Perianez-Rodriguez, J. | bioRxiv Science

bioRxiv2023

GNOM-Dependent Endosomal Recycling Sets the Timing of Founder Cell Specification

1.Lateral root growth occurs from primed xylem pole pericycle cells that can be specified as founder cells, but how these cells acquire the pluripotency state to initiate a root organogenesis program is not fully understood. Here, we find that the EMS 204 mutant is unable to specify founder cells due to a point mutation affecting the C-terminal HDS3 domain of the GNOM protein. We used genetics and cell biology to study the trafficking machinery of xylem pole pericycle cells, cells in which GNOM is primarily associated with recycling endosomes. We found that the lack of the HDS3 domain negatively affects the stability of the GNOM protein within the cells of the xylem pole pericycle and, subsequently, the integrity of the trafficking machinery of these cells. We determined that GNOM is responsible for the recycling of AUX1 toward the plasma membrane at the xylem pole pericycle and impairment of this recycling results in premature accumulation of AUX1 in the vacuole. In this work, we describe a cell type-specific cellular mechanism and the role of a particular domain during lateral root development.

plant biology↗

bioRxiv2019

Stem Cell Activity And Regeneration In Roots Require Non-Cell Autonomous Regulation From The Ground Tissue

Stem cells are central to plant development. During root postembryonic development stem cells generating tissues are patterned in layers around a stem cell organizer or quiescent center (QC). How stem cell lineages are initially patterned is unclear. Here, we describe a role for BLUEJAY (BLJ), JACKDAW (JKD) and SCARECROW (SCR) transcription factors in patterning of cell lineages during growth and in patterning reestablishment during regeneration through regulation of number of QC cells and their regenerative capacities. In blj jkd scr mutants, QC cells are progressively lost which results in loss of tissue layers. Upon laser ablation blj jkd scr is impaired in QC division and specification resulting in severe impairment in pattern regeneration. Beyond direct regulation of QC activity by these transcription factors, reduced levels of SHORT-ROOT (SHR) and of PIN auxin transporters were observed in the vasculature of blj jkd scr, leading to strong reduction in the auxin response in the QC. We narrowed down non-cell-autonomous regulation of vascularly expressed genes in blj jkd scr to C-REPEAT BINDING FACTOR 3 (CBF3). cbf3 mutant shows reduced levels of SHR in the vasculature, and in addition QC disorganization and downregulation of the QC regulator WUSCHEL-RELATED HOMEODOMAIN 5 (WOX5). CBF3 gene is primarily expressed in the ground tissue downstream of BLJ, JKD and SCR, while CBF3 protein may move. Targeted-expression of CBF3 to the ground tissue of blj jkd scr recovers radial patterning and regeneration. We propose that BLJ, JKD and SCR regulate QC-mediated patterning, and that part of this regulation involves CBF3.

developmental biology↗