3 Postdoc Positions in Plant Physiology and Medical Biochemistry and Biophysics (2016)

Project description: Mediator is an evolutionarily conserved multiprotein co-regulator complex and a central player in the stress response and acclimation processes. It integrates external cues perceived by different receptors, by transferring signals from promoter-bound transcription regulators to RNA polymerase II (Pol II).

Mediator orchestrates major changes in chromatin structure and nuclear gene expression, which are essential for balancing cellular energy metabolism and mediating plant and fungal stress responses. However, several aspects of Mediator function are still elusive, especially questions about how specific Mediator subunits integrate signals from different pathways and how they transfer these signals to Pol II in order to regulate expression of the specific target genes that are required for a coordinated cellular response.

Our main hypothesis is that different stress responses converge on specific subunits of the Mediator co-activator complex in an evolutionarily conserved manner and this will be tested using a comparative evolutionary approach using four different model organisms; two distantly related fungi: the yeast Saccharomyces cerevisiae and the filamentous fungus Neurospora crassa, and two distantly related plants: the angiosperm Arabidopsis thaliana and the moss Physcomitrella patens.

Postdoctoral project 1: Identify target genes and the role of Mediator in biotic and abiotic stress responses in plants

In collaboration with other groups in the project, the candidate will use RNA seq to study transcriptional changes in Arabidopsis under diverse types of stress. The focus will be to find co-regulated genes within and between plants and fungi in order to identify stress-regulated genes. The next task will be to identify genes that are dependent on specific Mediator subunits for expression under stress. The focus will be on non-essential Mediator subunits which can be studied by knockout mutations. Candidate genes that are regulated by a specific Mediator subunit will be examined for common regulatory motifs in order to identify transcription factors that bind to these motifs. The role of these transcription factors in specific stress responses will be studied by analysing the transcriptional and physiological response of mutants in their target genes under stress conditions. Contact: Professor Stefan Björklund,stefan.bjorklund@umu.se

Postdoctoral project 2: Identify the sources of the stress signals that are received by Mediator.

The candidate will study how the Mediator function as a regulatory hub integrating stress signals originating in different cellular locations to control changes in gene expression required for the acclimation to stress. To address this question you will use combinations of mutations in Mediator subunits, mutations in retrograde signaling pathways and mutations in cytosolic signaling components in yeast and Arabidopsis.

In addition, the response of Mediator will be analyzed following exposure to inhibitors of energy metabolism, respiration and photosynthesis. Thus, using genetic analysis in combination with biochemistry and physiology the candidate will reveal how the signals originating in different cellular locations are integrated, and if certain signals are dominant to others in generating the final changes in gene expression. Contact: Professor Åsa Strand, asa.strand@umu.se

Postdoctoral project 3: Investigate cellular localization of and interactions between proteins involved in the Mediator controlled response to stress.

The candidate will primarily use green Arabidopsis cell cultures developed at Umeå Plant Science Centre. Stable transgenic lines will be generated in this cell line and a range of Fluorescent Fusion Proteins of signaling components, Mediator subunits and specific transcription factors will be produced. The generated Arabidopsis cell lines will be used to in vivo investigate localization during different conditions causing changes in cellular energy status and/or stress of key components and interactions between the proteins involved in the Mediator controlled response to stress. Contact: Professor Åsa Strand, asa.strand@umu.se

Qualifications / Requirements: Successful candidates will have a PhD degree, or equivalent, in molecular biology or biochemistry. Experience with plants as experimental systems is an advantage. To be eligible for this fellowship, you should have completed your doctoral degree maximum three (3) years before the end of the application period. The candidate should have extensive laboratory experience with biochemical methods, specific knowledge about confocal microscopy is an advantage. Also the candidate should be comfortable being part of a team as well as doing independent research. Good skills in the English language are essential.