TheMADS box is a conservedsequence motif. The genes which contain this motif are called the MADS-box gene family.[1] 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.[2] MADS-domain proteins are generallytranscription factors.[2][3] 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.[4][5][6][7] There is evidence that the MADS domain evolved from a sequence stretch of atype II topoisomerase in a common ancestor of all extant eukaryotes.[8]
The first MADS-box gene to be identified wasARG80 from budding yeast,Saccharomyces cerevisiae,[9] 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,[1] ignoringARG80:
InA. thaliana,A. majus, andZea mays this motif is involved in floral development. Early study in these model angiosperms was the beginning of research into themolecular evolution of floral structure in general, as well as their role in nonflowering plants.[11]
MADS-box genes have been detected in nearly all eukaryotes studied.[8] While the genomes of animals and fungi generally possess only around one to five MADS-box genes, genomes offlowering plants have around 100 MADS-box genes.[12][13]Two types of MADS-domain proteins are distinguished; the SRF-like or Type I MADS-domain proteins and the MEF2-like (afterMYOCYTE-ENHANCER-FACTOR2) or Type II MADS-domain proteins.[8][13] SRF-like MADS-domain proteins in animals and fungi have a second conserved domain, the SAM (SRF, ARG80, MCM1) domain.[14] MEF2-like MADS-domain proteins in animals and fungi have theMEF2 domain as a second conserved domain.[14] 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 aC-terminal domain.[12] In plants, MADS-domain protein form tetramers and this is thought to be central for their function.[15][16] The structure of the tetramerisation domain of the MADS-domain protein SEPALLATA3 was solved illustrating the structural basis for tetramer formation[17]
MADS-box genes have a variety of functions. In animals, MADS-box genes are involved in muscle development andcell proliferation and differentiation.[14] Functions in fungi range from pheromone response toarginine metabolism.[14]
In plants, MADS-box genes are involved in controlling all major aspects of development, including male and femalegametophyte development, embryo and seed development, as well as root, flower and fruit development.[12][13]
Some MADS-box genes of flowering plants have homeotic functions like theHOX genes of animals.[1] The floral homeotic MADS-box genes (such asAGAMOUS andDEFICIENS) participate in the determination of floral organ identity according to theABC model of flower development.[20]
Another function of MADS-box genes is flowering time determination. InArabidopsis thaliana the MADS box genesSOC1[21] andFlowering Locus C[22] (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 offlowering, and help to ensure that fertilization occurs at the time of maximal reproductive potential.
^Lü S, Du X, Lu W, Chong K, Meng Z (2007). "Two AGAMOUS-like MADS-box genes from Taihangia rupestris (Rosaceae) reveal independent trajectories in the evolution of class C and class D floral homeotic functions".Evolution & Development.9 (1):92–104.doi:10.1111/j.1525-142X.2006.00140.x.PMID17227369.S2CID9253584.
^abcGramzow L, Ritz MS, Theissen G (April 2010). "On the origin of MADS-domain transcription factors".Trends in Genetics.26 (4):149–53.doi:10.1016/j.tig.2010.01.004.PMID20219261.
^Dubois E, Bercy J, Descamps F, Messenguy F (1987). "Characterization of two new genes essential for vegetative growth in Saccharomyces cerevisiae: nucleotide sequence determination and chromosome mapping".Gene.55 (2–3):265–275.doi:10.1016/0378-1119(87)90286-1.PMID3311883.
^abcBecker A, Theissen G (December 2003). "The major clades of MADS-box genes and their role in the development and evolution of flowering plants".Molecular Phylogenetics and Evolution.29 (3):464–89.doi:10.1016/S1055-7903(03)00207-0.PMID14615187.
^Riechmann, Jose Luis; Meyerowitz, Elliot M. (1997). "MADS Domain Proteins in Plant Development".Biological Chemistry.378 (10):1079–1101.ISSN1431-6730.PMID9372178.
