Stress response of membrane-based cell organelles in budding yeast

Abstract

The organelles of yeast demonstrate diverse morphological traits in response to different stress stimuli. However, there is a lack of systematic reports on the structural changes induced by stress stimuli in all membrane-based organelles. Here, we utilized a set of fluorescent protein-based organelle markers to highlight the distinct characteristics of yeast under various stress triggers, including high temperature, hydrogen peroxide, acetic acid, and ethyl alcohol. We found that all of these organelles undergo alterations in structure or function in response to the four stress triggers we tested. Specifically, filamentous mitochondria rupture into smaller segments when exposed to the above four stress conditions. The structure of the endoplasmic reticulum (ER) remains relatively unchanged, but its function is affected. Additionally, high temperature and hydrogen peroxide can induce the Ire1p-mediated ER unfolded protein response (UPR). The translocation of most nuclear-localized proteins to the cytosol is dependent on the specific stress conditions employed. Under the above stress conditions, the vacuole undergoes fusion, resulting in the formation of a larger vacuole from multiple smaller ones. Meanwhile, acetic acid-induced stress leads to the translocation of vacuole-localized proteins Prc1p and Pep4p to unknown puncta, while Ybh3p relocates from the inner vacuole to the vacuole membrane. Proteins localized in the early Golgi, late Golgi, and late endosomes exhibit distinct traits, such as fading away or mis-localization. The structure and function of peroxisomes, lipid droplets, and autophagosomes also undergo modifications. Furthermore, upon exposure to high temperature and ethanol, apoptosis-related proteins Yca1, Aif1, and Mmi1 aggregate instead of remaining dispersed.