| Description: | Plant organs have a limited lifespan, and senescing organs have a very different profile of gene expression than immature or mature organs. We are interested in the transition between the non-senescent and senescent state. What happens at the onset of senescence? Is the transition abrupt or gradual? Does it involve large global changes, upregulation (or downregulation) of selected suites of genes, or relatively small changes initially? To address these questions, we will take advantage of the unique floral phenotype associated with overexpression of the MADS domain factor AGL15. Plants that overexpress AGL15 show delayed senescence, as well as delayed abscission, of the outermost whorls of floral organs (Plant Cell 12: 183-197, 2000). By comparing RNA populations in mature wild type flowers and mature flowers of AGL15 overexpressors, we can examine how gene expression patterns change during the transition between states and identify sequences whose expression increases (or decreases) just as the senescence programs start to unfold. To ensure that the samples we are comparing are as similar developmentally as possible, we will grow wild type plants and plants carrying a CaMV 35S: AGL15 transgene (both in WS background) side-by-side under highly controlled conditions in a growth chamber. At four days after the start of flowering, we will collect samples for RNA preparation. In wild type, the programs that drive tissue senescence appear to be activated soon after flowers open. We will collect the youngest open flower, the bud immediately above it, and the two flowers immediately below it from both sets of plants. RNA will be prepared from the pooled bud/flower samples to give us one wild type (pre-senescent) sample and one AGL15 (non-senescent) sample for microarray analysis. Most studies of senescence processes have involved comparisons between organs of different ages. The advantage of the approach we outline here is that age is no longer an experimental variable: the two samples will be developmentally equivalent in nearly every regard. Through this analysis, we expect to identify molecular events associated with the onset of senescence processes in plant tissues and learn how AGL15 overexpression affects global expression patterns during an important developmental transition. |
NASCArrays Information at The BAR
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