Abstract
Here, Shimotohno et al. investigated how upstream factors that regulate WUS and WOX genes converge to position organizer cells during embryogenesis, initiation of new lateral organs, and regeneration after tissue damage in
Arabodopsis
. Here, they show that PLT and SCR genes genetically and physically interact with plant-specific teosinte-branched cycloidea PCNA (TCP) transcription factors to specify the stem cell niche during embryogenesis and maintain organizer cells post-embryonically.
Continuous formation of somatic tissues in plants requires functional stem cell niches where undifferentiated cells are maintained. In
Arabidopsis thaliana
,
PLETHORA
(
PLT
) and
SCARECROW
(
SCR
) genes are outputs of apical–basal and radial patterning systems, and both are required for root stem cell specification and maintenance. The
WUSCHEL-RELATED HOMEOBOX 5
(
WOX5
) gene is specifically expressed in and required for functions of a small group of root stem cell organizer cells, also called the quiescent center (QC). PLT and SCR are required for QC function, and their expression overlaps in the QC; however, how they specify the organizer has remained unknown. We show that PLT and SCR genetically and physically interact with plant-specific teosinte-branched cycloidea PCNA (TCP) transcription factors to specify the stem cell niche during embryogenesis and maintain organizer cells post-embryonically. PLT–TCP–SCR complexes converge on PLT-binding sites in the
WOX5
promoter to induce expression.