Ribonuclease P is an endoribonuclease responsible for the removal of 5’ leader sequences from transfer RNA precursors. Naturally occurring ribozymes, such as RNase P, have been adapted adroitly to cleave specific mRNAs by genetic engineering of either the ribozymes or their substrates. Several recent studies have validated the use of an RNase P-based approach to control gene expression. For instance, RNase P-mediated degradation of viral mRNAs has been used successfully to inhibit influenza virus replication in cell culture. Similar possibilities using endogenous RNase P in plant cells remain unexplored largely due to our poor understanding of plant RNase P. Therefore, in the present investigation, plant RNase P activity was partially purified from Pusa Basmati-1 rice and Black Mexican Sweet maize calli by anion exchange chromatography and glycerol or CsCl density gradient fractionation. The partially purified enzymes from rice and maize efficiently cleave precursor tRNAs derived from plants and cyanobacteria. Examination of the minimal substrate recognition properties of plant RNase P revealed that a plant RNase P-based gene knockout procedure can be included in the repertoire of approaches available for controlling gene expression in plants. Studies are in progress to test the potential of the RNase P-based method for targeted cleavage of mRNAs in suspension cultures of plant cells as well as in transgenic plants.