R. Michael Mulligan

Ph.D., Michigan State University, 1983
RNA editing in plant mitochondria and chloroplasts
Email address: rmmullig@uci.edu

Plant mitochondrial and chloroplast-encoded mRNAs undergo an editing process in which cytidine residues are converted to uridines. C to U editing is a post-transcriptional processing event that occurs by a site-specific deamination reaction. The C to U changes occur frequently in the protein-coding sequences of organelle-encoded transcripts, and typically cause changes in the amino acid specified by a codon. Edited transcripts encode the evolutionarily conserved amino acid sequence; however, the deduced amino acid sequence from an unedited sequence usually predicts radical amino acid substitutions. Unedited transcripts would direct the translation of "mutant" polypeptides with aberrant amino acid substitutions within highly conserved regions. Thus, RNA editing is required for the expression of the correct genetic information, and serves a genetic function. My lab has recently shown that incompletely edited transcripts are translated. Thus, inefficiency in the editing process results in incompletely edited transcripts, and translation of these mRNAs results in polymorphic gene expression. How translation of incompletely edited transcripts affects organelle biogenesis is currently studied in my lab. Mechanistic studies are aimed at elucidating the nature and specificity of the editing apparatus. In addition, we are developing a molecular genetic approach to identify genes from mutagenized plants that are responsible for RNA editing.

Selected Publications
Phreaner, C.G., Williams, M.W., and R. M. Mulligan. (1996) Incomplete Editing of rps12 Transcripts Results in the Synthesis of Polymorphic Polypeptides in Plant Mitochondria. The Plant Cell 8:107-117

Lu, B., Wilson, R.K., Phreaner, C.G., Mulligan, R.M., and M.R. Hanson. (1996) Protein Polymorphism Generated by Differential RNA Editing of a Plant Mitochondrial rps12 Gene. Molecular and Cellular Biology 16: 1543 - 1549.

Williams, M.A., Kutcher, B.M., and R. Michael Mulligan (1998) Editing site recognition in plant mitochondria: the importance of 5' flanking sequences. Plant Molecular Biology 36:229-237.