Plant Proteome in Response to Abiotic Stress

Abstract

Due to their sessile nature, plants have to confront the stresses and develop potent adaptive tactics to survive and thrive or tolerate their adverse effects. Abiotic stresses, pose a severe threat and multiple morphologies, biochemistry, and physiology procedures to agriculture and the ecosystem. On the other hand, reductions in crop yields brought about by abiotic stress are expected to increase as climate change restricts the worldwide utilization of arable lands and indirectly affects crop productivity. Therefore, understanding how plants perceive stress signals and adapt to unfavorable environmental conditions is crucial for future global food safety and security. In this chapter, we summarize the latest findings of the effects of abiotic stresses on molecular changes in plant organisms, cells, and tissues, focusing on the stress-specific sensing biomolecules and mechanisms at the proteome level.

1. Introduction

Food could be a reason for the third world war as severe land competition areas participate in agriculture and habitation. Moreover, food production depends not only on land provided but also on the institutionalization of sustainable crop production related to food safety and security.

It is predicted that by 2050, the world’s population will grow to nearly 10 billion people, and the main issue will be feeding them sustainably. To meet this demand, it is necessary to produce about 50% more food in less than 40 years. And the parameters affecting food production like climate change, scarcity of natural resources, and food-wasting should be considered carefully.

On the other hand, approaching sustainable food availability in agriculture not only depends on a balance between food production sustainability, food security, and food safety, but also to spread food worldwide justly [1, 2].

Hunger and undernutrition are two main consequences of food insecurity. So, finding the solutions to make long-term sustainable agriculture possible concerning its restricting environmental factors is a severe challenge for future studies. As one of the significant environmental factors, climate change is expected to be the most unfavorable challenge for sustainable crop production with consistent and adverse effects on food security in many countries [3, 4]. Climate change could be explained by higher precipitation variability, increasing droughts, or floods accompanied by temperature fluctuation. Findings illustrated that about 90% of arable lands are prone to one or more of the above stresses [5], which cause up to 70% yield losses in major food crops [6].

Agriculture and climate have mutual interaction by affecting each other both positively and negatively. Although, the agriculture industry impacts climate in two main contributions, including leading to approximately 25% of global anthropogenic emissions [7] and about 70% of global water withdrawals [8]. The most serious challenge to reach sustainable agriculture would be environmental stresses with emphasizing abiotic stresses.

Regarding climate impression on-farm activities, climate change could affect crop productivity through direct and indirect pathways. Changes in temperature, water availability, and greater variation in weather conditions are significant direct impact factors [9]. For example, temperature increases cause faster plant growing, shorter cropping seasons, and lower yields subsequently. Moreover, pathways like variation in pests, pathogens, and pollinators could be named indirect effects of environment change on crop yield [10]. For instance, a meta-analysis of 1090 studies on the yield of principal crops subjected to unfavorable environmental conditions confirmed that yield reduction could remarkably happen in long-term agriculture [3].

Environmental alterations’ direct and indirect effects could be managed by developing adaptation mechanisms like using new plant production methods or breeding new plant genotypes resistant/low sensitive to environmental pressure [11]. Identifying and quantifying the role of abiotic stresses on the future of plant products may be detected by using technologies to study plants deeply and finding tolerant related genes, biomarkers, or metabolites to work. Proteomics is a reliable and accurate technique for investigating plants’ responses to various stresses and detecting mechanisms specific to each genotype, stress, or combination of them.

In this chapter, we want to focus on the effects of climate change on agriculture, specifically on the opposing side therefore, various type of abiotic environmental factors limiting plant production at proteome level will be explained with detail and proteomics technology that helps study plants’ proteome profile under stress conditions.

2. Environmental stressors

The environment could positively and negatively affect populations, organisms, and ecosystems; that negative impact is named stressors with variation in intensities. Exposure is the interaction across each organism with an environmental stressor that is specific to time and location. Exposure is defined as short term and long term with intensity variation. Suppose exposure leads to different types of internal or external changes, named as the response. Various categories of environmental stressors have been recognized, including climatic stress, biological stressors, biological pollution, physical stress, wildfire, chemical pollution, thermal pollution, and radiation stress [12]. Climatic stress is the primary factor affecting crop production worldwide by expressing drought, flood, heat, and cold.

In contrast with human beings, farmers cannot control environmental stresses and have to accept them as nature, so studies have been focused on finding mechanisms in plants to keep them productive in average conditions and under unfavorable situations.

3. Environmental stresses on plants

One of the most critical challenges in plant production is the competition of specifying lands for farms or growing population habitations. So, it is vital to produce more in less area considering climate change and anthropogenic activities consequences [13]. Alteration in natural elements like temperature increasing by 3–5°C in the next 50–100 years is proof of extending drought tress, besides human activities such as increasing consumption of chemical fertilizers, pesticides, and improper usage of groundwater resources resulting in salt stress. Therefore, increasing environmental stresses is inescapable from plant productivity in the future [14]. It should be noticed that stress impact not only depends on environmental conditions but also on plant genotype. Therefore, plant reaction to stress is a specific interaction of genotype × environment that could vary depending on these two parameters [15].

In another way, animals counter to negative pressures by escaping and moving, but for immobile plants, stress is the alarm of the typical environment modifying to uncarvable status. Generally, two types of environmental stress, including biotic stress and abiotic stress, are categorized that biotic stress defines plant condition after subjecting to a biological invader. In contrast, nonliving environmental factors are imposed on plants as abiotic stresses [16]. Biotic and abiotic stresses are essential to be studied in detail as they are the main reasons for plant product loss globally [17]. It needs to be considered that the source of environmental pressure affects the synchronism, diversification, or even the extinction of plants, inevitably related to agriculture development [18].

3.1 Biotic stress on plants

Biotic stress results from competition for nutrition absorbing between plants and various aggressive range of pests and pathogens, including viruses, bacteria, fungi, nematodes, herbivorous insects, arachnids, and weeds [19, 20]. The level of plant tolerance depends on its balance in responding to biotic stress [21]. Plant starts to activate individual and combined mechanisms in different morphological, physiological, biochemical, and molecular levels, and interaction across these functions expresses plant sensing of stress [22, 23, 24].

3.2 Abiotic stress on plants

One of the significant climatic changes in the next 50–100 years is surface temperature increasing by 3–5°C that in combination with an increasing trend of drought, flood, and heatwaves, will be expected to influence crop productivity negatively and food safety [25, 26, 27]. For instance, drought and heat stress substantially affect seed yields by reducing seed size and number, consequently loss in trait ‘100 seed weight’ and seed quality [28].

Environmental abiotic stressors include drought (water stress), excessive watering (waterlogging) and submergence, extreme temperatures [high and low (chilling, cold, freezing)], salinity due to excessive Na⁺, deficient or over essential nutrients, chemical factors (heavy metals and pH), extreme levels of light (high and low), radiation (UV-B and UV-A), gaseous pollutants (ozone, sulfur dioxide), mechanical factors, and other less frequently occurring stressors trigger plants negatively by crop quantity and quality losing [5, 20, 29, 30, 31, 32, 33, 34]. Importantly, abiotic stresses cause dramatic detriment in various species and some to 50% yield limitation [32, 33]. It should be noted that about 90% of farmlands are exposed to at least one of the above abiotic stresses [5].

3.2.1 Drought stress

Agriculture is accounting for 70% of total freshwater worldwide usage on average. Therefore, human water consumption competes with agriculture water demand, so it impresses the water availability for commercial plant production with the effect of drought stress [34]. The universal water deficiency directly limits plant production while earth temperature increasing with the trend of warming around 0.8°C over the past 100 years has an indirect effect. For example, global barley production reduces by 10% with each 1°C temperature increase [35, 36]. One of the approaches to accompany plants with growing drought stress could be water use efficiency (WUE). For instance, drought stress remarkably impacts nearly 23 million hectares of rain-fed rice-growing area in Southeast Asia [37]. By developing WUE, plants will use water more efficiently, suitable for drought stress tolerance [38]. Some of the primary effects of drought stress on plants are reducing plant growth rate, photosynthetic function, CO₂ concentration, and molecular metabolism [38].

3.2.2 Salt stress

Soil salinity is not only caused by environmental activities or factors like environmental pollution, especially in arid and semiarid arable lands but also could be related to drought stress by a deficiency in water resources. Salinity directly limits crop productivity, food safety, and agriculture sustainability by gradually cultivating salinized lands [39, 40]. The severity of salinization could be sensed better by finding that around 970 million hectares, 8% of arable lands, are impacted by a high level of salinity stress [41].

Specific effects of salt stress on plants could be explained physiologically by reducing seedling germination percentage, shoot and root length, fresh and dry weight, and necrotic leaf tissue morphologically and K⁺ and Ca²⁺ level deficiency continued with osmotic and oxidative stresses at the molecular level, especially in plant leaves [42, 43, 44, 45].

3.2.3 Temperature stress

Temperature stress is a geographical dependent variable that defines high-temperature stress and low-temperature stress. Suppose the climate condition declines to less than 15°C, known as chilling or cold stress, while by greater decreasing to less than <0°C, freezing stress happens. Generally speaking, low-temperature stress is detrimental stress detracting plant growth and yield by affecting germination, seedlings growing, the color of leaves, and tillering continued in declining pollen sterility [46, 47].

Against low temperature, increasing temperature to a higher level than plants tolerance modifies plant growth and productivity negatively. High temperature or heat stress disturbs a plant’s average growth morphologically, physiologically, and in molecular aspects like protein degradation or modification, instability of enzymes, nucleic acids, biomembranes, and cytoskeletal structures [48].

3.2.3.1 Cold stress

Cold and freezing stresses affect plant production significantly by decreasing production or even plant death. The plant generally adapts to such severe stress conditions to survive; however, many plants cannot tolerate it [14]. Cold stress categorizes plants, with different resistance levels, into three groups: delicate chili plants that are highly sensitive to a low temperature just lower than 15°C and damage seriously. The second category, chilling resistant plants, which are medium tolerant to cold stress and are temperature around 0°C, causes stress. Nevertheless, the last plant group is frost-resistant plants that acclimate to shallow temperatures even by ice formation. Cold stress resulted in membrane instability, ion exchange disturbance, and electrolyte leakage [49].

3.2.3.2 Heat stress

Temperature increasing is a severe concern of future plant productivity. Heat stress impacts plant productivity variously in morphological, biochemical, and molecular levels. Plant growth and development decrease, seed germination decline beside photosynthetic lower efficiency all together trigger yield loss as a consequence of heat stress [14, 50]. Another effect of high temperature is accelerating plant growth, especially during the vegetative stage, to mature faster by fruit or seed production. Notably, heat stress could signal drought stress by increasing transpiration and, finally, water evaporation [51].

3.2.4 Heavy metal/metalloids

Soil plays a vital role in plant growth by providing nutrients; however, the amount of soil solution determines whether to call them nutrition. Heavy metal toxicity results from the high concentration of metalloids contaminate the soil with the possibility of absorbance into plant tissues and frustrating plant normal life cycle [52]. Unlikely, metal toxicity is predicted to cause mutagenic impacts on crops due to improper and sewage wastewater irrigation methods, redundant adding of chemical fertilizers to the soil, and rapid industrialization [14, 53]. Two main metal categories are recognized in soil that may lead to mental stress, namely vital micronutrients for average plant growth that become toxic if accumulating in excess in soil solution (Fe, Mg, Mo, Zn, Mn, Cu, and Ni) and non-essential elements with unknown physiological and biological function; however can damage the plant by accumulating in the soil even in modicum amounts (Ag, Cr, Cd, Co, As, Sb, Pb, Se, and Hg) [54, 55, 56]. These vital elements are crucial for enzyme and protein structure in plants, but their excessive presence is not helpful and causes abiotic stress in plants [57].

3.3 Effect of abiotic stress on plants

Plant adaptation in response to abiotic stresses includes a matrix and interaction of various morphological, biochemical, and molecular mechanisms. Morphological alterations are the visible symptoms, representing plant unfavorable condition after stress subjection. However, the number of unique responses happen in the plant adaptation process, some of the common effects like wilting due to water flow decrement, reduction in photosynthetic ability with the result of tiller number decreasing, reducing leaf growth, and increasing root length [58, 59].

Many biochemical mechanisms inducing adaption to stress in plants are regulated by increasing phytohormones levels [60]. Abscisic acid (ABA), jasmonic acid (JA), and ethylene are the main hormones leading to secondary stresses in plants such as osmotic and oxidative stresses [33, 61, 62]. Oxidative stress results from reactive oxygen species production, which generally happens in response to extreme temperature treatment. In contrast, salt and drought stresses lead to an osmotic imbalance in cells and cause osmotic stress [63]. By concomitant osmotic and oxidative stress under abiotic stresses, plant changes biochemically with some common responses like stomatal closure, reducing photosynthesis-related variables like gas exchange factors, declining photosynthesis, and increasing reactive oxygen scavenging activity [59]. Notably, the photosynthesis mechanism is a crucial physiologic parameter influence on yield output, and increasing in related variables helps plant adaptation experiencing unfavorable conditions [64, 65]. Positive induction of phytohormones in stress-subjected plants signals overexpression of the genes related to stress tolerance [66].

A comprehensive understanding of stress responses in plants needs to study the whole network interaction happening in plants involving individual or shared responses. Molecular mechanisms including proteome, transcriptome, genome, and metabolome modification analysis help find genes responsible for plant tolerance under abiotic stress [67, 68]. Genes encoding proteases, chaperonins, enzymes of sugar, proline, ion, and water channel proteins, enzymes contribute to oxidative stress, transcription factors (TFs), and protein kinases help to protect the plant against abiotic stress by overexpression [69]. Moreover, phytohormone signaling regulates some genes like ABA-dependent factor expression after exposure to abiotic stress. Basic leucine zipper (bZIP) TFs are an example of this category, leading tolerance-related responses like stomatal closure and expression of dehydration tolerance genes. However, there is another category of ABA-independent mechanisms [70].

3.4 Plant proteome profile alteration under abiotic stress

3.4.1 Proteomics technology

As the proteome is dynamic in plants both in control and stress conditions, its profile analysis is not only an appropriate approach to study related genome function but also is informative to analyze post-translational modification, protein-protein interactions, protein regulation mechanisms, and metabolic networks [71, 72, 73]. Therefore, proteomics is a powerful tool to identify genes responsible for stress tolerance. Moreover, proteome identification and physiology analysis could provide information to detect genome, stress, or term-related genes or potential biomarkers for a better description level of stress tolerance in each genotype [74].

Mass spectrometry assists with chromatographic instrumentation, and electrophoretic techniques are the primary method for proteome identification and quantification [75]. The application of advanced proteomics technologies like isobaric tags labeling allows characterizing a more significant number of proteins with lower abundance [76].

3.4.2 Proteome alteration under abiotic stress

Plant response to stress in four phases depends on the severity, duration, or recovery process, including the alarm, acclimation, resistance, and exhaustion phases. In the aspect of proteome level, the alarm phase involves modification in signaling-related proteins [77, 78]. Tolerant genotypes shift to the acclimation phase by activating energy and protein metabolism due to the high demand of energy production for enzymes activity. Glycolysis is one of the carbohydrate catabolism that upregulated under the acclimation process in contrast with enzymes related to the biosynthesis of energy-rich compounds like sucrose synthase [77, 79]. Protein metabolism defines a balance between protein biosynthesis and degradation to keep protein homeostasis in plants. The acclimation phase considers as one of the significant differences in proteome changes across stress-tolerant and stress-sensitive genotypes.

There are two main categories of proteins that participate in plant response to stress; the first group contains functional proteins. Late embryogenesis abundant (LEA) protein family plays a crucial role in tolerance mechanism in plants and found increasing in abundant under drought, heat, salinity, cold, and mechanical wounding [80, 81, 82, 83, 84]. Dehydrins are one group of LEA proteins whose overexpression under abiotic stress acclimate plants to abiotic stress, though their exact function is still unclear [85]. Another group of functional proteins is the heat shock protein (HSP) family and chaperones. These proteins are responsible for protecting proteins from aggregation and misfolding and consequently avoiding imbalances in cellular homeostasis. Many reports show that HSPs and chaperons are crucial in plant tolerance after exposure to abiotic stresses like extreme temperatures and drought stresses [86].

Enzymes cooperate in plant tolerance by two mechanisms, including energy production, as discussed before, and ascorbate peroxidase (APX) and catalase are two examples of proteins correlated to detoxification of reactive oxygen species (ROS) in response to abiotic stress like low-temperature conditions [87]. For example, accumulation of H₂O₂ as signal transduction molecule in response to abiotic stress, triggers to cellular damage, and inhibition of photosynthesis [88].

In response to different abiotic stress in plants, stress-induced signal transduction pathways initiate by various signaling receptors includes reactive oxygen species (ROS) [89, 90, 91]. Most dominating ROS include hydrogen peroxide (H₂O₂), hydroxyl radical (OH*), singlet oxygen (1O₂), superoxide radical (O₂*₋), etc. [92] that induced ROS overproduction serves various signaling cascades to regulate stress responses in plants like acclimation or defense by activating downstream metabolic pathways [90, 91, 93, 94]. Studies have found that ROS plays pivotal role mainly as primary signals under unfavorable conditions and interact with other signaling molecules like calcium, MAPKs, plant hormones, and transcription factors [95]. Oxidative stress is the consequence of any misbalance between ROS production and scavenging in plants, lead to proteins function and structure altering and damaging DNA, RNA, and other molecules [96, 97, 98].

In addition to ROS, phytohormones are activated under unfavorable condition by modulating stress-adaptive signaling cascades. Abscisic acid (ABA) regulates various physiological processes ranging from stomatal opening to protein storage and coordinate complex stress-adaptive signaling cascades. ABA is also an important messenger that acts as a critical regulator in activating plant cellular adaptation to different environmental stress conditions [99, 100].

The other functional proteins related to stress tolerance involve ion transporter and membrane proteins that help keep membrane stability by an incredible increase. V-ATPase and channel proteins (NHX-1) increased under salinity in plants [85, 101].

The second group of proteins activated under stress is regulatory proteins, namely, photosynthesis-related proteins, Transcription factors (TF), kinases, phosphatases, and signaling proteins [85]. The photosynthesis mechanism has a very crucial role in plant reaction to stress. Plant decreases photosynthesis-related proteins abundant as try to slow down the growth pace to avoid death happening and closing stomata to avoid water loss, such as RubisCO and chlorophyll a-b binding proteins in both photosystems (PS) I and II found downregulated under low temperature and flood stress [102]. Transcription factors (TF) generally regulate genes expression under stress with the ability of binding specific sequences to these genes and lead tolerance in plants exposed to stress [103]. Mitogen-activated protein kinase (MAPK) is an example of kinases proteins with a particular function in regulating plant responses to unfavorable environmental conditions [104, 105]. On the other hand, kinases coordinate in stress tolerance by the phosphorylation mechanism. Several kinases are found with this function, such as CDPK, MAPK, and SnRK2 [106]. The major subcellular organelles, whose functions get affected under abiotic stress, are the nucleus, mitochondria, chloroplasts, peroxisomes, plasma membrane, and cell wall. Most of these organelles have the potential to become a source of ROS.

3.4.2.1 Proteome response to salt stress

Salinity stress represents enhanced levels of salt ions in soil water solution. As a consequence of enhanced ion levels, decreased soil water potential reveals a so-called osmotic effect on plant cells [78].

Increasing salt (mainly Na⁺) accumulation which is known as salt stress in plants, leads to several metabolite modifications; however, the plant species, the age of the plant, and Na⁺ concentration are three main factors affecting the stress severity. For example, by increasing Na⁺ concentration, salt stress ranges from osmotic stress to osmotic shock [107]. In the short term, high Na⁺ and Cl⁻ concentration causes osmotic stress by misbalance in intracellular ion homeostasis due to decreasing K⁺ transport with excess toxic intracellular Na⁺ ions in the cytosol; therefore, plants exposes to ionic stress [108, 109].

Osmotic stress affects plant cellular metabolism in different ways like membrane fluidity, production, and accumulation of reactive oxygen species (ROS) and further oxidative stress happening, photosynthesis malfunction by stomatal conductance decreasing [108, 109, 110]. The K⁺/Na⁺ discrimination ratio causes inhibiting K⁺ ion uptaking as a vital factor related to many growing and development functions in plants indirectly leads to plant death [111]. To balance ionic homeostasis, an increase in the concentration of cytosolic Ca²⁺ activates some proteins like antiporters and enzymes involved in the transport of ions and phospholipases [112]. Induced accumulation of Ca²⁺ activates H⁺-ATPases as an ion-transporting protein to maintain cytosolic ion homeostasis. On the other hand, the elevated activity of H⁺-ATPases is vital to avoid electrochemical gradient misbalance and maintain cellular pH homeostasis [113, 114].

Osmotic stress is another consequence of a high concentration of Na⁺ in soil, which could be considered a primary signal of ionic stress. Plants sense the osmotic stress by losing leaf water due to high salinity and water capacity absorption decreasing. Therefore, salinity is known as hyperosmotic stress [108, 115]. Na⁺ uptaking to plant roots happens via apoplastic or symplastic routes through Na⁺ transport transmembrane proteins and Na⁺/H⁺ exchangers.

Oxidative homeostasis is misbalanced due to photosynthetic activity and energy metabolism reduction, which induce the accumulation of ROS. Intracellular ROS is a critical signaling molecule promoting oxidative stress induction [41, 116]. Excess ROS accumulation, recognized as a marker of oxidative stress, may be removed by ROS scavengers. Two main groups have been found responsible for oxidative stress response in plants like enzymatic or non-enzymatic antioxidants. Antioxidant enzymes are identified by ameliorating some antioxidative enzyme activities, while other antioxidant mechanisms could play more effective participation in oxidative response [117, 118]. Recent studies on crop plants have identified the following five main groups of proteins that present differential abundance and are directly related to salt stress response mechanisms: (I) heat shock proteins (HSPs), (II) late embryogenesis abundant proteins (LEA proteins), (III) osmolyte and flavonoids biosynthetic enzymes, (IV) proteins involved in carbon, photosynthesis and energy metabolism like rubisco activase, kinases, and oxygen-evolving enhancer protein 2 (OEE 2), and (V) enzyme scavengers of ROS such as catalase, peroxidase, and GST [86, 102, 113, 117, 119].

3.4.2.2 Proteome response to drought stress

Drought means a decreased soil water potential which causes reduced water uptake by roots. Plant response at the molecular level lies in osmotic adjustment, that is, a decrease in osmotic potential of cell cytoplasm due to an enhanced accumulation of several osmolytes and hydrophilic proteins. The primary signal caused by drought is hyperosmotic stress, which is often referred to simply as osmotic stress because a hypo-osmotic condition typically is not a significant problem for plant cells. In leaves, drought leads to stomatal closure associated with reduced CO₂ uptake resulting in imbalances between photosynthetic electron transport processes and carbon assimilation. As a consequence, cellular dehydration is also associated with enhanced ROS formation [120].

Water losing causes decreasing in leaf water potential in contrast with cytoplasmic components concentration and extracellular matrices viscosity increase [121, 122]. In response to drought stress, CO₂ production declines due to stomatal closing. On the other hand, photosynthesis may be known as the first and most significant function negatively affected by water deficiency stress [123, 124].

Decreasing in internal CO₂ concentration impacts on Calvin cycle by disturbing carbon fixation accompanied with a proportional reduction in the activity of various related enzymes like fructose-1,6-biphosphate phosphatase (FBPase), ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), and phosphoribulokinase (PRK). Consequently, glycerate-3-phosphate depletion and NADP⁺ production decline lead to carbohydrate formation decrease in the final step of the Calvin cycle. Moreover, NADP⁺ is the primary electron acceptor in photosystem I (PSI), and therefore O₂ production, lowered as the final production of photosynthesis in plants and excessive generation of reactive oxygen species (ROS) occurs [125, 126, 127, 128]. Moreover, reducing ATP production in response to drought stress is associated with photosynthesis function by negatively affecting the Calvin cycle.

A coordinated down-regulation of the Calvin cycle genes with a decline in carbon fixation in plants exposed to drought stress reduces the energy-wasting for unnecessary biomolecule synthesis through the lower level of carbohydrate production [129].

Under drought stress, due to low CO₂:O₂ ratio ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) enzyme oxygenates ribulose 1,5-bisphosphate (RuBP) and causes photorespiration (C₂ photosynthesis) cycle to function as a carbon recovery system which is correlated with the Calvin cycle [130].

The Krebs cycle (TCA cycle) is one of the primary energy sources for cells and essential for aerobic respiration. There are contradictory reports for effects of drought stress on the Krebs cycle and its intermediate such as PDHA1, NADP-ME, and α-ketoglutaric acid [131, 132, 133].

Another cycle affected by drought stress is the ascorbate-glutathione (ASA-GSH) cycle detoxifies waste hydrogen peroxide (H₂O₂) to H₂O by using antioxidant metabolites like ascorbate, glutathione, and NADPH and the enzymes linking these metabolites [134, 135].

3.4.2.3 Proteome response to temperature stress

Temperature stress (both heat and cold) leads to an imbalance between photosynthetic electron transport processes and carbon assimilation processes resulting in enhanced photoinhibition and thermal energy dissipation [136] and is linked to plant metabolism and performance [137]. The synthesis and accumulation of heat-shock proteins (HSPs) is a prompt response after exposure to extreme temperature stress treatment. It is considered one of the most critical adaptive strategies to overcome the deleterious effects of temperature fluctuation stress [138, 139]. Most HSPs are molecular chaperones involved in protein stabilization and signal transduction during heat stress [140, 141].

Low temperatures (cold and frost) can induce inhibition of water uptake and indirectly result in osmotic stress in cells [142]. Consequently, decreased kinetics of biomolecules leading to reduced cell membrane fluidity and a decreased rate of enzymatic reactions. Frost stress particularly leads to ice crystals in soil, resulting in cellular dehydration [78].

High temperature (heat) stress as enhanced temperature causes enhanced kinetics of biomolecules leading to an enhanced risk of protein misfolding. Thus, plant response includes induction of several heat-shock transcription factors (HSFs) and downstream heat-shock proteins (HSPs). Moreover, heat causes enhanced water evaporation from the soil surface and enhanced leaf transpiration, thus usually resulting in water deficit under field conditions. The heat thus also causes dehydration stress and oxidative stress [136].

4. Conclusions

Plant production in two aspects of quality and quantity plays a key role in food safety and security impressed with global environmental stresses increasing with emphasizing on study to detect plant alterations in response to abiotic stresses. Different levels of plants sense stresses from morphological to molecular aspects however finding deep mechanisms and functions affected by stresses would help to find related genes and biomarkers more accurately. We reviewed the significance of agriculture for our future in addition to its mutual relationship with environment. Climate change as the most effective parameter correlated with food production, is susceptible to impact negatively on both food safety and food security.

Analyzing the proteome profile of plants exposing various types of abiotic stresses including salt, drought and extreme temperature is helpful to find shared and unique mechanisms related to abiotic stresses in addition to finding solution useful for crop production increasing and sustainability.