Sterol Biosynthesis Contributes to Brefeldin-A-Induced Endoplasmic Reticulum Stress Resistance in Chlamydomonas reinhardtii

Putative Endoplasmic Reticulum Stress Inducers Enhance Triacylglycerol Accumulation in Chlorella sorokiniana

Chlorella, recognized for its high lipid and protein content, is increasingly studied for its potential in the food and bio industries. To enhance its production and understand the underlying mechanisms of lipid accumulation, this study investigated the role of endoplasmic reticulum (ER) stress in modulating lipid metabolism in Chlorella sorokiniana UTEX 2714, using six putative ER stress inducers: 2-deoxy-D-glucose (2-DG), dithiothreitol (DTT), tunicamycin (TM), thapsigargin (TG), brefeldin A (BFA), and monensin (Mon). The results showed that 2-DG, DTT, TM, BFA, and Mon significantly inhibited cell growth in C. sorokiniana. Treatment with 2-DG, DTT, TM, BFA, or Mon resulted in substantial increases in the triacylglycerol (TAG) to total fatty acid (tFA) ratio, with fold changes of 14.8, 7.9, 6.2, 10.1, and 8.9, respectively. Among the tFAs, cells treated with these compounds exhibited higher levels of saturated fatty acids and lower levels of polyunsaturated fatty acids (PUFAs). In contrast, the fatty acid composition of TAGs showed the opposite trend, with relative enrichment in PUFAs. This study enhances our understanding of Chlorella lipid metabolism, providing valuable insights for optimizing lipid production, particularly TAGs enriched with PUFA content, for applications in functional foods, nutraceuticals, and sustainable bioresources.

Stress on the Endoplasmic Reticulum Impairs the Photosynthetic Efficiency of Chlamydomonas

Stress on the Endoplasmic reticulum (ER) can severely disrupt cellular function by impairing protein folding and post-translational modifications, thereby leading to the accumulation of poor-quality proteins. However, research on its impact on photosynthesis remains limited. In this study, we investigated the impact of ER stress on the photosynthetic efficiency of Chlamydomonas reinhardtii using pharmacological inducers, tunicamycin (TM) and brefeldin A (BFA), which specifically target the ER. Our measurements of photosynthetic parameters showed that these ER stress-inducing compounds caused a significant decline in photosynthetic efficiency. A proteomic analysis confirmed that TM and BFA effectively induce ER stress, as evidenced by the upregulation of ER stress-related proteins. Furthermore, we observed a widespread downregulation of photosynthesis-related proteins, which is consistent with the results obtained from our measurements of photosynthetic parameters. These findings suggest that the stress on ER has a profound impact on chloroplast function, disrupting photosynthetic processes. This study highlights the critical interdependence between the ER and chloroplasts, and it underscores the broader implications of ER stress on the cellular metabolism and energy efficiency of photosynthetic organisms.