In "A. thaliana", function A is mainly represented by two genes "APETALA1" ("AP1)" and "APETALA2" ("AP2") "AP1" is a MADS-box type gene, while "AP2" belongs to the family of genes that contains AP2, which it gives its name to and which consists of transcription factors that are only found in plants. AP2 has also been shown to complex with the co-repressor TOPLESS (TPL) in developing floral buds to repress the C-class gene "AGAMOUS" ("AG"). However, "AP2" is not expressed in the shoot apical meristem (SAM), which contains the latent stem cell population throughout the adult life of "Arabidopsis", and so it is speculated that TPL works with some other A-class gene in the SAM to repress "AG"."AP1" functions as a type A gene, both in controlling the identity of sepals and petals, and it also acts in the floral meristem. "AP2" not only functions in the first two verticils, but also in the remaining two, in developing ovules and even in leaves. It is also likely that post-transcriptional regulation exists, which controls its A function, or even that it has other purposes in the determination of organ identity independent of that mentioned here.