From root to embryogenic transition: WOX5 reprograms plant somatic cells via auxin-mediated pathways.

The study was focused on the WUSCHEL-RELATED HOMEOBOX 5 (WOX5), a member of the WUSCHEL family of homeodomain transcription factors, of the root apical meristem (RAM) - specific function in the quiescent center (QC) and columella stem cell maintenance. We revealed that WOX5 is also engaged in the embryogenic transition of plant somatic cells cultured in vitro. We showed that WOX5 controls the induction of somatic embryogenesis (SE) in Arabidopsis. The results suggest that the function of WOX5 in SE induction is related to controlling genes related to diverse auxin-related processes, including biosynthesis, transport, distribution, and signaling of auxin in plant development (TAA1, YUC1, PIN1, LEC2, PLT3, ARF5). The postulated WOX5 targets in embryogenic induction also involve CDF4, controlling cell differentiation in RAM. The study reveals genetic parallels between stem cell maintenance in RAM and in vitro-induced embryogenic transition in somatic cells.The findings identified WOX5 as a new regulatory element within the transcription factor network controlling embryogenic response in somatic plant cells. Identifying embryogenic/pluripotency-related functions of WOX5 opens further opportunities for improving in vitro plant regeneration of recalcitrant species.