Growth-Regulating Factors, A Transcription Factor Family Regulating More than Just Plant Growth

The GROWTH-REGULATING FACTOR ( GRF ) family of transcription factors (TFs) is a small gene family found in land plants and is defined by the presence of two highly conserved protein domains: WRC (Trp–Arg–Cys) and QLQ (Gln–Leu–Gln). The WRC domain contains a nuclear localization signal and a zinc (Zn) finger motif involved in DNA binding. The QLQ domain mediates the interaction between GRFs and transcriptional coactivator GRF-INTERACTING FACTORs ( GIFs ), which in turn recruit SWI/SNF chromatin remodeling complexes to modulate transcription. Many GRF transcripts are posttranscriptionally regulated by microRNA miR396. As a result, GRFs usually show their maximum activity in proliferating tissues. In this chapter we summarize not only the role of GRFs in leaf growth, but also more recently discovered functions in reproductive development, senescence, and developmental plasticity in response to external cues.