Communications Between the Endoplasmic Reticulum and Other Organelles During Abiotic Stress Response in Plants

Abstract

To adapt to constantly changing environmental conditions, plants have evolved sophisticated tolerance mechanisms to integrate various stress signals and to coordinate plant growth and development. It is well known that inter-organellar communications play important roles in maintaining cellular homeostasis in response to environmental stresses. The endoplasmic reticulum (ER), extending throughout the cytoplasm of eukaryotic cells, is a central organelle involved in lipid metabolism, Ca²⁺ homeostasis, and synthesis and folding of secretory and transmembrane proteins crucial to perceive and transduce environmental signals. The ER communicates with the nucleus via the highly conserved unfolded protein response pathway to mitigate ER stress. Importantly, recent studies have revealed that the dynamic ER network physically interacts with other intracellular organelles and endomembrane compartments, such as the Golgi complex, mitochondria, chloroplast, peroxisome, vacuole, and the plasma membrane, through multiple membrane contact sites between closely apposed organelles. In this review, we will discuss the signaling and metabolite exchanges between the ER and other organelles during abiotic stress responses in plants as well as the ER-organelle membrane contact sites and their associated tethering complexes.

Keywords: calcium homeostasis; endoplasmic reticulum; lipid exchange and transport; membrane contact sites; reactive oxygen species; unfolded protein response.

Figure 1

Interactions of the ER network with other organelles in plant cells. The dynamic ER network physically interacts with other subcellular compartments, such as the Golgi (cis- and trans-), mitochondria (Mit), chloroplasts (Chl), peroxisomes (PEX), vacuole (Vac), nucleus (Nuc), and the plasma membrane (PM) through MCSs. The pointed extensions of a peroxisome and a chloroplast represent peroxule and stromules, respectively. Question marks indicate MCSs that have not yet characterized. MCS-enriched proteins are directly involved in physical tethering; mediate organelle biogenesis; and regulate exchanges of lipids, Ca²⁺, ROS, and other important metabolites and signaling molecules.