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The non-essential metalloid arsenic (As) is widely distributed in soil and underground water of many countries. Arsenic contamination is a concern because it creates threat to food security in terms of crop productivity and food safety. Plants exposed to As show morpho-physiological, growth and developmental disorder which altogether result in loss of productivity. At physiological level, As-induced altered biochemistry in chloroplast, mitochondria, peroxisome, endoplasmic reticulum, cell wall, plasma membrane causes reactive oxygen species (ROS) overgeneration which damage cell through disintegrating the structure of lipids, proteins, and DNA. Therefore, plants tolerance to ROS-induced oxidative stress is a vital strategy for enhancing As tolerance in plants. Plants having enhanced antioxidant defense system show greater tolerance to As toxicity. Depending upon plant diversity (As hyperaccumulator/non-hyperaccumulator or As tolerant/susceptible) the mechanisms of As accumulation, absorption or toxicity response may differ. There can be various crop management practices such as exogenous application of nutrients, hormones, antioxidants, osmolytes, signaling molecules, different chelating agents, microbial inoculants, organic amendments etc. can be effective against As toxicity in plants. There is information gap in understanding the mechanism of As-induced response (damage or tolerance response) in plants. This review presents the mechanism of As uptake and accumulation in plants, physiological responses under As stress, As-induced ROS generation and antioxidant defense system response, various approaches for enhancing As tolerance in plants from the available literatures which will make understanding the to date knowledge, knowledge gap and future guideline to be worked out for the development of As tolerant plant cultivars.

Cadmium (Cd) is one of the most threatening soil and water contaminants in agricultural settings. In previous studies, we observed that Cd affects the metabolism and physiology of tomato (Solanum lycopersicum) plants even after short-term exposure. The objective of this research was to use cross-genotype grafting to distinguish between root- and shoot-mediated responses of tomato genotypes with contrasting Cd tolerance at the early stages of Cd exposure. This study provides the first report of organ-specific contributions in two tomato genotypes with contrasting Cd tolerance: Solanum lycopersicum cv. Calabash Rouge and Solanum lycopersicum cv. Pusa Ruby (which have been classified and further characterized as sensitive (S) and tolerant (T) to Cd, respectively). Scion S was grafted onto rootstock S (S/S) and rootstock T (S/T), and scion T was grafted onto rootstock T (T/T) and rootstock S (T/S). A 35 μM cadmium chloride (CdCl

A first insight into the effects of cadmium exposure on the phosphoproteome of tomato plants by performing a comparative analysis of tomato genotypes with contrasting cadmium tolerance.

The current increase in salinity can intensify the disparity between potential and actual crop yields, thus affecting economies and food security. One of the mitigating alternatives is plant breeding via biotechnology, where advances achieved so far are significant. Considering certain aspects when developing studies related to plant breeding can determine the success and accuracy of experimental design. Besides this strategy, halophytes with intrinsic and efficient abilities against salinity can be used as models for improving the response of crops to salinity stress. As crops are mostly glycophytes, it is crucial to point out the molecular differences between these two groups of plants, which may be the key to guiding and optimizing the transformation of glycophytes with halophytic tolerance genes. Therefore, this can broaden perspectives in the trajectory of research towards the cultivation, commercialization, and consumption of salt-tolerant crops on a large scale.

Cadmium (Cd) is a heavy metal considered as one of the main toxic pollutants in the environment and affects several metabolic processes in plants and animals, justifying scientific efforts to study Cd bioremediation and biochemical, physiological, and molecular mechanisms of plant response and tolerance to cope with Cd toxicity. Phytochelatins (PCs) are nonribosomally synthesized small metal-binding peptides, structurally related to the tripeptide glutathione and efficiently induced by Cd in several plant species. Several studies have demonstrated that PCs contribute to the modulation of Cd response and tolerance in plants, in addition to potential applications of PC properties and functions to improve and optimize phytoremediation. The present chapter embodies information on the existing knowledge about direct and indirect contribution of PCs and their synthesis to modulation of Cd tolerance and accumulation in plants, by highlighting studies focused on gene expression, PC isoforms, peptide quantification, and genetic transformation of plants under Cd exposure, besides proteomic studies showing some differentially expressed glutathione metabolism-related proteins.

Cadmium (Cd) is known to be among the most toxic heavy metals to plants, posing severe risks to human health. Understanding Cd response mechanisms can provide insights into obtaining plants to be used for phytoremediation of Cd-contaminated soils and selection of plants with different degrees of Cd tolerance. Metabolites are the end products of cellular regulatory processes and define the cellular phenotype induced by stresses such as Cd toxicity. This chapter aims to summarize the current panorama of research concerning the role of plant metabolites in response to cadmium stress through metabolomic profiling studies as well as studies of preselected compounds in plants exposed to Cd stress.

The present study aimed to investigate the Cd-induced transgenerational effects on plants. Grafted tomato plants, which exhibited the same cultivar as scion and distinct cultivars with contrasting Cd-tolerance as rootstocks, were grown in soil without and with artificial addition of Cd (less than 2.0, and 6.9 mg kg-1 of Cd, respectively) in a pot experiment carried out in a greenhouse. Their fruits were harvested to extract seeds (i.e., the progenies), which were sown over either Cd-free (control) or Cd-containing germitest paper (germination testing paper with 0 and 35 μM of CdCl2, respectively) and grown in a growth chamber. The immediate progeny of all grafting combinations from stressed plants presented an elevated germinability, despite high internal Cd concentration. When sown in Cd-containing germitest paper, the immediate progeny of plants grown in soil with no Cd addition was generally able to maintain or even increase the content of carotenoids and chlorophylls a and b (up to 93.3, 62.8 and 76.1%, respectively), indicating a Cd-induced hormetic effect on photosynthetic pigments. Two of the grafting combinations from stressed plants yielded seeds that generated seedlings with enhanced dry mass when they were sown in Cd-free media (~41%), suggesting a Cd-induced transgenerational enhancement of biomass production. Because only one tomato cultivar was used as scion, data indicated that type and degree of Cd-induced transgenerational effects depend strongly on signals generated and/or processed in roots of the parental plants. When sown in Cd-contaminated germitest paper, the immediate progeny of Cd-treated plants presented major reductions in the leaf area (35-69%) and content of photosynthetic pigments (57-93%) in comparison to the progeny from control plants. However, one of the grafting combinations exhibited satisfactory performance after "double" exposure to Cd, showing 91% of the biomass that was produced in the seedlings of control seeds from control plants. Further investigation indicated that adjustments in the chlorophyll fluorescence behavior might counterbalance losses in leaf pigments and area. Taken together, our data provide new insights on the origin, outcomes and mode of action of the Cd-induced transgenerational effects.

Plants are subjected to a wide variety of abiotic and biotic stresses, which have been responsible for huge yield losses worldwide. Among abiotic stresses, drought, high salinity and extremes of temperature comprise some of the major factors reducing the agricultural production. On the other hand, plants have evolved several mechanisms of response and adaptation to adverse conditions. In order to overcome abiotic stress conditions, insights about physiological components that contribute to endogenous defense mechanisms of plants are extremely relevant. Genes coding for NAC transcription factors have been identified from various plant species. NAC proteins are related to several roles at cellular level in improvement of plants against abiotic stresses. This review aims to summarize current knowledge about the interaction of NAC proteins with cis-acting regulatory elements that function in abiotic stress-responsive gene expression, as well as the regulation of these proteins by plant hormones. Also, we present recent progress revealing the importance of differential expression of theses transcriptional regulators in tolerance against abiotic stresses in genetically transformed plants.

Cadmium (Cd) is a heavy metal highly toxic to plants and human and animal health. The increased concentration of this metal in the environment in recent decades is the result of anthropogenic activities that include the production of mineral fertilizers, pesticides, intense mining, waste disposal, and foundries. Cd accumulation is known to induce oxidative stress in plant cells due to overproduction of reactive oxygen species, which may result in severe damage at the cellular level, ultimately impairing plant growth and productivity. In response to such stress, different molecules having enzymatic or nonenzymatic actions contribute to mitigate plant cellular damage and balance redox homeostasis in plant cells. This chapter aims to summarize current knowledge about the prospecting of important components of the molecular mechanisms associated with antioxidant machinery in plant response and tolerance to Cd toxicity. Insights into antioxidant response regulation, which includes hormones, signaling molecules, transcription factors, and microRNAs, are also presented.

The increase in global population is a threat to the food supply. In addition, the decline in agricultural investment has also decreased the global food supply. Competition for land means that there is a need to increase agricultural productivity; however, the growth and yield of plants are greatly influenced by environmental stresses once crops are sessile. Furthermore, global climate changes can also compromise food security, thus increased tolerance to these stresses is important. It is estimated that less than 10% of the soils used in agriculture are free from environmental stresses. In the last 30 years new methodologies have been developed to allow the production of genetically modified crops with improved tolerance to abiotic stresses. These modified crops are not only able to survive stress, but they also show good yields under stress conditions. Abiotic stress tolerance genes can be separated into those with unique or regulatory actions. The first category contains genes that encode osmoprotectants, LEA proteins, transport proteins, lipid biosynthesis proteins, heat shock proteins, and detoxifying proteins. The second category contains genes that encode signal transduction and transcription factors. This chapter aims to present recent studies regarding genetically engineered crops to abiotic stress resistance, specifically highlighting the main food sources.

The TCTP (Translationally controlled tumor protein) is a highly conserved protein family found in eukaryotic organisms, which has been associated to the performance of several functions at the cellular level, as those related to growth, development, and responses against environmental stresses. However, studies on TCTP from plants are still incipient. Cassava (Manihot esculenta Crantz) is a crop of great socioeconomic importance for millions of people in the world, especially because of its high energy content. Previous studies reported the identification of a cassava TCTP (MeTCTP) with potential roles in storage root formation and salt stress response. Here, our main goal was to increase the understanding about the roles of MeTCTP in response to abiotic stresses. We verified that the overexpression of recombinant MeTCTP in Escherichia coli increased tolerance of bacterial cells to heat stress. In addition, the recombinant MeTCTP was purified by nickel affinity and evaluated by chaperone activity assays, which showed its ability to preserve the function of NdeI restriction enzyme under thermal denaturation conditions. Results presented here provided insights into the relationship of MeTCTP with responses of plants to abiotic stresses

Climate change is a major global concern that can make agriculture even more risk prone, especially in the developing world. The water deficit of soil causes environmental problems, limiting plant survival, growth, and productivity. However, some plants can use certain strategies to resist drought stresses. Adaptations to drought involve metabolic and morphological alterations to prevent injury to plants. Underlying these several kinds of alterations are molecular mechanisms that regulate the expression of genes involved in the various adaptive processes. Drought tolerance has been achieved using genetic engineering strategies to improve water-use efficiency of plants, cell protection mechanisms against ROS, and hormonal balance to alter the growth and development in order to avoid drought and change the expression of drought-induced transcription factors that act as master switches in regulating a large number of downstream drought-response genes. Various genes are induced in response to drought at the transcriptional level, and these gene products have main roles in tolerance to drought. Understanding the molecular mechanisms in drought response is important for improvement of drought tolerance using molecular techniques. Some of the genes that will probably upregulated under drought stress conditions include the genes involved in osmolyte synthesis, genes coding for LEA proteins, aquaporins, signaling molecules, and transcription factors. Studies of contrasting crop genotypes or genetic engineering of crops help in differentiating responses to drought from those leading to drought tolerance. The specific importance to crop plants is not whether they survive stress, but whether they show significant yields under stress conditions.

Late embryogenesis abundant (LEA) proteins are small molecular weight proteins involved in acquisition of tolerance to drought, salinity, high temperature, cold, and freezing stress in many plants. Previous studies revealed a cDNA sequence coding for a 10 kDa atypical LEA protein, named MeLEA3, predicted to be located into mitochondria with potential role in salt stress response of cassava (Manihot esculenta Crantz). Here we aimed to produce the recombinant MeLEA3 protein by heterologous expression in Escherichia coli and evaluate the tolerance of bacteria expressing this protein under abiotic stress. Our result revealed that the recombinant MeLEA3 protein conferred a protective function against heat and salt stress in bacterial cells. Also, the recombinant MeLEA3 protein showed in vitro chaperone activity by protection of NdeI restriction enzyme activity under heat stress.