This project seeks to learn more about how proteins are expressed from genes in plants. After DNA is transcribed into RNA, the RNA molecules are often further processed before they form messenger RNA, the molecule that specifies the protein that will be synthesized from the instructions that were coded in a gene. One type of RNA processing is RNA editing. In plant chloroplasts, the organelle in plant cells that is responsible for photosynthesis, RNAs transcribed from chloroplast genes are altered by the modifying of one nucleotide ("C") into another ("U"). The change from C to U alters the amino acid encoded by the RNA, and changes the composition of the protein that is made. In chloroplasts, RNA editing is a way to correct mistakes in the genes that would prevent production of functional chloroplast proteins. Plants without proper RNA editing would fail to thrive. RNA editing also occurs in microrganisms and animals, where the process is essential for synthesis of important proteins. Maize chloroplasts are known to undergo 28 different C-to-U editing events. However, none of the enzymes or proteins that carry out chloroplast RNA editing have yet been identified. Furthermore, it is not known why one C is selected for conversion to U, while most Cs remain unaltered. Maize extracts capable of carrying out editing when provided with chloroplast RNAs will be used to study the features of the RNA that are essential for recognition of the proper C target of editing. The maize extracts will also be fractionated in order to learn more about the molecules involved in converting C to U. These studies will take advantage of databases containing maize nuclear and chloroplast genome sequences, maize chloroplast protein sequence data, and maize mutant collections which were generated through projects supported by the NSF. Development of the in vitro editing extract will have a broad impact on the editing community. The project will provide training opportunities at several levels and include participation by underrepresented minorities.
