Sphingolipids are ubiquitous and essential components of eukaryotic cells. Analytical profiling of their content in different biological systems is limited by difficulties in extracting them, and detection and quantification is limited by their large, amphipathic, and complex structures. Studies of the precise functions of sphingolipids in vivo is also challenging, here due to lethality of mutants generated for study using standard knock-out mutagenesis, and well as pleiotropic phenotypes of non-lethal mutants, or RNAi lines.
The metabolism and functions of sphingolipids is fundamental knowledge that we need for understanding and interpreting broader biological processes. This includes further basic, foundational research as well as applied investigation into, for example, programmed cell death in plants that is associated with accumulation of simple sphingolipids (ceramides and long chain bases (LCBs)), or human metabolic disorders caused specifically by defects in sphingolipid metabolism (e.g. Tay-Sachs disease, Gaucher disease, and Niemann-Pick disease).
With this action, I set out to (1) better understand sphingolipid metabolism in plants by developing optimized analytical approaches. I joined the Department of Plant Biochemistry led by Prof. Ivo Feussner in Göttingen, as they have a state-of-the-art analytical platform and specialized knowledge and decades of experience working with plant lipids. We sought to specifically develop better methods for analyzing glycosyl inositol phosphorylceramides (GIPCs) the most challenging class of sphingolipids to analyze, but also those which are most abundant in plant tissues. A second objective was to better understand the functions of sphingolipids. Here, I anticipated that using a model system with the simplest and most easily-manipulated developmental patterning and organ structure would facilitate interpretation of complex phenotypes. To that end, I used the model moss Physcomitrium patens (formerly Physcomitrella patens). I set out to optimize CRISPR/Cas9 tools to obtain collections of higher-order mutants in gene families required for GIPC biosynthesis, and also optimize our approach to specifically obtain knock-down genotypes where knock-outs would be lethal. Finally, I set up a forward-genetic screen in P. patens, selecting mutants that were resistant to programmed cell death caused by LCB accumulation after treatment with a fungal inhibitor of sphingolipid biosynthesis. This screen was designed to improve our understanding of the link between sphingolipid content and programmed cell death in plants.
The concrete research output of this action includes improved methods for analysis of sphingolipids, improved methods for genetic manipulation of P. patens and its further development as a model system, and mutant phenotypes that pinpoint functions of GIPCs in plants. These serve the broader research community and have also locally served to establish a highly-productive, specialized work cluster in my host lab in Göttingen. The specialized skill set I have obtained through training with the analytical platform unique to my host lab will support my next career step and help me obtain an independent position.
