Ribosome biogenesis is one of the major biosynthetic pathways, which, for eukaryotes, is best understood in Saccharomyces cerevisiae. Yeast ribosomes consist of 79 ribosomal proteins and four ribosomal RNAs (rRNAs). The assembly of the ribosomal subunits is a highly complex process that involves more than 200 cofactors. An exponential grown yeast culture builds around 2000 ribosomes per minute per cell, uses 60 % of its energy for this process and ca. 10% of the genome capacity is taken by ribosome biogenesis. This clearly underlines the importance of ribosome biogenesis for a living cell.
We are studying ribosome biogenesis in higher eukaryotes with focus on the model plant Arabidopsis thaliana. The general scheme of ribosome biogenesis is conserved throughout eukaryotes but it also shows differences to the best understood organism, Saccharomyces cerevisiae. Nowadays it is assumed that organism specific cofactors exist because higher eukaryotes have different developmental stages and different tissues. Furthermore it is known that tissue specific ribosomes exist in plants, because several homologs for the ribosomal proteins can be found. For us it is highly interesting to identify these cofactors by the analysis of pre-ribosomal complexes after pulldown experiments or immuno-precipitations and to analyze their special function in ribosome biogenesis. Furthermore, we make use of knock-out (T-DNA insertion) mutants of the potential ribosome biogenesis cofactors to study their influence on growth, development, ribosome biogenesis and rRNA processing. Additionally, these proteins are analyzed biochemically and we have a closer look at their enzymatic activity in vitro.