Preface

The endoplasmic reticulum is a complex and multifunctional organelle present in the cytosol of eukaryotic cells. This organelle is not only essential for calcium homeostasis but also for lipid biosynthesis and protein assembly, folding, and post-translational modification. The endoplasmic reticulum contains domains that control the interaction with other organelles, such as the Golgi apparatus, endosomes, mitochondria, lipid droplets, and peroxisomes. It has been established that energy/nutrient depletion, calcium flux injury, or oxidative stress disrupt endoplasmic reticulum homeostasis and even induce accumulation of misfolded/unfolded proteins leading to endoplasmic reticulum stress. Under conditions of endoplasmic reticulum stress, an adaptive mechanism of coordinated signaling pathways, defined as the unfolded protein response, is activated to return the endoplasmic reticulum to its healthy functioning state.

During aging, there is a noted decrease of the protective adaptive response of the unfolded protein response and an increase of the pro-apoptotic pathway together with endoplasmic reticulum ultrastructural injury. Controlling endoplasmic reticulum stress response, maintaining the appropriate endoplasmic reticulum ultrastructure and homeostasis, and retaining organelles' interplay are crucial aspects of global cellular health.

This book presents a comprehensive overview of the endoplasmic reticulum, including endoplasmic reticulum "ultrastructural anatomy," organelles' interplay, endoplasmic reticulum stress and its implication in plant and human health and disease conditions, and more. The information contained herein can help identify and develop novel therapeutic approaches to endoplasmic reticulum response, which may lead to early detection of correlated stressful and/or disease states.

Dr. Favero Gaia would like to thank all the authors who contributed to the success of this book and the IntechOpen team for their valuable and constant support.

> **Gaia Favero** Anatomy and Physiopathology Division, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy

Section 1
