RT Journal Article SR Electronic T1 An Arabidopsis AT-hook motif nuclear protein mediates somatic embryogenesis and coinciding genome duplication JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.01.03.892869 DO 10.1101/2020.01.03.892869 A1 Omid Karami A1 Arezoo Rahimi A1 Patrick Mak A1 Anneke Horstman A1 Kim Boutilier A1 Monique Compier A1 Bert van der Zaal A1 Remko Offringa YR 2020 UL http://biorxiv.org/content/early/2020/01/03/2020.01.03.892869.abstract AB Plant somatic cells can be reprogrammed to totipotent embryonic cells that are able to form differentiated embryos in a process called somatic embryogenesis (SE), by hormone treatment or through overexpression of certain transcription factor genes, such as BABY BOOM (BBM). Here we show that overexpression of the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED 15 (AHL15) gene induces formation of somatic embryos on Arabidopsis thaliana seedlings in the absence of hormone treatment. During zygotic embryogenesis, AHL15 expression starts early in embryo development, and AH15 and other AHL genes are required for proper embryo patterning and development beyond the heart stage. Moreover, AHL15 and several of its homologs are upregulated and required for SE induction upon hormone treatment, and they are required for efficient BBM-induced SE as downstream targets of BBM. A significant number of plants derived from AHL15 overexpression-induced somatic embryos are polyploid. Polyploidisation occurs by endomitosis specifically during the initiation of SE, assumingly due to AHL15-mediated heterochromatin decondensation coinciding with the acquisition of embryonic competency in somatic plant cells.