcohol dehydrogenase gene". Proc Natl Acad Sci USA 83: 1408–1412. DOI:10.1073/pnas.83.5.1408. PMID 2937058. Research Blogging.