MADS-box
Encyclopedia
The MADS box is a conserved sequence motif
found in genes which comprise 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.
, but was at that time not recognized as a member of a large gene family. The MADS-box gene family got its name later as an acronym referring to the four founding members, ignoring ARG80:
Two types of MADS-domain proteins are distinguished; the SRF-like or Type I MADS-domain proteins and the MEF2-like (after MYOCYTE-ENHANCER-FACTOR2
) or Type II MADS-domain proteins. SRF-like MADS-domain proteins in animals and fungi have a second conserved domain, the SAM (SRF, ARG80, MCM1) domain. MEF2-like MADS-domain proteins in animals and fungi have the MEF2
domain as a second conserved domain. In plants, the MEF2-like MADS-domain proteins are also termed MIKC-type proteins referring to their conserved domain structure, where the MADS (M) domain is followed by an Intervening (I), a Keratin-like (K) and a C-terminal domain.
metabolism.
In plants, MADS-box genes are involved in controlling all major aspects of development, including male and female gametophyte
development, embryo and seed development, as well as root, flower and fruit development.
Some MADS-box genes of flowering plants have homeotic functions like the HOX genes of animals. The floral homeotic MADS-box genes (such as AGAMOUS and DEFICIENS) participate in the determination of floral organ identity according to the ABC model of flower development.
Another function of MADS-box genes is flowering time determination. In Arabidopsis thaliana
the MADS box genes SOC1 and Flowering Locus C
(FLC) have been shown to have an important role in the integration of molecular flowering time pathways. These genes are essential for the correct timing of flowering, and help to ensure that fertilization occurs at the time of maximal reproductive potential.
Sequence motif
In genetics, a sequence motif is a nucleotide or amino-acid sequence pattern that is widespread and has, or is conjectured to have, a biological significance...
found in genes which comprise 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
Type II topoisomerase
Type II topoisomerases cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils. They use the hydrolysis of ATP, unlike type I topoisomerase. In this process, these enzymes change the linking number of circular DNA by +/-2....
in a common ancestor of all extant eukaryotes.
Origin of name
The first MADS-box gene to be identified was ARG80 from budding yeast, Saccharomyces cerevisiaeSaccharomyces cerevisiae
Saccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental to baking and brewing since ancient times. It is believed that it was originally isolated from the skin of grapes...
, but was at that time not recognized as a member of a large gene family. The MADS-box gene family got its name later as an acronym referring to the four founding members, ignoring ARG80:
- MCM1 from the budding yeast, Saccharomyces cerevisiaeSaccharomyces cerevisiaeSaccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental to baking and brewing since ancient times. It is believed that it was originally isolated from the skin of grapes...
, - AGAMOUSAgamousAGAMOUS is a gene and transcription factor for Arabidopsis thaliana. The TAIR ATG number is AT4G18960.-External links:*...
from the thale cress Arabidopsis thalianaArabidopsis thalianaArabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
, - DEFICIENS from the snapdragon Antirrhinum majusAntirrhinum majusAntirrhinum majus is a species of plants belonging to the genus Antirrhinum...
, - SRFSerum response factorSerum response factor , also known as SRF, is a transcription factor.It is a member of the MADS box superfamily of transcription factors. This protein binds to the serum response element in the promoter region of target genes...
from the human Homo sapiens.
Diversity
MADS-box genes were detected in nearly all eukaryotes studied. While the genomes of animals and fungi generally possess only around one to five MADS-box genes, genomes of flowering plants have around 100 MADS-box genes.Two types of MADS-domain proteins are distinguished; the SRF-like or Type I MADS-domain proteins and the MEF2-like (after MYOCYTE-ENHANCER-FACTOR2
Mef2
In the field of molecular biology, myocyte enhancer factor-2 proteins are a family of transcription factors which through control of gene expression are important regulators of cellular differentiation and consequently play a critical role in embryonic development. In adult organisms, Mef2...
) or Type II MADS-domain proteins. SRF-like MADS-domain proteins in animals and fungi have a second conserved domain, the SAM (SRF, ARG80, MCM1) domain. MEF2-like MADS-domain proteins in animals and fungi have the MEF2
Mef2
In the field of molecular biology, myocyte enhancer factor-2 proteins are a family of transcription factors which through control of gene expression are important regulators of cellular differentiation and consequently play a critical role in embryonic development. In adult organisms, Mef2...
domain as a second conserved domain. In plants, the MEF2-like MADS-domain proteins are also termed MIKC-type proteins referring to their conserved domain structure, where the MADS (M) domain is followed by an Intervening (I), a Keratin-like (K) and a C-terminal domain.
Function of MADS-box genes
MADS-box genes have a variety of functions. In animals, MADS-box genes are involved in muscle development and cell proliferation and differentiation. Functions in fungi range from pheromone response to arginineArginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
metabolism.
In plants, MADS-box genes are involved in controlling all major aspects of development, including male and female gametophyte
Gametophyte
A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
development, embryo and seed development, as well as root, flower and fruit development.
Some MADS-box genes of flowering plants have homeotic functions like the HOX genes of animals. The floral homeotic MADS-box genes (such as AGAMOUS and DEFICIENS) participate in the determination of floral organ identity according to the ABC model of flower development.
Another function of MADS-box genes is flowering time determination. In Arabidopsis thaliana
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
the MADS box genes SOC1 and Flowering Locus C
Flowering Locus C
Flowering Locus C is a MADS-box gene that in late-flowering ecotypes of the plant Arabidopsis thaliana is responsible for vernalization. In a new seedling FLC is expressed, which prevents flowering. Upon exposure to cold, less FLC is expressed , and flowering becomes possible...
(FLC) have been shown to have an important role in the integration of molecular flowering time pathways. These genes are essential for the correct timing of flowering, and help to ensure that fertilization occurs at the time of maximal reproductive potential.