Highlights in plant stress responses: role of the Salt Tolerance-Related Protein in Arabidopsis thaliana and innovative strategies to improve stress resistance in Solanum lycopersicum

Plants have developed adaptations to live and reproduce outside water during the colonization of the emerged lands (Flowers and Colmer, 2015). The various conditions imposed by the terrestrial environment have allowed plants to develop a series of elegant mechanisms to modulate their development and, in some cases, to counteract adverse environmental conditions (Flowers and Colmer, 2015). In today’s fast-changing climate scenario, with higher anthropogenic pressure, the environment is changing rapidly, which exposes crops to strong and sudden pressures and stresses (Guermazi et al., 2019). These conditions threaten global crop production, which is expected to decrease by more than 20% by 2050 (FAO, 2016, http://www.fao.org/3/x5871e/x5871e04.htm). In this context, a better knowledge of plant stresses and defense mechanisms they have developed during evolution is crucial. The concept of stress has been modified and updated over the years. Today, plant stress is defined as “any unfavorable condition or substance that affects or blocks a plant's metabolism, growth, or development” (Lichtenthaler et al., 1988). Furthermore, Lichtenthaler extended the stress concept by differentiating between eu-stress and dis-stress, defining eu-stress as “an activating, stimulating stress and a positive element for plant development,” while dis-stress as “a severe stress that negatively affects the plant and causes damage” (Lichtenthaler 1996; Lichtenthaler 1998). Depending on the nature of the factor determining the stress condition, plant stressors can lead to abiotic stress, arising from an excess or a deficit in the physical and chemical environment, including soil salinity, high temperature, drought, cold, floods, heavy metals in soil, etc., and biotic stress, imposed by other organisms, referring to insects, herbivores, viruses, fungi, bacteria, or nematodes (Figure 1.1). The consequences induced by stresses can differ depending on their intensity and duration, but also on the plant's genotype and developmental condition. In general, stressor signals are perceived at the cell level. This recognition triggers signal transduction pathways, and the information is communicated throughout the plant. Consequently, regulation of the gene expression allows a whole plant response, adjusting plant growth and development to compensate for stress. Failure of this program can result in plant death (Imran et al., 2021) (Figure 1.2).