S01 - Session P6 - WOX4 and PXY regulate phase transition for pluripotent stem cell induction in Arabidopsis and carrot cells

Authors: Jong Eun Han *, So-Young Park, Hyunwoo Cho, Hyeona Hwang

Cambial meristematic cells (CMCs) are rapidly dividing cells and one type of the pluripotent stem cells in plants. In this study, PXY (PHLOEM INTERCALATED WITH XYLEM) and WOX4 (WUSCHEL-RELATED HOMEOBOX4) , which are involved in maintaining the identity of CMCs, were cloned and introduced into Arabidopsis thaliana to identify their function in the plant. After that, these two genes were introduced into carrot cells to investigate whether they are involved in the phase transition from somatic cells to stem cells. The pCB302ES- 35S:DcPXY :GFP and pCB302ES- 35S:DcWOX4 :HA were cloned from the carrot genome and introduced into Agrobacterium tumefaciens (GV3101) by transformation. To confirm their function, DcWOX4 was integrated into col-0 (WT), wox4 mutant, and pxy mutant of A. thaliana . To identify maintenance of cambium stem cells, the transformation was conducted in embryogenic cells (ECs) and non-embryonic cells (NECs) of carrot cells. The 35S:DcWOX4 -HA/col-0 increased the number of secondary xylem cells, confirming that DcWOX4 is involved in the division of cambium cells. In addition, 35S:DcWOX4 -HA/ wox4 , restored the function of cambium cells, confirming the development of secondary xylem cells. These results indicate that DcWOX4 functions are similar to those of AtWOX4 . Based on this, DcWOX4 and DcPXY were introduced into carrot ECs and NECs, and the results showed that these two genes increased cell division, while many molecular markers revealed that they were related to the phase transition from de-differentiation cells to stem cells in carrot cell cultures. These findings revealed that cultured cells could transit, and maintain their physiological phase into stem cells by regulation of these transcription factors, and that is possible to regulate the pluripotent stem cell fate.