CONICET | Buscador de Institutos y Recursos Humanos

While plant leaves grow in a defined fashion, its roots grow indeterminately through the meristem. This micro-environment that has active cell proliferation capabilities but limited cell differentiation is present both in plant roots and stem. Several regulatory networks have been associated with the maintenance of the meristems; among them, we focused our studies on the transcription factors that belong to the GROWTH-REGULATING FACTOR (GRF) family. Arabidopsis thaliana GRF family is composed of nine different members, among which seven of them are post-transcriptionally repressed by microRNA miR396. GRFs have two highly conserved domains: on the one hand the QLQ domain is responsible for its interaction with other proteins, and on the other hand, the WRC domain, which has a nuclear localization signal, is necessary for DNA binding. According to previous results from our and other groups, GRF interacts in vivo with a transcriptional co-regulator called GRF-INTERACTING FACTOR 1 (GIF1). GIF1, in turn, can also interact with BRAHMA, a central component of chromatin remodeling complexes. In this work, we studied the role of GRF/GIF interaction in cell proliferation and root meristem identity. First, we generated inducible lines for both genes that could complement each mutation. These lines were used for RNAseq transcriptomic analysis that allowed us to study genes regulated by GRF3 and GIF1. Common genes regulated by both proteins included PLETHORA1 and 2, which encode transcription factors that function as master regulators of the root. Then, we explored the interaction at a protein level on the stable inducible lines and also on transient infiltrated Nicotiana benthamiana leaves. The results obtained allowed us to propose a model for the function of the GRF/GIF network that might be relevant for varieties of agronomical interest.