Co-aggregation properties of trimeric autotransporter adhesins
Abstract: Trimeric autotransporter adhesins (TAAs) comprise a group of virulence-related proteins in Gram-negative bacteria. These obligate homotrimeric proteins are embedded in the outer membrane and function as adhesins. Members of this family binds to extracellular matrix components such as collagen and laminin and also confer serum resistance and autoggragation. TAAs have a common N-head-stalk -membrane anchor-C architecture. The aim of my master study is to characterize the co-aggregation properties of TAAs. As model systems, we use two subtypes of TAAs: YadA from the enteropathogens Yersinia enterocolitica (YeYadA) and Y. pseudotuberculosis (YpYadA), and the immunoglobulin-binding Eib proteins from Escherichia coli, EibA, EibC and EibD. Both YadA and the Eibs mediate autoaggregation. The autoaggregation mediated by these proteins is homotypic (i.e. YadA binding to YadA, EibD binding to EibD etc.), but it is not known whether TAAs can mediate heterotypic interactions (e.g. YadA binding to EibD, i.e. co-aggregation between different TAAs). In order to answer this question, we co-expressed a fluorescent label (GFP or mCherry) together with a particular TAA and followed the interaction using fluorescent readout. Results show that there is co-aggregation between some population expressing different TAAs, which can be explained by relatively high sequence similarity between the interacting TAAs. In most cases, the level of co-aggregation correlated with the sequence similarity. However, in other cases the TAAs did not interact, showing exclusion of non-self-bacteria.
A multi-gene phylogeny of the green algae (Chlorophyta)
Abstract: The advent of high-troughput transcriptome sequencing has drastically improved the data available for constructing phylogenies with a denser taxon and gene sampling than what has previously been possible. With copious amounts of data readily available for analysis, I combine results from several previous studies in order to investigate the relationships between the ecologically and morphologically diverse groups of green algae (Chlorophyta).The resultant phylogeny will serve as a background to generate hypotheses about the cytomorphological evolution and codon evolution among the core Chlorophyta.
Evolution and molecular function of IDA-LIKE peptides
Abstract: Inflorescence deficient in abscission (IDA) is a small peptide ligand which binds to the leucine-rich receptor-like kinase HAESA (HAE) and HAESA-Like 2 (HSL2), and has been shown to be regulating cell separation events both in reproductive organs and in the root tip of the model plant Arabidopsis thaliana. IDA belongs to a small family of IDA-LIKE proteins with a common 12 amino acids long motif, which for IDA and IDL1 have been shown to be binding and activating these receptors. A recent phylogenetic analysis indicated that IDA and HSL2 were present in the common ancestor of the flowering plants. All flowering plants investigated up to now have, besides orthologues of IDA, several IDL genes. Genetic and biochemical evidence suggest that IDL1 is functionally very similar to IDA, but nothing is known about the function of the other IDL genes. I will sort out the phylogenetic relationship of the IDL genes and identify the processes in which they are involved by studying recently generated single, double and triple mutant lines. By comparison of expression patterns and mutant phenotype for IDL- and HSL- genes we hope to identify the receptors specific for the different IDL peptides.