| Description: | Genes upregulated by stress provide insight into physiological changes that enable plant adaptation to diverse environments. An unusual set of genes, the Arabidopsis TCH genes, are upregulated in response to mechanical stimuli (Braam and Davis, 1990). However, darkness, temperature shocks, auxin and brassinosteroids also induce TCH expression. The characterized TCH regulatory regions lack canonical cold, heat and auxin cis-elements; thus, we hypothesize (Braam 2000) that these stimuli act directly to regulate some genes (e.g., COR, HSP, IAA/Aux) and indirectly for others (e.g., TCH) by causing mechanical perturbations.Our first proposed microarray experiments will be to determine and compare profiles of genes upregulated 30 min after touch and darkness. Perception of these stimuli is likely to occur through distinct mechanisms and yet both lead to rapid and strong TCH expression. The calmodulin-related and xyloglucan endotransglycosylase TCH proteins are proposed to function collaboratively in modifying cell walls and turgor at sites of mechanical stress (in response to touch) and cell expansion (in response to darkness) (Braam et al., 1997; Campbell and Braam 1999). A global view of the genes upregulated under these conditions will shed light on these fundamental cellular processes. The functions of the genes will be investigated using insertional mutagenesis and inducible RNAi expression methods ongoing in the lab to dissect TCH gene function.We will employ 2 slides to identify touch-inducible genes and 4 slides for darkness-inducible genes. The Davis lab has a (2-slide) duplicate experiment planned to identify touch-inducible genes; our 2-slides will provide 4-fold replication to verify our combined results. We will employ the Davis lab protocol (aerial portion of 3.5-week-old Columbia). Each replicate (untreated and treated) will be performed on identical age plants at different times of day on different days to enhance reliability of the results. We will also take advantage of available microarray data that profile genes induced by hormones (IAA and BR) and temperature shifts. We expect that genes related to the TCH genes in regulatory and functional properties will be induced by all the stimuli. The TCH genes will be positive controls if available on slides, or alternatively on northerns of RNAs to be requested from labs performing related microarrays. |
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