Research Focus
Dr. Bentolila’s research is aimed at understanding the nuclear control of plant organelle gene expression. Once free-living prokaryotic organisms, the ancestors of mitochondria and chloroplasts were taken up as endosymbionts first by the ancestral cells of eukaryotes and later on by the ancestral cells of the green lineage of eukaryotes. As a result, gene expression and more specifically RNA metabolism in plant organelles is complex and combines bacterial-like traits with novel features that evolved in the host cell. These complex RNA processes are regulated by families of nucleus-encoded RNA-binding proteins.
One model of mitochondrial gene expression under nucleus control concerns pollen development and was extensively studied by Dr. Bentolila when he joined the Hanson lab as a postdoctoral associate. Cytoplasmic male sterility (CMS) is a phenotypic trait encoded by the mitochondrion which results in the inability of the plant to produce viable pollen. Natural suppressors of CMS called restorers of fertility (Rf) are found in the nucleus and have the ability to restore the production of pollen to plants carrying the deleterious mitochondrial CMS associated gene. Cloning of the first Rf gene identified it as a member of the pentatricopeptide repeat (PPR) proteins, a family of helical-repeat RNA-binding proteins, particularly prevalent in plants.
Recently, Dr. Bentolila has focused on RNA editing, a process that modifies cytidines encoded by genomic DNAs to uridines in plant organelle transcripts. A combinatorial approach involving quantitative genetics, biochemistry and genomics allowed identification of several components of the editosome, the editing machinery responsible for the modification of C to U on organelle transcripts. Pentatricopeptide repeat-containing proteins serve as recognition factors for the proper C to undergo editing. However, additional proteins are needed in the editing complex, and Dr. Bentolila’s work has been instrumental in identifying three additional protein families whose members are present in editing complexes in chloroplasts and/or mitochondria. Integration of next generation sequencing technology in the current research has facilitated the characterization of these new families of plant editing factors. Ultimately, the goal of this research is to reconstitute the plant editosome in vitro, which could pave the way for future genetic engineering of RNAs in plants and other organisms, technology which could benefit the biotechnology industry and society.