Characterization of mRNA processing and transcript stability in mitochondria of higher plants
FacultiesFakultät für Naturwissenschaften
LicenseStandard (Fassung vom 03.05.2003)
The mechanisms controlling the expression of the genetic information of plant mitochondria are important components of the total cellular regulatory network. In recent years it has become apparent that beside the level of transcription initiation posttranscriptional processes play a substantial role in the regulation of mitochondrial genes. An important role in RNA stability has been attributed to 3' terminal stem loop structures. In prokaryotes a RNA helicase resolves such stem-loop structures and thus plays a decisive role in the regulation of mRNA stability. Database analyses revealed a RNA helicase from Arabidopsis thaliana. In my thesis research I demonstrated that the nuclear-encoded DExH box RNA helicase (AtSUV3) is located in Arabidopsis thaliana mitochondria and the AtSUV3 mRNA of about 2500 nt is assembled from 16 exons of a weakly expressed unique gene. To determine the influence of posttranscriptional modifications on 3' end processing and mRNA stability in plant mitochondria, pea atp9 and Oenothera atp1 transcripts were investigated for the presence and function of 3' non-encoded nucleotides. My analyses showed that polyadenylation can generally destabilize mRNAs, but the degradation promoting effect is almost annihilated by stabilizing stem-loop structures. Together these antagonistic actions result in the efficient formation of 3' processed and stable transcripts. The characterization of the pea atp9 and Oenothera atp1 transcript termini identified 5' to 3' end connected molecules. The biological function of these head to tail connected RNA molecules in plant mitochondria is unclear. To gain a more general insight into mRNA processing in plant mitochondria, the 5' and 3' extremities of the previously characterized pea cox2 gene were analyzed exemplarily by a new experimental approach based on the in vitro circularization of the respective RNA molecules by T4 RNA ligase followed by a RT-PCR analysis.
Subject HeadingsMessenger RNA [LCSH]
Plant mitochondria [LCSH]