Intellectual Merit. RNA editing modifies specific cytidines in angiosperm chloroplast transcripts to uridine. C-to-U editing is thought to function to correct detrimental T-to-C mutations in the chloroplast genome. Evolutionary processes have shaped the occurrence and molecular mechanism of RNA editing in chloroplasts since the phenomenon arose in an ancestor to extant seed plants. Genomic information available from Arabidopsis thaliana will provide a foundation for a phylogenetic analysis of chloroplast targets of editing and the members of the large nuclear-encoded pentatricopeptide motif-containing protein family that are required for editing site conversion. Additional editing factors will be identified in A. thaliana to gain a more comprehensive picture of the nuclear-encoded machinery devoted to chloroplast RNA editing. C-to-U editing events in members of the Brassicaceae will be identified for comparison to those occurring in A. thaliana. The loss and acquisition of C targets as well as nucleotide changes in the sequences surrounding them will be traced within the Brassicaceae. Sequences of three editing trans-factors will be analyzed in detail to understand how the rapidly evolving nuclear genes coevolve with the more slowly evolving chloroplast genes. Knowledge of nucleotide diversity in both the RNA editing targets and the corresponding trans-acting proteins will be used for functional tests of the consequences of evolutionary change in nuclear proteins and editing of chloroplast RNAs.
Broader Impacts. Efficient capture of solar energy by chloroplasts is essential for optimal plant growth to provide biomass and other agricultural products. The project will provide fundamental information about an important molecular mechanism that corrects defects in the chloroplast genome that would otherwise impair photosynthetic activity. The project will provide multidisciplinary training for postdoctoral associates and a graduate student and 10-12 undergraduates at both Cornell University and University of California-Irvine (UCI). Topics related to project content will be developed by the co-P.I. and NSF GK-12 graduate student participants at UCI. Materials will be developed that K-12 classroom teachers will be able to implement in grade 7, 9 or AP biology classrooms and will be available through the UCI GK-12 web site (http://port.bio.uci.edu/NSF-GK-12/default.htm). The P.I. will assist the Cornell Institute for Biology Teachers in incorporating these materials into the comparable workshops that are periodically held at Cornell for K-12 teacher training.
