In eukaryotes, appropriate regulation of gene expression is essential for growth and development.  Transcriptional regulation can modulate expression of a gene from very low to very high levels, and gene silencing refers to a process where transcription of a gene is reduced or abolished. Recent evidence particularly emphasizes the importance of RNA-directed silencing mechanisms in eukaryotes, including maize. Maize is an important crop for industrial and nutritive purposes, and also an excellent model for studying gene silencing. We study gene silencing in maize, which will enhance our ability to use this organism for food and fuel products. According to a model commonly used to explain RNA-directed gene silencing in plants, a specialized RNA polymerase (Pol IV) generates molecules that are processed into small interfering RNAs (siRNAs).  siRNAs interact with homologous transcripts from another RNA polymerase (Pol V) to recruit chromatin modifiers that establish a silent epigenetic state at the regulated locus. This presents an intriguing paradox, because regulation at a locus blocks transcription by some polymerases (Pol II), but requires transcription by others (Pol IV and Pol V). It’s not yet known how this differential access is specified or maintained through cell divisions, nor how a specified locus is designated for silencing. The long term research goal in my lab is to identify the mechanisms by which RNA-directed silencing is initiated and maintained, and how it influences gene expression in the plant.