| Description: | Sometimes transgenes are not properly expressed in plants due to gene silencing. In some of the most interesting examples, transgenes are still transcribed but the resulting RNA is rapidly degraded. How does this mechanism of post transcriptional gene silencing (PTGS) work and why does such a mechanism exist? In order to answer these questions, we propose to compare transcripts from a mutant line actively engaged in PTGS to RNA from the wild type parental line. The egs1 mutation causes consistent post transcriptional silencing of a transgene in seedlings. This is the only gene characterized to date that enhances gene silencing. We propose to compare gene expression in egs1 mutants to expression in the parental wild type genomic background to identify genes (other than the transgene target of PTGS) that are affected when the PTGS mechanism is activated. By comparing transcripts of egs1 mutant seedlings to those from age matched wild type seedlings, we expect to identify genes of several classes: 1. genes regulated by the wild type EGS1 gene product; 2. genes with products that are participants in the PTGS mechanism; and 3. endogenous genes that are targets of PTGS. This last class will answer the question of whether PTGS has a developmental function in addition to its role in controlling expression of introduced genes. PTGS has been predicted to protect plants from overactivity of transposable elements, from infection by RNA viruses and potentially to be involved in development. Because PTGS is enhanced in egs1 mutants, this comparison gives us the opportunity to discover genes that are regulated when the PTGS mechanism is activated. Since egs1 mutants resemble wild type plants when grown in the greenhouse, we cannot predict what kind of genes may be regulated by PTGS. However sensitive gene expression comparisons possible by DNA microarray comparisons are the best available method to reveal as yet unknown targets. Knowing which genes that are up or down regulated when PTGS is active will illuminate the function the PTGS mechanism normally plays in plant gene regulation. |
NASCArrays Information at The BAR
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