Features of heat-induced aggregation of chloroplast proteins in Chlamydomonas reinhardtii

Abstract

In my research group, we aim to understand biogenesis and homeostasis of chloroplast proteins. The topics include synthesis and folding of chloroplast-encoded proteins and the challenges of maintaining homeostasis during temperature stress.

Cells have a relatively small temperature range for optimal growth. The sudden rise of environmental temperatures leading to heat shock occurs frequently and especially affects organisms with limited possibility of stress avoidance such as plants or microorganisms. Heat leads to increased protein unfolding, misfolding, and aggregation, disrupting cellular performance. It is fairly well understood how cells increase the expression of molecular chaperones and proteases to maintain proteostasis by counteracting protein misfolding and aggregation. However, we do not fully understand, which proteins are subject to heat-induced aggregation and if there are common physico-chemical protein features that favour heat-sensitivity. Particularly for chloroplast proteins, we also lack information how proteins aggregate and how such accumulate are cleared during stress relief. In the presentation, I will discuss our unpublished data how we addressed these open questions. We systematically studied the phenomenon of heat-induced protein aggregation in Chlamydomonas reinhardtii cells and performed proteomic studies to reveal the nature of these aggregates. For better understanding the process of aggregation in chloroplasts, we performed cryo-electron tomography and were able to observe plastidic deposition sites and prossible clearance strategies. We hope that our findings will set a fundation for future engineering of more stress tolerant pathways in plant cells.