GIF transcriptional coregulators control root meristem homeostasis ($)

Transcription factor GRFs (GROWTH-REGULATING FACTOR) are specifically expressed in TACs (transit-amplifying cells) and promote rapid cell divisions. Their expression is repressed in stem cells through miR396. In this work, they studied the functions of small cofactors known as GIFs (GRF-INTERACTING FACTORs) for maintaining meristem size and root development. Arabidopsis has three members (GIF1/AN3, GIF2, and GIF3) of this group and their corresponding mutants demonstrate distorted QC (quiescent center) and longer root meristem. As a mechanistic explanation, they have found that AN3/GIF1 binds directly to the promoter region of PLT1 (PLETHORA1) and SCR (SCARECROW) to regulate their expression. Among them, SCR is involved in positioning of the SCN (stem cell niche) and the PLT gradient that determines the root domains. Taken together, this study suggests that GIFs participate in multiple pathways to control QC organization and meristem size. (Summary by Arif Ashraf@aribidopsis) The Plant Cell 10.1105/tpc.17.00856