COMPARATIVE STUDIES OF KNOX TRANSCRIPTION FACTORS TO IDENTIFY NOVEL MOLECULAR SIGNATURES IMPORTANT FOR FUNCTIONAL DIVERSIFICATION

Knotted1-like homeobox (KNOX) transcription factors belong to the three amino acid loop extension (TALE) superclass of homeodomain proteins in higher plants. KNOXs play a key role in several developmental processes by maintaining a proper balance between undifferentiated and differentiated cell state through the modulation of multiple hormonal pathways. Besides the homeodomain, KNOX proteins are characterized by the presence of a consensus region called MEINOX that defines this subclass of the TALE family. MEINOX domain is important for protein-protein interactions with a second group of TALE proteins, the BEL-like homeodomain (BLH) family. This interaction modulates KNOX nuclear localization and, likely, target selection. The major goal of our laboratory is to define the molecular mechanisms that underlie KNOX function in cell fate determination and organogenesis using model organisms and transfer the acquired knowledge to non-model plant species including important crops. Our research aims at developing strategies and tools for using KNOX genes, or other components of KNOX developmental pathways, in the selection of plant traits relevant to agriculture production. The traits we are interested in are: leaf morphology and development, vascular differentiation, leaf/stem ratio, lignin content, vegetative-to-reproductive transition, stem architecture, hormone homeostasis, organogenesis, maintenance of indeterminate cell fate, optimization of nitrogen fixation in legumes. Our main research projects regard: post-transcriptional regulation of KNOX1 genes in Arabidopsis thaliana and Medicago truncatula - the role of KNOX1 in the determination of M. truncatula compound leaves - the identification of novel developmental pathways which involve different KNOX transcription factors - the identification of Arabidopsis KNOX functional orthologs in Medicago truncatula for forage legumes, Prunus persica for fruit tree species and Cichorium intybus for cultivated salad species of commercial interest. We will present our latest data on KNOX transcription factors coming from a comparative scientific approach. To gain new insights into the role of alternative splicing in KNOX genes, we will present the functional characterization of a novel isoform of the KNAT1/BP transcription factor (BPhox) that encodes the homeodomain but lacks the MEINOX domain. We will also show data regarding an alternative spliced STM-like gene of M. truncatula (MtKNOX6) that induces novel phenotypes when overexpressed in Arabidopsis thaliana. We will explore the possibility to use the structural polymorphism of KNOX proteins from different species to identify key amino acid residues that are important for functional diversification.