**Abstract**

Stress compromises protein trafficking in plants, which often results in modifications to the endomembrane system and trafficking pathways. Proteins travel in unexpected ways during stress, and cell compartments alter their appearance, activity, and content to cope with the difficulties that stress brings. We will piece together material on the issue in this chapter, emphasizing how the endomembrane system processes such changes and how it reacts to a dynamic environment. The intricate dynamics of protein transport pathways and how they maintain cellular homeostasis under challenging circumstances is illustrated.

**Keywords:** abiotic stress, endomembranes, protein trafficking, vacuolar routes, endoplasmic reticulum

### **1. Introduction**

Diverse environmental stresses frequently trigger signals and pathways that lead to cellular responses, such as increased antioxidant expression, solute accumulation, altered protein transport, and endomembrane remodeling [1–4]. In fact, nowadays, crop failures caused by climate change and human action pose the biggest hazard to human and environmental health through food safety declining [5]. Trying to face this everchanging environment, plants have developed the capacity to adapt to and benefit from changes in their surroundings, activating stress defense mechanisms [6]. The processes behind the stress response are only partially understood, and alterations in the transcriptome are still the outcome of a complex chain of circumstances. One of the most important mechanisms, especially concerning interorganellar connections, occurs at the endomembrane level [7, 8], from which new markers for the assisted selection of stress-resistant crop types can be found. Since the plants' successful adaptation likely relies on balanced interactions and synergistic effects among ordinarily unrelated proteins, defining each participant's precise roles in the game is a crucial aspect of plant genetic improvement [9]. Recent experimental evidence [10] points to a variety of protein classes (including aquaporins, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), ATPase pumps, or channels) that regulate particular membrane transport events, resulting in significant cell reorganization events in challenging environmental conditions. As an example, the AKT1/KC1, a shaker-like potassium channel, was selectively accumulated on small vacuoles [11] and is sufficient to confer stress tolerance when overexpressed. Several research groups discovered intriguing connections between stress tolerance and previously unrecognized membrane rearrangements. However, the relationship between the architecture of membranous structures and their ability to withstand stress has only recently gained the attention of researchers. Numerous research items have supported the notion that endomembrane trafficking is closely related to stress signaling pathways; nevertheless, these studies lack a better understanding of the underlying mechanisms. In the last several years, there has been a notable advancement in our understanding of the mechanisms behind protein sorting. Due to their significance in maintaining the homeostasis of plant cells, particular attention has been paid to the study of proteins that are directed toward the vacuole and the inherent sorting mechanisms. Regarding this matter, recent results imply that alternative routes may challenge the orthodox concept of protein transport to the vacuole [12–14]. These alternative routes are regarded as one of the plant's adaptations to challenging circumstances. As a result, it is believed that certain conditions may cause the vacuolar trafficking pathways to change to better serve the demands of the plant. Alongside the vacuole, the endoplasmic reticulum, as the entrance to the endomembrane trafficking routes, also plays an important role in the folding, quality control, and sorting of newly produced proteins [15–17]. Additionally, as the link between the actin cytoskeleton and the endomembrane system is essential to maintaining many aspects of plant cell function and development, the cell cytoskeleton also plays a significant role in the response and adaptation to stress [18]. This chapter aims at describing the more recent findings on the effects of abiotic stress in the endomembrane system, alterations in vacuolar trafficking routes, and the importance of the cell cytoskeleton in these processes. Also, examples of proteins and endomembrane effectors with altered expression/localization were depicted from the available literature that can represent a collection of putative markers for abiotic stress studies (**Table 1**).
