Regulation of RNA stability plays an important role in gene expression, but the mechanisms involved are poorly understood. This proposal addresses molecular and biochemical factors that regulate differential turnover of higher plant plastid mRNAs during organelle biogenesis. Emphasis is placed on the study of highly conserved inverted repeat (IR) sequences found at the 3' ends of plastid mRNAs. Plastid 3' IRs bind proteins, and act as RNA processing elements and stability determinants in vitro. I propose to investigate whether protein:RNA associations at the IR are involved in the regulation of plastid RNA turnover. These studies will entail mutagenesis of 3' IR sequences, and purification of RNA-binding proteins These proteins will be used in functional assays and to raise antibodies, which will be used to investigate developmental changes in protein concentrations, and eventually in isolation of the genes encoding them. The in vivo structure of plastid mRNAs will be probed by analyzing ribonucleoprotein particles (RNPs) from plastids, and their half lives will be quantified by in vivo labeling. The long-term objectives are to develop a model for the developmental control of plastid mRNA stability, and to determine if nuclear gene products are among the factors that influence plastid mRNA decay.***//
