PhD student in biology

Swedish UKniversity of Agricultural Sciences Department of Forest Genetics and Plant Physiology in Umeå 1 PhD student in the research education subject: Biology Cell wall biosynthesis regulation via the endomembrane system The cell wall of plants provides mechanical strength, defines cell shape and plant morphology, and is a protection from pathogen attack. The cell wall is composed of different polysaccharides including cellulose microfibrills that are embedded in a hemicellulosic and pectic matrix along with proteins. The regulation of cell wall dynamics occurs at multiple levels but is particularly influenced by the endomembrane system and the secretory pathway. The biogenenis and maintenance of the endomembrane compartments, plasma membrane (PM) and cell wall all rely on vesicular trafficking, which involves vesicle formation, transport and fusion with target membranes. Endocytosis is the process of cellular ingestion by which the PM invaginates inward to deliver cargo molecules into the cell or to regulate protein amounts at the PM. This phenomenon is extremely important in fast developmental responses. Chemical biology is the use of small molecules to modify or disrupt the function of specific proteins. The power of this approach is the ability to study protein function in vivo with precise control of rapid endomembrane trafficking processes response via bioactive chemicals. A large-scale screen (50, 000 compounds) of unbiased libraries of diverse small molecules has identified 129 novel bioactive molecules valuable for the characterization of endomembrane trafficking pathways. Identification of compounds that specifically alter the trafficking of proteins involved in the synthesis and the deposition of the primary cell walls Preliminary experiments indicate that among the 129 bioactive compounds, 60 are potential inhibitors of endocytosis. Using FT-IR microspectroscopy (Mouille et al., 2003), the PhD student will evaluate the impact of selected compounds on cell wall composition and structure in Arabidopsis thaliana. This study will allow the classification and selection of compounds according to their effects on cell wall composition. In addition, the PhD student will conduct detailed macro-level phenotypic analyses of Arabidopsis thaliana seedlings resulting from selected compounds. This study will be implemented by a cell biology approach. Using Confocal Laser Scanning Microscopy (CLSM), different transgenic lines expressing subcellular fluorescent markers will define the chemically targeted endomembrane pathways. The compounds that specifically perturb cell wall composition and structure will be used as probes to evaluate the trafficking of KOR1 and CESA3, two proteins intimately involved in cellulose biosynthesis. Identification of new molecular components involved in cell wall biosynthesis and deposition To discover novel genes involved in trafficking and wall composition and structure, selected lead bioactive compounds will be used to selection for compound-specific resistant or hypersensitive mutants. For this purpose, an EMS mutagenized population would be created in an Arabidopsis thaliana line expressing a essential protein for cell wall biosynthesis, such as KOR1 fused with a fluorescent protein. Mutants will be characterized and the most promising will be mapped using a rapid combination of rough mapping (50 - 100 individuals) using confocal microscopy and Illumina next generation sequencing to identify mutations. For a complete advt: http://externt.slu.se/sv/Utbildning/Forskarutbildning/Nya-doktorand