The PIRL genes are a family of nine genes discovered during the sequencing of the Arabidopsis thaliana genome, the first fully-sequenced plant genome. PIRLs are a previously uncharacterized class of plant leucine-rich repeat (LRR) proteins that are hypothesized to be important to plant development. As part of an ongoing systematic study to gain insight into PIRL functions, I examined Arabidopsis plants engineered to overexpress the PIRL9 gene. Plants containing an extra copy of PIRL9 designed to drive overexpression of the gene were identified and observed as they grew. Abnormal leaves were observed in most of these plants and stunted growth was quantified through measurements of leaf length and width, as well as primary stem height. Using qPCR, the amount of PIRL9 mRNA present in the different plants was quantified and linked to previous plant measurements. Data showed a correlation between severely stunted plant growth and overexpression of the PIRL9 gene. Significance of these results for PIRL9 function will be discussed, but further genetic and phenotypic analysis is needed to confirm and assess the effects of PIRL9 overexpression. 

Currently there are three major classes of known viruses: exclusively RNA viruses, which do not require a DNA intermediate in their replication and propagation; DNA viruses, which use DNA dependent processes to perform their genome replication; so-called retroviruses, which go through both an RNA and a DNA phase with the help of a reverse transcriptase enzyme. Until very recently there was no evidence that there was genetic exchange between these distinct virus classes. However, a single stranded DNA (ssDNA) virus genome, recently found using metagenomics in Boiling Springs Lake in Lassen Volcanic National Park, USA (BSL) contains elements homologous to both ssRNA and ssDNA viruses. The genome of this RNA-DNA hybrid virus (BSL-RDHV) contains a gene similar to that of ssDNA circoviruses that infect animals and a capsid protein (CP) gene similar to that of the ssRNA tombusviruses that infect plants. It is currently unclear how the RNA virus capsid gene integrated into the DNA virus genome and what, if any, evolutionary impacts are associated with this recombination. My current work focuses on the characterization of the BSL-RDHV CP using recombinantly expressed protein. The CP gene will be amplified from the BSL viral metagenome using Polymerase Chain Reaction and expressed in bacterial cells. The long term goal is to determine the structure of this protein using X-ray crystallography and use the protein for in vitro assembly reactions. Successful completion of this work will be an important step towards understanding virus evolution and possibly the emergence of novel virus disease.