The most obvious functions of nucleases are nucleic-acid turnover and phosphate mobilization, but they also have more subtle roles. By its nature, nuclease activity may disrupt cellular information flow. Familiar examples include degradation of specific mRNAs, and bacterial restriction endonucleases. In some plant families, RNases have been recruited for highly specific pollen rejection systems. This chapter reviews methods and protocols used to manipulate plant breeding behavior using these RNases. Here, the “assay” for RNase activity is different from the others described in this volume. In our system, RNases determine mating behavior; thus, the ultimate “assay” is whether or not a fruit is formed following pollination.
