Areas of Major Research Activities
Research activities are focused on extrachromosomal genetics and biochemistry in higher plants. Mitochondria – the power stations of the cell – influence a variety of different traits, e.g. cytoplasmic male sterility (CMS) and non – chromosomal stripe (NCS). CMS is an agronomically important trait which is widely used in hybrid breeding. At present the main research objects for a molecular genetic and biochemical analysis of CMS are cabbage, rape seed and Vicia faba. Arabidopsis is also being used as a model plant especially for an investigation of its complete mitochondrial protein content.
Characterization of male sterile cytoplasms for hybrid breeding in cabbage (Brassica oleracea)
Temperature dependent instability of the self-incompatibility system of Brassica makes a cytoplasmic male sterility system for hybrid breeding highly desirable. As no reliable CMS system was found in the genus Brassica, cytoplasms from Raphanus were transferred to Brassica by Japanese scientists. The most widely used cytoplasm is the „Ogura“ system which is now covered by several patents. Thus breeders are seeking alternative reliable cytoplasms.
We have carried out a molecular genetic and biochemical analysis of the autoplasmic CMS “Tokumasu“ system and the alloplasmic CMS “tournefortii“. The male sterile plants of the latter system have a mitochondrial DNA which is recombined between Brassica tournefortii and Brassica napus. An open reading frome (orf 263) in the 3’ region of the mitochondrial gene for submit 6 of ATP-synthase codes a polypeptide of 263 amino acids. This orf 263 has been discussed by Landgren et al. (Plant Mol. Biol. 32, 879-890) as a candidate for causing pollen sterility. We found orf 263 not only in the sterile but also in the fertile line and sequenced both. Interestingly orf 263 is not transcribed in fertile or male sterile lines of our CMS “tournefortii“. On the other hand we have found differences in the transcription of other mitochondrial genes between male sterile and fertile lines.
Analysis of mitochondrial mutants
Two-dimensional separation of protein complexes from mutant mitochondria by BN-PAGE is a powerful tool for the investigation of mitochondrial mutants. The method allows to analyse the protein composition from normal and mutant plants. Differences are due to mitochondrial or nuclear genes and are the starting point for the analysis of the cause of the mutations analysed.
Proteomic approach for the analysis of cytoplasmic male sterility in rape seed
Proteome analysis is a powerful tool for the characterization of proteins involved in cytoplasmic male sterility. Our proteomic studies of CMS are based on the resolution of mitochondrial proteins by 2 D-gel electrophoresis and identification of the resolved proteins by mass spectrometry or protein sequencing. A comparative analysis of mitochondrial proteins from male sterile and fertile isogenic lines allows the direct identification of mitochondrial proteins which are quantitatively or qualitatively affected by the male sterile phenotype. Our investigations of the mitochondrial proteins from Brassica napus lines carrying genetic information from Brassica tournefortii in their mitochondria revealed characteristic features of the male sterile system “tournefortii“. An analysis of mitochondrial proteins from different tissues and developmental stages should provide more insights into the proteins affected by the male sterile phenotype.