TABLE 1.

Transcription factor (TFs) in RAM maintenance.

Name	Class/type	Expression domain	Function	Mobile	Interaction	Reference
WOX5	Homeodomain	QC	Maintains surrounding stem cells; represses QC divisions	Yes		Sarkar et al. (2007), Forzani et al. (2014), Pi et al. (2015)
PLT1-4	AP2/ERF	RAM, mainly QC	Necessary and sufficient for RAM maintenance	Yes (PLT2)		Aida et al. (2004), Galinha et al. (2007)
SHR	GRAS	Stele	QC fate specification and maintenance, asymmetric cell divisions, cortex, and endodermis specification	yes	SCR SIEL JKD MGP BIB	Di Laurenzio et al. (1996), Helariutta et al. (2000), Wysocka-Diller et al. (2000), Nakajima et al. (2001), Welch et al. (2007), Long et al. (2015b)
SCR	GRAS	QC, CEI, endodermis	QC fate specification and maintenance; asymmetric cell divisions, cortex, and endodermis specification		SHR JKD MGP BIB	Scheres et al. (1995), Di Laurenzio et al. (1996), Sabatini et al. (2003), Welch et al. (2007), Long et al. (2015b)
SPT	bHLH	Epidermal initial and CSC, stele	Regulates RAM size and QC cell number		ALC IND	Groszmann et al. (2010), Girin et al. (2011), Makkena and Lamb (2013)
TMO7	bHLH	Adjacent to hypophysis	Embryonic root initiation	Yes	SIEL	Schlereth et al. (2010)
MYC2	bHLH	Ground tissue, vasculature, epidermis, LRC	JA-mediated inhibition of root growth and meristem development; repressing PLT expression			Boter et al. (2004), Chini et al. (2007), Chen et al. (2011), Fernández-Calvo et al. (2011)
UPB1	bHLH	LRC, vasculature	Modulates the balance between cell proliferation and differentiation by controlling ROS production	Yes		Tsukagoshi et al. (2010)
NTT	Zinc finger	Hypophysis and lens-shaped cell (embryo); QC, CEI, CSC, CC	Initiation of the root meristem; confers CSC fate			Crawford et al. (2015)
BRX	BRX family	Vasculature	Regulates RAM size by mediating BR and auxin signaling	Yes	NGA1	Mouchel et al. (2004, 2006a,b), Scacchi et al. (2009)
FEZ	NAC-domain	CSC and LRC/epidermis stem cells	Stimulates periclinal divisions in the LRC/epidermis initials and CSCs			Willemsen et al. (2008), Bennett et al. (2010, 2014)
SMB	NAC-domain	Maturing root cap cells	Constrains CSC-like activity and promotes differentiation; activation of root cap maturation together with BRN1&2			Willemsen et al. (2008), Bennett et al. (2010, 2014), Fendrych et al. (2014)
BRAVO	R2R3-MYB	QC, vascular initials, CEI	Repressor of QC divisions; counteracting BR signaling		BES1	Vilarrasa-Blasi et al. (2014)
BES1	BZR1-like	RAM	Activates QC divisions; represses BRAVO		BRAVO	Vilarrasa-Blasi et al. (2014)
ERF115	ERF	Dividing QC cells	Regulates QC divisions			Heyman et al. (2013)

Summary of the function, interaction, and mobility of key TFs involved in RAM development and maintenance.