Transcription factor that specifically binds AT-rich DNA sequences related to the nuclear matrix attachment regions (MARs). Binds to the MARs present in the ETTIN (ETT) promoter leading to a negative regulation of its gene expression. Functions as a molecular node downstream of the homeotic protein AGAMOUS (AG), regulating patterning and differentiation of reproductive organs. Acts as a chromatin remodeling factor that modifies the architecture of ETTIN (ETT) chromatin by modulating H3 methylation leading to the regulation of ETT expression. Seems to be involved in the regulation of a set of reproductives genes including CRABS CLAW (CRC), JAGGED (JAG) and KNUCKLES (KNU). Preferentially expressed in roots, but also in flowers and leaves. Detected in the inflorescence meristem, floral primordia and developing reproductive organs. Expressed throughout floral primordia at stages 1 through 4. At stage 6 and later, expression is confined to reproductive organ primordia. At stages later than stage 10, localizes in developing ovules and anther locules. The PPC domain mediates interactions between AHL proteins. Reproductive defects. Overexpression of AHL21 results in reproductive defects such as excessive outgrowth of stigmatic tissues, short valves, and excessive proliferation of a carpelloid organ at the lateral side of a pistil with exposed ovules.