In "A. thaliana" the type-B function mainly arises from two genes, "APETALA3" ("AP3") and "PISTILLATA" ("PI"), both of which are MADS-box genes. A mutation of either of these genes causes the homeotic conversion of petals into sepals and of stamens into carpels. This also occurs in its orthologs in "A. majus", which are DEFICIENS ("DEF") and "GLOBOSA" ("GLO") respectively. For both species the active form of binding with DNA is that derived from the heterodimer: AP3 and PI, or DEF and GLO, dimerize. This is the form in which they are able to function.