Meeting Abstract
Our understanding of protein liquid-liquid phase separation (LLPS; ‘membraneless organelles’) and its importance in a wide range of biological phenomena is rapidly growing. Unexpectedly, protein LLPS may also play a role in the desiccation- and osmotic-stress tolerance of encysted Artemia franciscana (brine shrimp) embryos. AfrLEA6 is an intrinsically disordered protein in Artemia that shares homology with seed maturation proteins (SMPs) found in some plant seeds. SMPs have been linked to the duration in which a seed remains viable in the dried state. Therefore, it was hypothesized that AfrLEA6 may play a role in sustained tolerance to water stress. This hypothesis was tested by ectopically expressing AfrLEA6 in desiccation-sensitive Drosophila melanogaster (Kc167) cells and exposing these cells to water stress. AfrLEA6 was found to increase both desiccation and osmotic-stress tolerance of Kc167 cells. Furthermore, confocal microscopy was used to image LLPS of AfrLEA6 in vivo. Staining cells with Nile Red, a lipophilic dye, suggested that AfrLEA6 causes the cytosol to interact with Nile Red like an aqueous-organic cosolvent mixture. Altered solvent properties may decrease the thermodynamic stability of unfolded proteins and reduce native protein conformational mobility yielding cytosolic wide stabilization of native proteins. Altogether, these data support the hypothesis that AfrLEA6 plays a role during water loss and indicates that AfrLEA6 significantly impacts the physicochemical properties of the cytosol. (Supported by NSF IOS-1659970.)
