Overexpression of Peony PoWOX1 Promotes Callus Induction and Root Development in Arabidopsis thaliana

Plant-specific WUSCHEL (WUS)-related homeobox (WOX) family of transcription factors are involved in apical meristem maintenance, embryogenesis, lateral organ development, and hormone signaling. Among the members of this family, WOX1 is known to play essential roles in many species. However, the function of the peony 'Feng Dan' (<i>Paeonia ostii</i> L.) <i>WOX1</i> (<i>PoWOX1</i>) remains unknown. The initial bioinformatic analysis revealed that <i>PoWOX1</i> belongs to the modern clade of the <i>WOX</i> gene family and has a highly conserved homeodomain (HD), the WUS motif, the STF-box, and the MAEWEST/WOX4-box. Subsequent heterologous overexpression in <i>Arabidopsis thaliana</i> revealed that <i>PoWOX1</i> promotes root growth, early shoot initiation, and flowering. The root vascular tissues, especially the arrangement and size of xylem cells, were different between the <i>PoWOX1</i>-overexpressing transgenics and the wild-type plants, and the pericycle cells adjacent to the xylem divided more easily in the transgenics than in the wild type. Furthermore, under in vitro conditions, the transgenic leaf explants exhibited more callus induction and differentiation than the wild-type leaf explants. Thus, the study's findings provide novel insights into the role of <i>PoWOX1</i> in promoting root development and callus tissue induction and differentiation, serving as a reference for developing an efficient regeneration system for the peony.