Superman (gene)

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Superman is a plant gene in Arabidopsis thaliana , that plays a role in controlling the boundary between stamen and carpel development in a flower. [1] It is named for the comic book character Superman, and the related genes kryptonite (gene) and clark kent were named accordingly (although, appropriately, the latter turned out to just be another form of superman). [2] It encodes a transcription factor (specifically a C2H2 type zinc finger protein). [3] Homologous genes are known in the petunia [4] and snapdragon, [5] which are also involved in flower development, although in both cases there are important differences from the functioning in Arabidopsis. Superman is expressed early on in flower development, in the stamen whorl adjacent to the carpel whorl. [4] It interacts with the other genes of the ABC model of flower development in a variety of ways. [4]

Contents

Gene function

Superman encodes a transcription factor. [3] This protein binds to the DNA through a zinc finger binding motif [3] acts as a regulator of floral homeotic genes, controlling the development of the flowers of Arabidopsis thaliana plants. Arabidopsis thaliana flowers develop in four whorls, which are concentric groups of cells branching off of the growing meristem. [6] Superman has been found to act in the fourth whorl of flowers, which would normally develop into Carpels. Superman normally restricts the effect of another gene called (APETALA3) in the fourth whorl, leaving APETALA3 expression only present in the second and third whorls. [6] APETALA3 is a gene normally associated with the development of a stamen in the third whorl, [7] so by its restriction, we allow for the development of other organs in the fourth whorl (such as the Pistil).

A mutation which completely removes superman gene function would result in flowers that carry extra stamens, replacing the pistils which would normally be developing in the fourth whorl. This mutation was named the sup-1 mutation. For the sup-1 mutation, More extreme stamen development is seen from a homozygous mutation than a heterozygous mutation. [8]

Interaction with the ABC model of flower development

The gene which Superman interacts with (APETALA3) is a member of the B-Function group of the ABC model of flower development, [7] which is typically responsible for the development of Stamen and Petals. Other important members of the ABC model of flower development include APETALA1, APETALA2, AGAMOUS, and PISTILATA. [9] Superman has not been found to interact with any of these other genes. SUPERMAN (SUP) and SUPERMAN-like genes such as APETALA2 work as a protein complex regulators with other corepressors known as TOPLESS (TPL) and a Histone Deacetylase 19 (HD19) in order to repress transcriptional functions in plants [10]

Epigenetic changes to Superman

Superman has been found to undergo to epigenetic modifications. Specifically, cytosine methylation (attachment of methyl radicals to cytosine bases), which represses its transcriptional activity. This methylation brings about the Clark Kent (clk) epialleles, which are a set of altered versions of the Superman gene lacking function. [11] Whereas most cases of cytosine methylation in plants tend to happen in the Promoter of transcription, the cytosine methylation of Superman happens within the gene, just after the promoter. [6] The exact location of the methylation varies, but defines which clk epiallele we define the plant as having; so far there are 7 identified clk epialleles (numbered clk1-clk7). [11]

These Clark Kent alleles can be inherited, but often, through mutation, will revert to the natural gene at a rate of about 3% per generation. [12]

Related Research Articles

<i>Arabidopsis thaliana</i> Model plant species in the family Brassicaceae

Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed.

<span class="mw-page-title-main">Meristem</span> Type of plant tissue involved in cell proliferation

The meristem is a type of tissue found in plants. It consists of undifferentiated cells capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants. These cells continue to divide until a time when they get differentiated and then lose the ability to divide.

<span class="mw-page-title-main">Homeosis</span>

In evolutionary developmental biology, homeosis is the transformation of one organ into another, arising from mutation in or misexpression of certain developmentally critical genes, specifically homeotic genes. In animals, these developmental genes specifically control the development of organs on their anteroposterior axis. In plants, however, the developmental genes affected by homeosis may control anything from the development of a stamen or petals to the development of chlorophyll. Homeosis may be caused by mutations in Hox genes, found in animals, or others such as the MADS-box family in plants. Homeosis is a characteristic that has helped insects become as successful and diverse as they are.

<span class="mw-page-title-main">ABC model of flower development</span> Model for genetics of flower development

The ABC model of flower development is a scientific model of the process by which flowering plants produce a pattern of gene expression in meristems that leads to the appearance of an organ oriented towards sexual reproduction, a flower. There are three physiological developments that must occur in order for this to take place: firstly, the plant must pass from sexual immaturity into a sexually mature state ; secondly, the transformation of the apical meristem's function from a vegetative meristem into a floral meristem or inflorescence; and finally the growth of the flower's individual organs. The latter phase has been modelled using the ABC model, which aims to describe the biological basis of the process from the perspective of molecular and developmental genetics.

<span class="mw-page-title-main">Primordium</span> Organ in the earliest recognizable stage of embryonic development

A primordium in embryology, is an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells. A primordium is the simplest set of cells capable of triggering growth of the would-be organ and the initial foundation from which an organ is able to grow. In flowering plants, a floral primordium gives rise to a flower.

The MADS box is a conserved sequence motif. The genes which contain this motif are called the MADS-box gene family. The MADS box encodes the DNA-binding MADS domain. The MADS domain binds to DNA sequences of high similarity to the motif CC[A/T]6GG termed the CArG-box. MADS-domain proteins are generally transcription factors. The length of the MADS-box reported by various researchers varies somewhat, but typical lengths are in the range of 168 to 180 base pairs, i.e. the encoded MADS domain has a length of 56 to 60 amino acids. There is evidence that the MADS domain evolved from a sequence stretch of a type II topoisomerase in a common ancestor of all extant eukaryotes.

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<span class="mw-page-title-main">Apetala 2</span> Protein in Arabidopsis

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Evolutionary developmental biology (evo-devo) is the study of developmental programs and patterns from an evolutionary perspective. It seeks to understand the various influences shaping the form and nature of life on the planet. Evo-devo arose as a separate branch of science rather recently. An early sign of this occurred in 1999.

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"Double-flowered" describes varieties of flowers with extra petals, often containing flowers within flowers. The double-flowered trait is often noted alongside the scientific name with the abbreviation fl. pl.. The first abnormality to be documented in flowers, double flowers are popular varieties of many commercial flower types, including roses, camellias and carnations. In some double-flowered varieties all of the reproductive organs are converted to petals — as a result, they are sexually sterile and must be propagated through cuttings. Many double-flowered plants have little wildlife value as access to the nectaries is typically blocked by the mutation.

<span class="mw-page-title-main">PRC2</span>

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Agamous (AG) is a homeotic gene and MADS-box transcription factor from Arabidopsis thaliana. The TAIR AGI number is AT4G18960.

Homeotic genes are genes which regulate the development of anatomical structures in various organisms such as echinoderms, insects, mammals, and plants. Homeotic genes often encode transcription factor proteins, and these proteins affect development by regulating downstream gene networks involved in body patterning.

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Detlef Weigel is a German American scientist working at the interface of developmental and evolutionary biology.

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Epigenetics is the study of changes in gene expression that occur via mechanisms such as DNA methylation, histone acetylation, and microRNA modification. When these epigenetic changes are heritable, they can influence evolution. Current research indicates that epigenetics has influenced evolution in a number of organisms, including plants and animals.

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<span class="mw-page-title-main">RNA-directed DNA methylation</span> RNA-based gene silencing process

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References

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  2. "Clever Arabidopsis gene names". Clever gene names. Mikael Niku and Mikko Taipale. 2005-12-03. Archived from the original on 2006-12-31. Retrieved 2007-01-23.
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  10. Krogan, N. T., Hogan, K., & Long, J. A. (2012). APETALA2 negatively regulates multiple floral organ identity genes in Arabidopsis by recruiting the co-repressor TOPLESS and the histone deacetylase HDA19. Development, dev-085407.
  11. 1 2 Jacobsen, Steven E.; Meyerowitz, Elliot M. (1997-08-22). "Hypermethylated SUPERMAN Epigenetic Alleles in Arabidopsis". Science. 277 (5329): 1100–1103. doi:10.1126/science.277.5329.1100. ISSN   0036-8075. PMID   9262479.
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