Within the cell nucleus, the genomic DNA of eukaryotic organisms is packaged into a nucleoprotein complex termed chromatin. This packaging of the DNA has severe consequences for gene expression, and is used as a means of regulating the transcription of genes. The accessibility of the DNA is under control of a wide variety of proteins that are associated with chromatin. Among these proteins are the so-called high mobility group (HMG) proteins. They comprise a heterogeneous family of small and highly-charged proteins that as architectural factors contribute to various DNA-dependent processes including transcription. There is a wealth of biochemical data on members of this protein family, but their in vivo role is still ill-defined. Using the Arabidopsis plant model system, we intend to study the consequences of altered expression levels of HMG proteins. Plants with altered expression of HMG proteins (up- or down-regulated) will be examined in comparison to control plants for possible phenotypic differences as well as their response to environmental cues. Moreover, the transcript profile of these plants is comparatively analysed to reveal possible functional specialisation of different HMG-type proteins. To identify direct links between differentially expressed genes and the HMG protein in question, possible target genes of HMG proteins are also examined for physical association with the respective HMG protein. In summary, these experiments will provide insight into the biological role of HMG proteins, in particular regarding their influence on plant development and their role in gene transcription.
