# Stem Cell Factors BAM1 and WOX1 Suppressing Longitudinal Cell Division of Margin Cells Evoked by Low-Concentration Auxin in Young Cotyledon of Arabidopsis

## TL;DR

The paper explores how stem cell factors BAM1 and WOX1 regulate cell division in Arabidopsis cotyledons under low auxin concentrations.

## Contribution

It introduces a new model showing moderate auxin concentration triggers developmental transitions in plant cells.

## Key findings

- Margin cells transition from elongation to elongation and division phases during early seedling growth.
- BAM1 and WOX1 regulate this transition, and their absence prevents auxin-induced cell division.
- Low-concentration auxin promotes longitudinal cell division in cotyledon margin cells.

## Abstract

Highly differentiated tissues and organs play essential biological functions in multicellular organisms. Coordination of organ developmental process with tissue differentiation is necessary to achieve proper development of mature organs, but mechanisms for such coordination are not well understood. We used cotyledon margin cells from Arabidopsis plant as a new model system to investigate cell elongation and cell division during organ growth and found that margin cells endured a developmental phase transition from the “elongation” phase to the “elongation and division” phase at the early stage in germinating seedlings. We also discovered that the stem cell factors BARELY ANY MERISTEM 1 (BAM1) and WUSCHEL-related homeobox1 (WOX1) are involved in the regulation of margin cell developmental phase transition. Furthermore, exogenous auxin treatment (1 nanomolar,nM) promotes cell division, especially longitudinal cell division. This promotion of cell division did not occur in bam1 and wox1 mutants. Based on these findings, we hypothesized a new “moderate auxin concentration” model which emphasizes that a moderate auxin concentration is the key to triggering the developmental transition of meristematic cells.