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Structure, function and regulation of plant Translocator (TSPO) proteins

A major challenge in plant research is to secure and increase crop yields under sustainable conditions without exploiting potentially limiting resources. This would require an in-depth understanding on the complement of changes plants undertake under unfavorable growth conditions (stressful conditions) to cope with such transient of permanent conditions. Environmental conditions such as high salt, reduced water in the soil, high or low temperature, collectively known as abiotic stresses, are detrimental to plant growth and development worldwide. In presence of such insult, plants induce the expression of a set of selective genes to mount a response to cope with the damage induced by these environmental cues.

The ongoing research in my laboratory aims at understanding the biological role and regulation of an abiotic stress-induced membrane protein in plants, TSPO (Translocator protein-related), with the main focus on AtTSPO from the model plant Arabidopsis thaliana. TSPO proteins are known to be a common response to stressful conditions in bacteria or mammalian cells although their biological is still not well understood. For example, a human TSPO protein is up-regulated in some cancer cells and or inflammation, and is used as a diagnosis imaging marker for some brain ailments such as neurodegenerative diseases. 

Because plant proteins such as AtTSPO are only expressed during stressful conditions, their biological role is only required transiently. Thus, the plant cell should have and efficient molecular mechanism to control their expression when required, and their degradation when their function in no more necessary. Understanding when and how stress-induced proteins are degraded have been mainly overlooked in plants. Studying AtTSPO so far has uncovered an intriguing connection between lipids and porphyrins metabolism, stress signaling, and autophagy as a selective pathway for the degradation of this stress-induced protein. We found that AtTSPO acts as a scavenger of excess free porphyrin produced during stress, and regulates water use by the cell through specific protein-protein interactions.

These various aspects of plant TSPO biology are studied to understand the underlying molecular mechanisms, and possibly, how tempering with these mechanisms, at least in part, could be beneficial to crop and non-crop subjected to abiotic stresses.