Plants need to integrate an array of signals to regulate complex patterns of gene expression.This is important since plants have specialized needs to respond to changes in the environment. Regulation of gene expression in plants is important for integration of external signals such as temperature,day length, concentration of di erent metabolites and light quality in the series of events that ultimately lead to owering. Finally, the regulation of gene expression during speci c stages of seed development is an interesting example of tissue and develop- mental control which is of considerable agricultural importance.

Stefan Bjorklund 1150 766bjorklund_1A cartoon of a eukaryotic transcription initiation complex consisting of DNA, TBP, TFIIB, E, F and H, Mediator, Pol II and a specific transcription factor binding to an enhancer element.
In all eukaryotes, protein-encoding genes are transcribed by RNA polymerase II (pol II). To perform its most basal functions; promoter recognition, melting of the DNA template at the transcription start,
formation of the first phosphodiester bonds and promoter escape, pol II requires five so called general transcription factors (GTFs). These GTFs; TBP, TFIIB, E, F, and H are conserved in all eukaryotes and together with pol II they form a preinitiation complex comprising nearly 30 polypeptides. Mediator is a multisubunit complex which functions as a connector between the promoter-bound transcriptional regulators and pol II.
Surprisingly, Mediator had not been identified in plants until we recently succeeded to purify Mediator from A. thaliana through conventional biochemical purification combined with reversed-phase LC-ESI-MS/MS. This was the first description of Mediator in a plant, and it was evident that it required a biochemical approach since most of the A. thaliana Mediator subunits show very low sequence homol- ogy to the corresponding proteins in yeast and metazoans. Plant Mediator is probably structurally conserved, but the amino acid sequences of individual subunits differ considerably when compared to other eukaryotes. Plants also contain a set of unique Mediator subunits, which are likely to be involved in regulation of plant-specific gene expression.

sweden_greySvensk sammanfattning