Probable transcription factor involved in cell specification and pattern formation during embryogenesis. Binds to the L1 box DNA sequence 5'-TAAATG[CT]A-3'. Plays a role in maintaining the identity of L1 cells, possibly by interacting with their L1 box or other target-gene promoters; binds to the LIP1 gene promoter and stimulates its expression upon imbibition (PubMed:24989044). Acts as a positive regulator of gibberellins (GAs)-regulated epidermal gene expression (e.g. LIP1, LIP2, LTP1, FDH and PDF1) (PubMed:24989044). Functionally redundant to PDF2 (PubMed:24989044). Seems to promote cell differentiation (PubMed:25564655). Interacts with GAI/RGA2, RGA/RGA1/GRS, RGL2/SCL19 and PDF2 (PubMed:24989044). Interacts with AIL7/PLT7, ANT, BBM and AIL1 (PubMed:25564655). First expressed in the apical cell after the first asymmetric division of the zygote. Expressed in all proembryo cells until the eight-cell stage, and then restricted to the protoderm in the 16-cell proembryo. Not detected in the torpedo stage, but reappeared later in the L1 layer of the shoot apical meristem in the mature embryo. After germination, the L1 layer-specific expression pattern is maintained in the vegetative shoot apical meristem, inflorescence, floral meristems, and the young floral organ primordia. Finally, expressed in the protoderm of the ovule primordia and integuments and gradually restricted to the endothelium surrounding the embryo sac. Stimulated during seed imbibition (PubMed:24989044). Induced by gibberellins (GAs) and repressed by DELLA proteins in an ATML1- and PDF2-dependent manner (PubMed:24989044). Upon seed imbibition, increased GA levels in the epidermis reduce DELLA proteins (e.g. GAI/RGA2, RGA/RGA1/GRS and RGL2/SCL19) abundance and release, in turn, ATML1 and PDF2 which activate LIP1 expression, thus enhancing germination potential (PubMed:24989044). Plants missing both PDF2 and ATML1 have reduced levels of L1 box/ gibberellic acid (GA)-regulated putative targets, including LIP1, LIP2, LTP1, FDH and PDF1, in the presence of GA and during seed germination, thus leading to a delayed germination upon imbibition (PubMed:24989044). In plants missing HDG3, HDG7, HDG11, PDF2 and ATML1, increased cell division leading to cell overproliferation (PubMed:25564655). Belongs to the HD-ZIP homeobox family. Class IV subfamily. Probable cloning artifact leading to a deletion into the sequence.