The goal of this proposal is to define the molecular mechanisms of this posttranscriptional regulation as part of the long-term objective to understand the control of organelle gene expression and the role of the nuclear genome in this process. Dr. Gruissem will examine in detail the function of inverted repeat (IR) sequences at the 3' end on plastid mRNAs. These IR sequences are ubiquitous, their sequences is conserved between evolutionary divergent plants, and they do not act as efficient transcription terminators, but homogeneous plastid mRNA 3` ends are established by processing. Preliminary experiments suggest that proteins bind to the 3` IR sequences, and their abundance changes during plant development are correlated with differential mRNA accumulation. This RNA: protein interaction is of interest, because it may delinaeate a novel regulatory mechanism in the control of plastid gene expression. This work should provide new results to help fill the gap that currently exists in our understanding of posttranslational regulatory mechanisms. Additionally the studies may potentially lead to new insights into the role of the nuclear genome in the control of organelle expression.
