MADS-box transcription factors are found throughout the eukaryotes where they function in diverse processes such as cardiac muscle development and signal transduction (animals), pheromone responses (yeast), and the development of flowers, roots, meristems, and leaves (plants).  There are two major types of MADS-box genes whose distribution indicates that there had already been a gene duplication of MADS-box transcription factors in the last common ancestor of the higher eukaryotes (Alvarez-Buylla, 2000; Kaufmann, 2005).

     MADS box transcription factors can possess several domains, including a keratin-like domain and one domain is only known in plants.  A homeotic MADS box transcription factor was present in the common ancestor of higher plants.  Ferns and seed plants possess different subfamilies of MADS box transcription factors and a number of groups are shared among seed plants.  Some of these proteins are important in angiosperms in determining the identity of floral structures (Munster, 1997; Kaufmann, 2005). MADS-box transcription factors seem to have originally functioned in the haploid life stages of the algae ancestral to land plants, only to later be adapted for the terrestrial diploid stage of land plants (Tanabe, 2005).


The eukaryotic Rel family of transcription factors coordinate responses to stress and pathogens.  While one Rel homolog in Drosophila functions in responses to bacteria, another is involved in the formation of the embryonic dorsal/ventral axis.  Rel proteins can bind DNA as homodimers, heterodimers, or as part of a multiprotein complex composed of various proteins.

    In humans, 2 Rel family members (p50 and p65) can bind DNA as homodimers or as the heterodimer NF-κB which activates the light chain immunoglobulin locus in response to stress.  The DNA-binding region of p50 is similar to that of p53 and p50 homodimers bind to MHC I enhancers.

     Coelomates share a family of Rel family inhibitors called IκBs which possess repeats of the ankyrin domain (Chytil, 1996).



The Drosophila gene glial cells missing (gcm) was the first known member of a new kind of DNA-binding protein.  Homologs exist in mice and humans (Akiyama, 1996).


The ets family of transcription factors is shared among coelomates (Laudet, 1993). 



A zinc-finger-like protein domain, called the DM domain, evolved as a bilateran transcription factor. Members of the Dmrt gene family include mab-3 in nematodes, doublesex in fruit flies, and XDmrt4 which regulates the development of the olfactory epithelium (Huang, 2005).


There are three members of the Maf gene family of leucine zipper proteins.  They are required for the differentiation of keratinocytes and null mutations in mice are lethal (Motohashi, 2004).  


The Drosophila leucine zipper protein Bicaudal was originally recognized for its role in the developing oocyte.  It is now know to be shared among bilaterans and it is most expressed in the brain and muscle in mammals (Baens, 1997).

Humans and mice share pseudogenes of a bHLH leucine zipper transcription factors (Pourcel, 2000).