Methodical manual on the implementation of the course project on discipline "Technological preparation of production" for students of all forms of study Direction of preparation 131 " Applied mechanics"

Abstract

The regulation of C4-specific genes is influenced by many internal and external stimuli that are easily manipulated. Thus, C4-genes are good candidates to investigate signal integration on the chromatin level. Recent studies that focused on the C4-specific Pepc-gene revealed a complex promoter regulation due to histonmethylation and -acetylation influenced by specific stimuli. Recent results for the C4-specific Pepc-gene revealed that specific histone acetylation and methylation sites are controlled by specific stimuli and that this contributes to a complex promoter regulation. In this study it became evident that the C4-Me-gene as well as eight additional analyzed genes show tissue specific trimethylation of H3K4 as shown before for the C4-Pepc-gene. This modification is neither influenced by transcription nor by light. Extensive studies of different tissues also verified that H3K4me3 is etablished only in the tissue of leaves where the genes can be later activated by light. Moreover, analysis of embryonic callus cultures revealed that H3K4 trimethylation is induced during the process of cell differentiation. To enable such comarison of chromatin from different tissues in ChIP-analyses, a new method was developed. The presented data indicate that H3K4 trimethylation is a mark for tissue-specific expression of genes in leaves of maize and the establishment of this modification is influenced by a tissue-specific signal. The comparison of leaf tissues also revealed a tissue-specific histone acetylation of the C4-Pepc-promoter. This applies exclusively for the distal, but not the proximal promoter region. Again, this pattern is established independent of transcription of the gene. In the last part of the thesis, allele-specific epigenetic modifications were investigated. By this, an explanation for the earlier described repressive epigenetic marks (H3K9me2 and DNA-methylation) on the active Pepc-gene was identified: The maize genome harbours multiple copies of pseudo-C4-Pepc-genes. Unlike the active C4-Pepc-gene, these inactive copies are labeled by repressive modifications. Furthermore, significant differences in gene activity were found between the two Pepc-alleles of a hybrid maize line. However, these transcriptional differences are not caused by differences in histone acetylation. These results expand our knowledge about the role of chromatin in signal integration in plants