Identification of plant-specific components of the Polycomb Group pathway and their roles in the regulation of Arabidopsis thaliana development

Abstract

The knowledge about Arabidopsis thaliana developmental life cycle is deep in broad strokes. Nevertheless, the mechanisms that fine tune these phase transitions are still poorly described. One of these mechanisms is the epigenetics, that consist in the precise temporal and -spacial control of genes to respond to specific endogenous or exogenous cues. This control is mediated by different players of diverse nature that together or antagonistically produce a transcriptional change in one or more genes.

In this research project I partially characterized FORGETTER 1 (FGT1) and UBIQUITIN PROTEASE 5 (UBP5), both partners of PWWP-DOMAIN INTERACTOR OF POLYCOMBS 1 (PWO1) a Polycomb Group (PcG) pathway member involved in the maintenance of nuclear morphology and necessary for the repression of some PcG target genes. FGT1 and UBP5 physically interact with subunits of PRC2 and a subunit of the Histone Deacetylase Complex 6. In addition, I demonstrated how FGT1 and UBP5 are necessary for Arabidopsis thaliana development. Specifically, FGT1 is involved in the repression of FLOWERING LOCUS C (FLC), the main floral repressor, suggesting a novel role of FGT1 in inducing flowering, one of the main developmental traits. On the other hand, in the absence of a functional UBP5 the plant displays a pleotropic phenotype, such as loss of shoot apical dominance, delay in germination and delay in flowering. These results suggest that both proteins play an important role in Arabidopsis development.

Taking together, this research will contribute to depict the developmental epigenetic regulation of Arabidopsis thaliana and increase our knowledge in the complex network of proteins that operates within the context of the chromatin regulation.