Patricia Leon Mejia, Ph.D.

Research

My research group has been interested in two main lines. One is to understand the molecular events involved during the chloroplast differentiation process and the other relates with the mechanism(s) of sugar sensing and signaling and how this regulation impacts plant development. To accomplish these goals we have used mainly Arabidopsis thaliana as a plant model and a combination of genetic, molecular, biochemical cellular and genomic approaches. 1.- Molecular events involved during the chloroplast differentiation process The biogenesis of the chloroplast is a complex mechanism that it is not well understood. The identification of the elements required in this process will permit to advance in our understanding of this fundamental biological process and also will open an avenue for the future manipulation of this organelle. Using genetic approaches we have identified various mutants that block chloroplast development at different stages. Our work with these mutants has contributed to the identification of genes required in a novel biosynthetic pathway involved in the synthesis of plastidic isoprenoids (MEP). Our studies permitted to identify one of the limiting enzymes of this pathway and uncovered some of the mechanisms that regulate this central pathway. These contributions are relevant for future manipulations of the pathway. More recently the characterization of additional mutants altered in chloroplast biogenesis (clb) permitted to highlight novel mechanisms that permit the correct organelle development and its integration to the cellular functionality. These include the production of regulatory signlas and important post-transcritptional regulatory events. Identify the molecules involved in these process and the detailed molecular mechanisms involved in these regulation are our current interest. 2.- Sugar sensing and signaling in plants Glucose acts as hormone-like molecule that modulates central metabolic and developmental processes in plants. The fundamental role that sugar signaling has to plant survival is clear, as it coordinates sugar production, transport, utilization, and storage. The central contribution of glucose signaling is also reflected in the number of genes regulated by this sugar. Glucose signaling is an example that the simplistic idea of a linear transduction pathway for regulating complex processes must change. With the analysis and detailed characterization of mutants affected in sugar responses (gin5, gin6, gin9) we have uncover the close connection between sugar and ABA signaling pathways. Our work provided initial evidences of the complexity underlying sugar signaling and its close connection of the ABA hormone. In addition, our work permit to identify key elements for the sugar signaling cascade in plants such as the transcriptional factor ABI4. The precise role of these factors and the identification of additional molecules in this signaling pathway will give advance in our understanding and in the integration of metabolism, and it represents a challenge that requires multidisciplinary approaches.