After 19 rewarding years at Washington University in St. Louis, the Pikaard lab relocated in 2009 to Indiana University in Bloomington, Indiana. At IU, Craig is the Carlos O. Miller Professor of Plant Growth and Development, with joint appointments in the Department of Biology and the Department of Molecular and Cellular Biochemistry.

In the Pikaard lab, we study the ways in which genes are activated and repressed, using techniques of genetics, genomics, biochemistry, cell biology and molecular biology. Our current research projects are focused on the roles played by chromatin modifying enzymes and noncoding RNAs in gene silencing and epigenetic phenomena. Our favorite epigenetic phenomenon is nucleolar dominance. This phenomenon occurs in genetic hybrids and describes the transcription by RNA polymerase I of ribosomal RNA genes inherited from only one of the progenitors. We have shown that the molecular basis for nucleolar dominance is the selective silencing of one parental set of rRNA genes. Nucleolar dominance operates on a scale of millions of basepairs of chromosomal DNA. In scope, it is second only to the inactivation of one X-chromosome that occurs in the somatic cells of female mammals - the molecular basis for the random splotches of different colors in the coats of calico cats. However, unlike X-inactivation, the choice of which set of rRNA genes to silence is not random, nor is it dictated by a maternal or paternal imprint.

The second focus of the lab concerns RNA polymerases IV and V (formerly Pol IVa and Pol IVb) and their roles in RNA-directed DNA methylation. Pol IV and Pol V are plant-specific polymerases that localize in the nucleus. We have shown that both enzymes have subunit compositions that reveal them to be specialized forms of DNA-dependent RNA polymerase II. Pol IV is required for the production of 24 nt small interfering RNAs (siRNAs) that direct the silencing of repeated sequences in the genome via DNA methylation. Pol V facilitates siRNA mediated silencing by generating transcripts at the target loci to be silenced. Our working hypothesis is that Pol V transcripts serve as scaffolds for the binding of siRNAs associated with the protein ARGONAUTE4, thereby recruiting silencing complexes to the target genes.

Where we are located: The Pikaard laboratory is located in the Biology Department at Indiana University, in Myers Hall Room 300. Craig's offices are in Myers 300B and in 205B Simon Hall, where the Department of Molecular and Cellular Biochemisty is centered.

Our Funding: Our work is supported by grants from the National Institutes of Health, National Science Foundation and the Monsanto Company. Any materials or opinions expressed at this site are those of the author(s) and do not necessaily reflect the views of our sponsors.