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Arabidopsis thaliana

Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Brassicales
Family: Brassicaceae
Genus: Arabidopsis
Species: A. Plants are living Organisms belonging to the kingdom Plantae. The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group Magnoliopsida is the Botanical name for a class of Flowering plants By definition the class will include the family Magnoliaceae, but its The Brassicales are an order of Flowering plants belonging to the Eurosids II group of Dicotyledons under the APG II system Brassicaceae or Cruciferae, also known as the crucifers, the mustard family or cabbage family is a family (the third lowest primary Arabidopsis ( A-ra-bi-dóp-sis, rockcress) is a genus in the family Brassicaceae. thaliana
Binomial name
Arabidopsis thaliana
(L.) Heynh. Carl Linnaeus (Latinized as Carolus Linnaeus, also known after his ennoblement as, May 23 new style (13 May old style 1707 who laid the foundations for

Synonyms

Arabis thaliana

Arabidopsis thaliana (A-ra-bi-dóp-sis tha-li-á-na; thale cress, mouse-ear cress or Arabidopsis), is small flowering plant native to Europe, Asia, and northwestern Africa. In Scientific nomenclature, synonyms are different Scientific names used for a single Taxon. Syllable stress of botanical names varies with the language spoken [1] A spring annual with a relatively short life cycle, Arabidopsis is popular as a model organism in plant biology and genetics. A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made Its genome is one of the smallest plant genomes and was the first plant genome to be sequenced. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Arabidopsis is a popular tool for understanding the molecular biology of many plant traits, including flower development and light sensing. Molecular biology is the study of Biology at a molecular level A flower, also known as a bloom or Blossom, is the reproductive structure found in Flowering plants (plants of the division Magnoliophyta, also Phototropism is directional growth in which the direction of growth is determined by the direction of the light source

Contents

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. Botanically an annual plant is a Plant that usually germinates, Flowers and dies in one Year. A biennial plant is a flowering Plant that takes two years to complete its lifecycle. The leaves form a rosette at the base of the plant, with a few leaves also on the flowering stem. In Botany, a leaf is an above-ground Plant organ specialized for Photosynthesis. 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). Trichomes, from the Greek meaning "growth of Hair " are fine outgrowths or appendages on Plants and certain Protists These are of diverse The flowers are 3 mm in diameter, arranged in a corymb; their structure is that of the typical Brassicacaea. A flower, also known as a bloom or Blossom, is the reproductive structure found in Flowering plants (plants of the division Magnoliophyta, also An inflorescence is a group or cluster of Flowers arranged on a stem that is composed of a main Branch or a complicated arrangement of branches Brassicaceae or Cruciferae, also known as the crucifers, the mustard family or cabbage family is a family (the third lowest primary The fruit is a siliqua 5–20 mm long, containing 20–30 seeds. The term fruit has different meanings dependent on context and the term is not synonymous in Food preparation and Biology. Brassicaceae or Cruciferae, also known as the crucifers, the mustard family or cabbage family is a family (the third lowest primary A seed (in some plants referred to as a kernel) is a small embryonic Plant enclosed in a covering called the seed coat usually with some stored [2][3][4][5] 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 bacteria such as Bacillus megaterium. Rhizosphere is the narrow region of Soil that is directly influenced by Root secretions and associated soil Microorganisms ref> Bacillus megaterium is a rod-shaped Gram-positive species of Bacteria used as a Soil inoculant in Agriculture and Horticulture [6]

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. [7]

Use as a model organism

Arabidopsis is widely used as one of the model organisms for studying plant sciences, including genetics and plant development. A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made Botany, plant science(s, phytology, or plant biology is a branch of Biology and is the scientific study of plant Life Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is [8][9] It plays the role for agricultural sciences that mice and fruit flies (Drosophila) play in animal biology. The House Mouse ( Mus musculus) is one of the most numerous species of the genus Mus commonly termed a Mouse. Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order 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. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby For the sense of "sequencing" used in Electronic music, see the Music sequencer article In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called A chromosome is an organized structure of DNA and Protein that is found in cells. It was the first plant genome to be sequenced, completed in 2000 by the Arabidopsis Genome Initiative. [11] Much work has been done to assign functions to its 27,000 genes and the 35,000 proteins they encode. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance [12]

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. An ephemeral plant marked by short life cycles usually six to eight weeks 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. In Molecular biology, transformation is the genetic alteration of a cell resulting from the uptake genomic incorporation and expression of foreign Agrobacterium tumefaciens is the causal agent of Crown Gall disease (the formation of Tumours in over 140 species of Dicot. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known The current protocol, termed "floral-dip", involves simply dipping a flower into a solution containing Agrobacterium, the DNA of interest, and a detergent. [13] This method avoids the need for tissue culture or plant regeneration. Tissue culture is the growth of tissues and/or cells separate from the organism

History of Arabidopsis research

A double flower mutant of Arabidopsis, first documented in 1873.
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). Alexander Carl Heinrich Braun ( May 10, 1805 - March 29, 1877) was a German Botanist from Regensburg, Bavaria " Double-flowered " describes varieties of Flowers with extra Petals often containing flowers within flowers [14] However, it was not until 1943 that Friedrich Laibach (who had published the chromosome number in 1907) proposed Arabidopsis as a model organism. [15] 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. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. A process by which the genetic information of an Organism is changed in a stable manner either in nature or experimentally by the use of Chemicals or Radiation. Laibach continued his important contributions to Arabidopsis research by collecting a large number of ecotypes. Within a Species, an ecotype is a genetically unique Population that is adapted to its local environment 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. The 1950s Decade refers to the years of 1950 to 1959 inclusive The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 John George Langridge ( 10 February 1910 – 27 June 1999) was a Cricketer who played for Sussex. 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. Göttingen ( ˈgœtɪŋən, Low German: Chöttingen is a College town in Lower Saxony, Germany.

In the 1980s Arabidopsis started to become widely used in plant research laboratories around the world. The 1980s was the decade spanning from January 1 1980 to December 31 1989. It was one of several candidates that included maize, petunia and tobacco. Maize (ˈmeɪz ( Zea mays L. ssp mays) known as corn in some countries is a cereal grain domesticated in Mesoamerica For Petunia Pig, a Looney Tunes character see Petunia Pig For Aunt Petunia see Aunt Petunia For Tobacco is an Agricultural product recognized as an addictive drug processed from the fresh Leaves of plants in the genus Nicotiana. [15] 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. T-DNA is the transferred DNA of the tumor-inducing (Ti plasmid of some species of bacteria such as Agrobacterium tumefaciens and In Molecular biology, transformation is the genetic alteration of a cell resulting from the uptake genomic incorporation and expression of foreign History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it In vivo. [16][17]

Research

The ABC model of flower development was developed through study of Arabidopsis.
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: sepals, petals, stamens, and carpels (which go on to form pistils). A sepal (from Latin separatus "separate" + petalum "petal" is a part of the flower of Angiosperms or flower plants A petal (from Ancient Greek petalon "leaf" "thin plate" regarded as a highly modified leaf is one member or part of the corolla The stamen ( Plural stamina or stamens, from Latin stamen meaning "thread of the warp " is the male A gynoecium (from Ancient Greek gyne, "woman" is the Female reproductive part of a Flower. A gynoecium (from Ancient Greek gyne, "woman" is the Female reproductive part of a Flower. 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 — 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. Homeosis is the transformation of one body part into another arising from Mutation in or misexpression of specific developmentally critical Genes It may be caused

Observations of homeotic mutations led to the formulation of the ABC model of flower development by E. Coen and E. Meyerowitz. Elliot Meyerowitz (born May 22, 1951) is a US biologist He is currently George W [18] 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 factors that combine to cause tissue specification in their respective regions during development. In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences Although developed through study of Arabidopsis flowers, this model is generally applicable to other flowering plants. The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group

Light sensing

The photoreceptors phytochrome A, B, C, D and E mediate red light based phototropic response. Phytochrome is a Photoreceptor, a Pigment that Plants use to detect light 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. Photoperiodicity is the physiological reaction of organisms to the length of day or night Germination is the process whereby growth emerges from a period of dormancy Etiolation occurs when plants are grown in either partial or complete absence of light and is characterized by long weak stems smaller sparser leaves due to longer internodes and a Shade avoidance is a set of responses that plants display when they are subjected to the Shade of another plant

Arabidopsis was used extensively in the study of the genetic basis of phototropism, chloroplast alignment, and stomatal aperture and other blue light-influenced processes. Phototropism is directional growth in which the direction of growth is determined by the direction of the light source Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. In Botany, a stoma (also stomate; plural stomata) is a tiny opening or pore found mostly on the underside of a Plant Leaf [19] These traits respond to blue light, which is perceived by the phototropin light receptors. Phototropins are Photoreceptor proteins (specifically Flavoproteins that mediate Phototropism responses in higher Plants. 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 rhythms. Cryptochrome is a name used for the Blue Light Photoreceptors of Plants and Animals The word cryptochrome derives from [20]

Light response was even found in roots, which were thought not to be particularly sensitive to light. While gravitropic response of Arabidopsis root organs is their predominant tropic response, specimens treated with mutagens and selected for the absence of gravitropic action showed negative phototropic response to blue or white light, and positive response to red light. Gravitropism ''geotropism'' is a turning or growth movement by a Plant or Fungus in response to Gravity. In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) [21]

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 inheritance". DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent It was observed in mutations of the HOTHEAD gene. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Plants mutant in this gene exhibit organ fusion, and pollen can germinate on all plant surfaces, not just the stigma. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of Germination is the process whereby growth emerges from a period of dormancy A gynoecium (from Ancient Greek gyne, "woman" is the Female reproductive part of a Flower. 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 polymorphisms. A single nucleotide polymorphism ( SNP, pronounced snip) is a DNA sequence variation occurring when a single Nucleotide - A, T The initial hypothesis proposed that the record may be RNA-based[22] Since then, alternative models have been proposed which would explain the phenotype without requiring a new model of inheritance[23][24] More recently the whole phenomenon is being challenged as a being a simple artifact of pollen contamination. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties [25] "When Jacobsen took great pains to isolate the plants, he couldn't reproduce the [reversion] phenomenon", notes Steven Henikoff. [26] 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. [27]

Multigen

This is an ongoing experiment on the International Space Station, it is being performed by the European Space Agency. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member The goals are to study the growth and reproduction of plants from seed to seed in microgravity.

See also

References

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