From Genes to Stress Response: Genomic and Transcriptomic Data Suggest the Significance of the Inositol and Raffinose Family Oligosaccharide Pathways in Stylosanthes scabra, Adaptation to the Caatinga Environment.

S. scabra is an important forage and extremophilic plant native to the Brazilian Caatinga semiarid region. It has only recently been subjected to omics-based investigations, and the generated datasets offer insights into biotechnologically significant candidates yet to be thoroughly examined. INSs (inositol and its derivatives) and RFO (raffinose oligosaccharide family) pathways emerge as pivotal candidates, given their critical roles in plant physiology. The mentioned compounds have also been linked to negative impacts on the absorption of nutrients in mammals, affecting overall nutritional intake and metabolism. Therefore, studying these metabolic pathways is important not just for plants but also for animals who depend on them as part of their diet. INS and RFO pathways in S. scabra stood out for their abundance of identified loci and enzymes. The enzymes exhibited genomic redundancy, being encoded by multiple loci and various gene families. The phylogenomic analysis unveiled an expansion of the PIP5K and GolS gene families relative to the immediate S. scabra ancestor. These enzymes are crucial for synthesizing key secondary messengers and the RFO precursor, respectively. Transcriptional control of the studied pathways was associated with DOF-type, C2H2, and BCP1 transcription factors. Identification of biological processes related to INS and RFO metabolic routes in S. scabra highlighted their significance in responding to stressful conditions prevalent in the Caatinga environment. Finally, RNA-Seq and qPCR data revealed the relevant influence of genes of the INS and RFO pathways in the S. scabra response to water deprivation. Our study deciphers the genetics and transcriptomics of the INS and RFO in S. scabra, shedding light on their importance for a Caatinga-native plant and paving the way for future biotechnological applications in this species and beyond.

Growth, Productivity, Yield Components and Seasonality of Different Genotypes of Forage Clover Lotus corniculatus L. under Varied Soil Moisture Contents.

This study aimed to evaluate the response to water deficit of different ecotypes and a variety of Lotus corniculatus on growth, productivity, and yield components, through seasonal times. A randomized block experimental design in a 2 × 5 factorial arrangement with three replicates was used. The first variation factor was soil moisture contents: field capacity (FC) was 26.5% ± 1.5, and water deficit (WD) was 85% of FC (22.5% ± 1.5); the second variation factor was the ecotypes identified with the codes 255301, 255305, 202700 and 226792 and of the variety Estanzuela Ganador. The best responses in plant cover and weight of accumulated fresh biomass were obtained in the ecotype 202700 under WD, with values of 1649.0 cm2 and 583.7 g plant-1, and 1661.2 cm2 and 740.1 g plant-1 in ecotype 255305 under FC. The leaf clover was the main component of yield during the summer and autumn seasons. Ecotype 226792 was tolerant to low temperatures during the winter season with better leaf development. Ecotype 202700 is the best option for forage clover production when water is limited, and ecotype 255305 when water is not resource-limited, but these preliminary conclusions need to be confirmed in field studies.

From genes to ecosystems: Decoding plant tolerance mechanisms to arsenic stress.

Arsenic (As), a metalloid of considerable toxicity, has become increasingly bioavailable through anthropogenic activities, raising As contamination levels in groundwater and agricultural soils worldwide. This bioavailability has profound implications for plant biology and farming systems. As can detrimentally affect crop yield and pose risks of bioaccumulation and subsequent entry into the food chain. Upon exposure to As, plants initiate a multifaceted molecular response involving crucial signaling pathways, such as those mediated by calcium, mitogen-activated protein kinases, and various phytohormones (e.g., auxin, methyl jasmonate, cytokinin). These pathways, in turn, activate enzymes within the antioxidant system, which combat the reactive oxygen/nitrogen species (ROS and RNS) generated by As-induced stress. Plants exhibit a sophisticated genomic response to As, involving the upregulation of genes associated with uptake, chelation, and sequestration. Specific gene families, such as those coding for aquaglyceroporins and ABC transporters, are key in mediating As uptake and translocation within plant tissues. Moreover, we explore the gene regulatory networks that orchestrate the synthesis of phytochelatins and metallothioneins, which are crucial for As chelation and detoxification. Transcription factors, particularly those belonging to the MYB, NAC, and WRKY families, emerge as central regulators in activating As-responsive genes. On a post-translational level, we examine how ubiquitination pathways modulate the stability and function of proteins involved in As metabolism. By integrating omics findings, this review provides a comprehensive overview of the complex genomic landscape that defines plant responses to As. Knowledge gained from these genomic and epigenetic insights is pivotal for developing biotechnological strategies to enhance crop As tolerance.

Advancing abiotic stress monitoring in plants with a wearable non-destructive real-time salicylic acid laser-induced-graphene sensor.

Drought and salinity stresses present significant challenges that exert a severe impact on crop productivity worldwide. Understanding the dynamics of salicylic acid (SA), a vital phytohormone involved in stress response, can provide valuable insights into the mechanisms of plant adaptation to cope with these challenging conditions. This paper describes and tests a sensor system that enables real-time and non-invasive monitoring of SA content in avocado plants exposed to drought and salinity. By using a reverse iontophoretic system in conjunction with a laser-induced graphene electrode, we demonstrated a sensor with high sensitivity (82.3 nA/[µmol L-1⋅cm-2]), low limit of detection (LOD, 8.2 µmol L-1), and fast sampling response (20 s). Significant differences were observed between the dynamics of SA accumulation in response to drought versus those of salt stress. SA response under drought stress conditions proved to be faster and more intense than under salt stress conditions. These different patterns shed light on the specific adaptive strategies that avocado plants employ to cope with different types of environmental stressors. A notable advantage of the proposed technology is the minimal interference with other plant metabolites, which allows for precise SA detection independent of any interfering factors. In addition, the system features a short extraction time that enables an efficient and rapid analysis of SA content.

Decreased Photosynthetic Efficiency in Nicotiana tabacum L. under Transient Heat Stress.

Heat stress is an abiotic factor that affects the photosynthetic parameters of plants. In this study, we examined the photosynthetic mechanisms underlying the rapid response of tobacco plants to heat stress in a controlled environment. To evaluate transient heat stress conditions, changes in photochemical, carboxylative, and fluorescence efficiencies were measured using an infrared gas analyser (IRGA Licor 6800) coupled with chlorophyll a fluorescence measurements. Our findings indicated that significant disruptions in the photosynthetic machinery occurred at 45 °C for 6 h following transient heat treatment, as explained by 76.2% in the principal component analysis. The photosynthetic mechanism analysis revealed that the dark respiration rate (Rd and Rd*CO2) increased, indicating a reduced potential for carbon fixation during plant growth and development. When the light compensation point (LCP) increased as the light saturation point (LSP) decreased, this indicated potential damage to the photosystem membrane of the thylakoids. Other photosynthetic parameters, such as AMAX, VCMAX, JMAX, and ΦCO2, also decreased, compromising both photochemical and carboxylative efficiencies in the Calvin-Benson cycle. The energy dissipation mechanism, as indicated by the NPQ, qN, and thermal values, suggested that a photoprotective strategy may have been employed. However, the observed transitory damage was a result of disruption of the electron transport rate (ETR) between the PSII and PSI photosystems, which was initially caused by high temperatures. Our study highlights the impact of rapid temperature changes on plant physiology and the potential acclimatisation mechanisms under rapid heat stress. Future research should focus on exploring the adaptive mechanisms involved in distinguishing mutants to improve crop resilience against environmental stressors.

Sulfate supply decreases barium availability, uptake, and toxicity in lettuce plants grown in a tropical Ba-contaminated soil.

Barium (Ba) is a non-essential element that can cause toxicity in living organisms and environmental contamination. Plants absorb barium predominantly in its divalent cationic form Ba2+. Sulfur (S) can decrease the availability of Ba2+ in the soil by causing its precipitation as barium sulfate, a compound known for its very low solubility. The objective of this study was to evaluate the effect of soil sulfate supply in soil Ba fractions, as well as on plant growth, and Ba and S uptake by lettuce plants grown in artificially Ba-contaminated soil under greenhouse conditions. The treatments consisted of five Ba doses (0, 150, 300, 450, and 600 mg kg-1 Ba, as barium chloride) combined with three S doses (0, 40, and 80 mg kg-1 S, as potassium sulfate). The treatments were applied to soil samples (2.5 kg) and placed in plastic pots for plant cultivation. The Ba fractions analyzed were extractable-Ba, organic matter-Ba, oxides associated-Ba, and residual-Ba. The results indicate that the extractable-Ba fraction was the main one responsible for Ba bioavailability and phytotoxicity, probably corresponding to the exchangeable Ba in the soil. The dose of 80 mg kg-1 of S reduced extractable-Ba by 30% at higher Ba doses while it increased the other fractions. Furthermore, S supply attenuated the growth inhibition in plants under Ba exposure. Thus, S supply protected the lettuce plants from Ba toxicity by reduction of Ba availability in soil and plant growth enhancement. The results suggest that sulfate supply is a suitable strategy for managing Ba-contaminated areas.

Metabolism of guarana (Paullinia cupana Kunth var. sorbilis) plants and fruit production subjected to glyphosate doses.

Guarana (Paullinia cupana Kunth var. sorbilis) is a typically Amazonian plant of high economic value due to the compounds found in its seed. For guarana to reach the maximum productive potential, management practices such as weed control are necessary. The use of herbicides is a viable alternative, however, its drift may lead to adverse effects on the primary and secondary plant metabolisms and cause losses in crop production. This study evaluated the differential drift effects of glyphosate doses on the physiology of guarana plants and the production of compounds of economic interest in their seeds. Glyphosate doses (57.6, 115.2, 230.4, 460.8 g ae ha-1) were applied to adult guarana plants after the flowering period. The photosynthetic functions and metabolism effects were evaluated. Herbicide treatments led to oxidative stress due to increased lipid peroxidation and increased carbohydrate and amino acid in their leaflets. Despite this, glyphosate showed no effect on fruit production or the content of secondary metabolites of commercial interest in seeds.

Stromal Ascorbate Peroxidase (OsAPX7) Modulates Drought Stress Tolerance in Rice (Oryza sativa).

Chloroplast ascorbate peroxidases exert an important role in the maintenance of hydrogen peroxide levels in chloroplasts by using ascorbate as the specific electron donor. In this work, we performed a functional study of the stromal APX in rice (OsAPX7) and demonstrated that silencing of OsAPX7 did not impact plant growth, redox state, or photosynthesis parameters. Nevertheless, when subjected to drought stress, silenced plants (APX7i) show a higher capacity to maintain stomata aperture and photosynthesis performance, resulting in a higher tolerance when compared to non-transformed plants. RNA-seq analyses indicate that the silencing of OsAPX7 did not lead to changes in the global expression of genes related to reactive oxygen species metabolism. In addition, the drought-mediated induction of several genes related to the proteasome pathway and the down-regulation of genes related to nitrogen and carotenoid metabolism was impaired in APX7i plants. During drought stress, APX7i showed an up-regulation of genes encoding flavonoid and tyrosine metabolism enzymes and a down-regulation of genes related to phytohormones signal transduction and nicotinate and nicotinamide metabolism. Our results demonstrate that OsAPX7 might be involved in signaling transduction pathways related to drought stress response, contributing to the understanding of the physiological role of chloroplast APX isoforms in rice.

Growth and functional leaf traits of coppice regrowth of Bertholletia excelsa during an El Niño event in the central Amazon / Crescimento e características funcionais foliares de rebrotas de Bertholletia excelsa durante um evento de El Niño na Amazônia Central

The most severe drought of this century in the Amazon rainforest, which was caused by El Niño, occurred from 2015 to 2016. With a focus on the ecophysiology of the regrowth of the Brazil nut tree, Bertholletia excelsa, it was investigated how the progression of the drought of 2015-2016 affected the physiological traits of the coppice regrowth of B. excelsa. The experiment was carried out in a ten-year-old plantation of Brazil nut trees, which had been subjected to thinning and coppice regrowth two years earlier. In the sprouts grown on the stumps of cut trees, the following treatments were applied: (T1) thinning to one sprout per stump; (T2) thinning to two sprouts per stump, and (T3) maintenance of three sprouts per stump. Thinning treatments did not alter the growth and ecophysiological traits of the Brazil nut tree sprouts, though the phosphorus content of the leaves was higher in T1. However, the progression of the drought in 2015-2016 negatively affected the growth (height) and gas exchange of sprouts of all treatments. In addition, an increase of around 37% was observed in the intrinsic wateruse efficiency. Concerning photochemical performance, no alterations were observed. Therefore, drought stress promoted a negative effect on sprout growth and affected traits related to the photosynthesis of the B. excelsa sprouts independently of the number of sprouts per stump.(AU)

A seca mais severa deste século na floresta amazônica, causada por El Niño, ocorreu de 2015 a 2016. Com foco na ecofisiologia da rebrota da castanheira da Amazônia, foi investigado como a progressão da seca de 2015-2016 afetou as características fisiológicas das rebrotas de uma talhadia de B. excelsa. O experimento foi realizado em uma plantação de castanheiras com dez anos, a qual havia sido submetida a um desbaste e rebrota de talhadia dois anos antes. Nas rebrotas crescidas sobre os tocos das árvores cortadas foram aplicados os seguintes tratamentos: (T1) desbrota para manter um broto por cepa; (T2) desbrota para manter dois brotos por cepa; e (T3) manutenção de três brotos por cepa. Os tratamentos de desbrota não alteraram o crescimento e as características ecofisiológicas dos brotos da castanheira, exceto para o teor foliar de fósforo, que foi maior em T1. Porém, a progressão da seca em 2015-2016 afetou negativamente o crescimento em altura e as trocas gasosas dos brotos de todos os tratamentos. Além disso, foi observado um aumento de cerca de 37% na eficiência intrínseca do uso da água. Quanto ao desempenho fotoquímico, não foram observadas alterações. Portanto, o estresse hídrico promoveu efeito negativo no crescimento da brotação e afetou características relacionadas à fotossíntese das brotações de B. excelsa, independentemente do número de brotações por cepa.(AU)

Strawberry Biostimulation: From Mechanisms of Action to Plant Growth and Fruit Quality.

The objective of this review is to present a compilation of the application of various biostimulants in strawberry plants. Strawberry cultivation is of great importance worldwide, and, there is currently no review on this topic in the literature. Plant biostimulation consists of using or applying physical, chemical, or biological stimuli that trigger a response-called induction or elicitation-with a positive effect on crop growth, development, and quality. Biostimulation provides tolerance to biotic and abiotic stress, and more absorption and accumulation of nutrients, favoring the metabolism of the plants. The strawberry is a highly appreciated fruit for its high organoleptic and nutraceutical qualities since it is rich in phenolic compounds, vitamins, and minerals, in addition to being a product with high commercial value. This review aims to present an overview of the information on using different biostimulation techniques in strawberries. The information obtained from publications from 2000-2022 is organized according to the biostimulant's physical, chemical, or biological nature. The biochemical or physiological impact on plant productivity, yield, fruit quality, and postharvest life is described for each class of biostimulant. Information gaps are also pointed out, highlighting the topics in which more significant research effort is necessary.

Reactive Oxygen, Nitrogen, and Sulfur Species (RONSS) as a Metabolic Cluster for Signaling and Biostimulation of Plants: An Overview.

This review highlights the relationship between the metabolism of reactive oxygen species (ROS), reactive nitrogen species (RNS), and H2S-reactive sulfur species (RSS). These three metabolic pathways, collectively termed reactive oxygen, nitrogen, and sulfur species (RONSS), constitute a conglomerate of reactions that function as an energy dissipation mechanism, in addition to allowing environmental signals to be transduced into cellular information. This information, in the form of proteins with posttranslational modifications or signaling metabolites derived from RONSS, serves as an inducer of many processes for redoxtasis and metabolic adjustment to the changing environmental conditions to which plants are subjected. Although it is thought that the role of reactive chemical species was originally energy dissipation, during evolution they seem to form a cluster of RONSS that, in addition to dissipating excess excitation potential or reducing potential, also fulfils essential signaling functions that play a vital role in the stress acclimation of plants. Signaling occurs by synthesizing many biomolecules that modify the activity of transcription factors and through modifications in thiol groups of enzymes. The result is a series of adjustments in plants' gene expression, biochemistry, and physiology. Therefore, we present an overview of the synthesis and functions of the RONSS, considering the importance and implications in agronomic management, particularly on the biostimulation of crops.

Roles of Calcium Signaling in Gene Expression and Photosynthetic Acclimatization of Solanum lycopersicum Micro-Tom (MT) after Mechanical Damage.

A momentary increase in cytoplasmic Ca2+ generates an oscillation responsible for the activation of proteins, such as calmodulin and kinases, which interact with reactive oxygen species (ROS) for the transmission of a stress signal. This study investigated the influence of variations in calcium concentrations on plant defense signaling and photosynthetic acclimatization after mechanical damage. Solanum lycopersicum Micro-Tom was grown with 0, 2 and 4 mM Ca2+, with and without mechanical damage. The expression of stress genes was evaluated, along with levels of antioxidant enzymes, hydrogen peroxide, lipid peroxidation, histochemistry, photosynthesis and dry mass of organs. The ROS production generated by mechanical damage was further enhanced by calcium-free conditions due to the inactivation of the oxygen evolution complex, contributing to an increase in reactive species. The results indicated that ROS affected mechanical damage signaling because calcium-free plants exhibited high levels of H2O2 and enhanced expression of kinase and RBOH1 genes, necessary conditions for an efficient response to stress. We conclude that the plants without calcium supply recognized mechanical damage but did not survive. The highest expression of the RBOH1 gene and the accumulation of H2O2 in these plants signaled cell death. Plants grown in the presence of calcium showed higher expression of SlCaM2 and control of H2O2 concentration, thus overcoming the stress caused by mechanical damage, with photosynthetic acclimatization and without damage to dry mass production.

Abiotic Stresses in Plants and Their Markers: A Practice View of Plant Stress Responses and Programmed Cell Death Mechanisms.

Understanding how plants cope with stress and the intricate mechanisms thereby used to adapt and survive environmental imbalances comprise one of the most powerful tools for modern agriculture. Interdisciplinary studies suggest that knowledge in how plants perceive, transduce and respond to abiotic stresses are a meaningful way to design engineered crops since the manipulation of basic characteristics leads to physiological remodeling for plant adaption to different environments. Herein, we discussed the main pathways involved in stress-sensing, signal transduction and plant adaption, highlighting biochemical, physiological and genetic events involved in abiotic stress responses. Finally, we have proposed a list of practice markers for studying plant responses to multiple stresses, highlighting how plant molecular biology, phenotyping and genetic engineering interconnect for creating superior crops.

Overexpression of the Tectona grandis TgNAC01 regulates growth, leaf senescence and confer salt stress tolerance in transgenic tobacco plants.

NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized in Tectona grandis (teak), one of the hardwood trees of highest economic importance in the world. In this work, we characterized the novel TgNAC01 gene, which is involved in signaling pathways that mediate teak response to stress. Abscisic acid (ABA) increases TgNAC01 expression in teak plants. Therefore, this gene may have a role in signaling events that mediate ABA-dependent osmotic stress responsive in this plant species. Stable expression in tobacco plants showed that the TgNAC01 protein is localized in the cell nucleus. Overexpression of TgNAC01 in two out three independent transgenic tobacco lines resulted in increased growth, leaf senescence and salt tolerance compared to wild type (WT) plants. Moreover, the stress tolerance of transgenic plants was affected by levels of TgNAC01 gene expression. Water potential, gas exchange and chlorophyll fluorescence were used to determine salt stress tolerance. The 35S:TgNAC01-6 line under 300 mM NaCl stress responded with a significant increase in photosynthesis rate, stomatal conductance, transpiration and carboxylation efficiency, but lower water potential compared to WT plants. The data indicate that the TgNAC01 transcription factor acts as a transcriptional activator of the ABA-mediated regulation and induces leaf senescence.

Changes in galling insect community on Caryocar brasiliense trees mediated by soil chemical and physical attributes / Mudanças na comunidade de insetos galhadores em plantas de Caryocar brasiliense mediadas por atributos químicos e físicos do solo

The nutrient stress hypothesis predicts that galling insects prevail on host plants growing in habitats with soils of low nutritional quality. Caryocar brasiliense (Caryocaraceae) is host to four different leaf-galling insects. These insects have the potential to cause a reduction in the production of C. brasiliense fruits, an important source of income for many communities in Brazil. We studied the effects of soil physical and chemical characteristics on the abundance, species richness, and diversity of galling insects and their natural enemies on C. brasiliense trees growing under three different soil conditions. Our data corroborate the hypothesis that in nutritionally poor (e.g., lower phosphorus content) and worse physical textures (e.g., sandy) soils, host plants support higher species richness and diversity of galling insects. However, the abundance of Eurytoma sp. (the most common gall in C. brasiliense), was correlated with a higher phosphorus concentration in the soil (better nutritional condition). The percentage of galled leaflets and the area of leaflets occupied by Eurytoma sp galls were higher in the more fertile soil. In this soil, there was greater abundance, species richness, and diversity of parasitoids of Eurytoma sp. (e.g., Sycophila sp.) and predators (e.g., Zelus armillatus). Our data indicate the importance of habitat quality in the composition of the galling insect community and the impact of soil properties in mediating the distribution of these insects in C. brasiliense.

A hipótese de estresse nutricional prevê que insetos galhadores prevalecem em plantas hospedeiras que crescem em habitats com solos de baixa qualidade nutricional. Caryocar brasiliense (Caryocaraceae) é hospedeiro de quatro diferentes espécies de insetos galhadores. Estes insetos têm potencial para afetar a produção dos frutos de C. brasiliense, uma importante fonte de renda para muitas comunidades no Brasil. Neste trabalho, estudamos os efeitos das características físicas e químicas do solo sobre a abundância, riqueza e diversidade de espécies de insetos galhadores e seus inimigos naturais. O estudo foi realizado em plantas de C. brasiliense em três diferentes condições de solo. Nossos dados corroboram a hipótese de que, em solos nutricionalmente pobres (por exemplo, menor teor de fósforo) e de texturas físicas piores (por exemplo, arenoso) as plantas hospedeiras suportam maior riqueza e diversidade de espécies de insetos galhadores. No entanto, a abundância de Eurytoma sp. (galhador mais comum em C. brasiliense), foi correlacionada com maior concentração de fósforo no solo (melhor condição nutricional). A porcentagem de folíolos da planta hospedeira galhada e a área de folíolos ocupada por galhas de Eurytoma sp foi maior no solo mais fértil. Neste solo, houve maior abundância, riqueza de espécies e diversidade de parasitóides de Eurytoma sp. (por exemplo, Sycophila sp.) e predadores (por exemplo, Zelus armillatus). Nossos dados indicam a importância da qualidade do habitat na composição da comunidade de insetos galhadores e o impacto das propriedades do solo na mediação da distribuição desses insetos em C. brasiliense.

Biostimulation and toxicity: The magnitude of the impact of nanomaterials in microorganisms and plants.

Background: Biostimulation and toxicity constitute the continuous response spectrum of a biological organism against physicochemical or biological factors. Among the environmental agents capable of inducing biostimulation or toxicity are nanomaterials. On the < 100 nm scale, nanomaterials impose both physical effects resulting from the core's and corona's surface properties, and chemical effects related to the core's composition and the corona's functional groups. Aim of Review: The purpose of this review is to describe the impact of nanomaterials on microorganisms and plants, considering two of the most studied physical and chemical properties: size and concentration. Key Scientific Concepts of Review: Using a graphical analysis, the presence of a continuous biostimulation-toxicity spectrum is shown considering different biological responses. In microorganisms, the results showed high susceptibility to nanomaterials. Simultaneously, in plants, a hormetic response was found related to nanomaterials concentration and, in a few cases, a positive response in the smaller nanomaterials when these were applied at a higher level. With the above, it is concluded that: (1) microorganisms are more susceptible to nanomaterials than plants, (2) practically all nanomaterials seem to induce responses from biostimulation to toxicity in plants, and (3) the kind of response observed will depend in a complex way on the nanomaterials physical and chemical characteristics, of the biological species with which they interact, and of the form and route of application and on the nature of the medium -soil, soil pore water, and biological surfaces- where the interaction occurs.

Cadmium uncouples mitochondrial oxidative phosphorylation and induces oxidative cellular stress in soybean roots.

Cadmium (Cd) inhibits soybean root growth, but its exact mode of action is still not completely understood. We evaluated the effects of Cd on growth, mitochondrial respiration, lipid peroxidation, total phenols, glutathione, and activities of lipoxygenase (LOX), superoxide dismutase (SOD), and catalase (CAT) in soybean roots. In primary roots, Cd stimulated KCN-insensitive respiration and KCN-SHAM-insensitive respiration, indicating the involvement of the alternative oxidase (AOX) pathway, while it decreased KCN-sensitive respiration, suggesting an inhibition of the cytochrome oxidase pathway (COX). In isolated mitochondria, Cd uncoupled the oxidative phosphorylation since it decreased state III respiration (coupled respiration) and ADP/O and respiratory control ratios, while it increased state IV respiration (depletion of exogenously added ADP). The uncoupling effect increased extramitochondrial LOX activity, lipid peroxidation, and oxidized and reduced glutathione, which induced an antioxidant response with enhanced SOD and CAT activities. In brief, our findings reveal that Cd acts as an uncoupler of the mitochondrial oxidative phosphorylation in soybean roots, disturbing cellular respiration and inducing oxidative cellular stress.

Water Deprivation Induces Biochemical Changes Without Reduction in the Insecticidal Activity of Maize and Soybean Transgenic Plants.

Like conventional crops, transgenic plants expressing insecticidal toxins from Bacillus thuringiensis (Bt) are subjected to water deprivation. However, the effects of water deprivation over the insecticidal activity of Bt plants are not well understood. We submitted Bt maize and Bt soybean to water deprivation and evaluated biochemical stress markers and the insecticidal activity of plants against target insects. Bt maize (DAS-Ø15Ø7-1 × MON-89Ø34-3 × MON-ØØ6Ø3-6 × SYN-IR162-4) containing the PowerCore Ultra traits, Bt soybean (DAS-444Ø6-6 × DAS-81419-2) with the Conkesta E3 traits, and commercial non-Bt cultivars were cultivated and exposed to water deprivation in the greenhouse. Leaves were harvested for quantification of hydrogen peroxide, malondialdeyde (MDA), and total phenolics and insecticidal activity. Maize or soybean leaf disks were used to evaluate the insecticidal activity against, respectively, Spodoptera frugiperda (J.E Smith) and Chrysodeixis includens (Walker) neonates. Except for Bt soybean, water deprivation increased hydrogen peroxide and MDA contents in Bt and non-Bt plants. Both biochemical markers of water deficit were observed in lower concentrations in Bt plants than in non-Bt commercial cultivars. Water deprivation did not result in changes of phenolic contents in Bt and non-Bt maize. For Bt or non-Bt soybean, phenolic contents were similar despite plants being exposed or not to water deprivation. Water deprivation did not alter substantially insect survival in non-Bt maize or non-Bt soybean. Despite water deprivation-induced biochemical changes in plants, both Bt plants maintained their insecticidal activity (100% mortality) against the target species.

Effect of light stress on Crotalaria spectabilis (Fabaceae) and on its herbivore insect, the moth Utetheisa ornatrix (Erebidae: Arctiinae) / Efeito do estresse luminoso sobre Crotalaria spectabilis (Fabaceae) e seu inseto herbívoro, a mariposa Utetheisa ornatrix (Erebidae: Arctiinae)

The Plant Stress Hypothesis predicts that stressed plants are more attacked by herbivorous insects. In this work, we investigated the influence of light stress on Crotalaria spectabilis Roth (Fabaceae) and on its main herbivore, the moth Utetheisa ornatrix (L., 1758) (Erebidae: Arctiinae). Specifically, we verified whether plants stressed by shading differ from non-stressed plants in terms of productivity, morphological characteristics and water percentage. We also evaluated the performance of moths in stressed and non-stressed plants. Seeds were sown in pots. When the plants reached 50 cm in height, they were randomly divided into two groups: stressed plants (treatment group) and non-stressed plants (control group). The stressed plants were covered by a black mesh, providing 50% of shading. Eight characteristics of stressed and non-stressed C. spectabilis plants were evaluated: height, fresh and dry aerial biomass, number of pods and seeds, leaf hardness, number of trichomes, leaf area, specific leaf mass and percentage of leaf water. Moths were raised individually on leaves of stressed and non-stressed plants and we obtained the larval survival, larval development time, pupal weight and female fecundity. The non-stressed plants had significantly higher percentage of water in the leaves, greater fresh aerial biomass and a higher number of trichomes than the stressed plants. The survival rate was 98% for larvae raised on leaves from stressed plants and 92% on leaves from non-stressed plants. The larval developmental time was significantly shorter and the weight of female pupae significantly higher in non-stressed plants than in stressed plants. Thus, the Plant Stress Hypothesis was only corroborated by two tested variables: number of trichomes (lower in stressed plants) and larval survival (higher in stressed plants). Trichomes are among the main types of plant defenses against herbivory and reducing their number on leaves would make stressed plants more susceptible to attack by moth larvae, a fact corroborated by a greater larval survival. One of the possible explanations for the lack of corroboration of the Plant Stress Hypothesis for most of the variables tested is that other characteristics can be changed under stress conditions, such as the concentration of secondary compounds.(AU)

Efeito do estresse luminoso sobre Crotalaria spectabilis (Fabaceae) e seu inseto herbívoro, a mariposa Utetheisa ornatrix (Erebidae:Arctiinae) A hipótese do estresse da planta prevê que as plantas estressadas são mais atacadas por insetos herbívoros. Neste trabalho, investigamos a influência do estresse luminoso em Crotalaria spectabilis Roth (Fabaceae) e em seu principal herbívoro, a mariposa Utetheisa ornatrix (L., 1758) (Erebidae: Arctiinae). Especificamente, verificamos se as plantas estressadas por sombreamento diferem das plantas não estressadas em termos de produtividade, características morfológicas e porcentagem de água. Também avaliamos o desempenho das mariposas em plantas estressadas e não estressadas. As sementes foram semeadas em vasos. Quando as plantas atingiram 50 cm de altura, foram divididas aleatoriamente em dois grupos: plantas estressadas (grupo de tratamento) e plantas sem estresse (grupo controle). As plantas estressadas foram cobertas por uma malha preta, proporcionando 50% de sombreamento. Foram avaliadas oito características de plantas estressadas e não estressadas de C. spectabilis: altura, biomassa aérea fresca e seca, número de vagens e sementes, dureza foliar, número de tricomas, área foliar, massa foliar específica e porcentagem de água foliar. As mariposas foram criadas individualmente em folhas de plantas estressadas e não estressadas. Obtivemos a sobrevivência larval, o tempo de desenvolvimento larval, o peso pupal e a fecundidade das fêmeas. As plantas não estressadas apresentaram porcentagem significativamente maior de água nas folhas, maior biomassa aérea fresca e um maior número de tricomas do que as plantas estressadas. A taxa de sobrevivência foi de 98% para larvas criadas em folhas de plantas sob estresse e 92% em folhas de plantas sem estresse. O tempo de desenvolvimento larval foi significativamente menor e o peso das pupas femininas significativamente maior em plantas sem estresse do que em plantas estressadas. Assim, a hipótese de estresse em plantas foi corroborada apenas por duas variáveis testadas: número de tricomas (menor nas plantas estressadas) e sobrevivência larval (maior nas plantas estressadas). Os tricomas estão entre os principais tipos de defesa das plantas contra a herbivoria e a redução do seu número nas folhas tornaria as plantas estressadas mais suscetíveis ao ataque de larvas de mariposas, fato corroborado por uma maior sobrevivência larval. Uma das possíveis explicações para a falta de corroboração da hipótese de estresse de planta para a maioria das variáveis testadas é que outras características podem ser alteradas sob condições de estresse, como a concentração de compostos secundários.(AU)

Effect of light stress on Crotalaria spectabilis (Fabaceae) and on its herbivore insect, the moth Utetheisa ornatrix (Erebidae: Arctiinae) / Efeito do estresse luminoso sobre Crotalaria spectabilis (Fabaceae) e seu inseto herbívoro, a mariposa Utetheisa ornatrix (Erebidae: Arctiinae)

The Plant Stress Hypothesis predicts that stressed plants are more attacked by herbivorous insects. In this work, we investigated the influence of light stress on Crotalaria spectabilis Roth (Fabaceae) and on its main herbivore, the moth Utetheisa ornatrix (L., 1758) (Erebidae: Arctiinae). Specifically, we verified whether plants stressed by shading differ from non-stressed plants in terms of productivity, morphological characteristics and water percentage. We also evaluated the performance of moths in stressed and non-stressed plants. Seeds were sown in pots. When the plants reached 50 cm in height, they were randomly divided into two groups: stressed plants (treatment group) and non-stressed plants (control group). The stressed plants were covered by a black mesh, providing 50% of shading. Eight characteristics of stressed and non-stressed C. spectabilis plants were evaluated: height, fresh and dry aerial biomass, number of pods and seeds, leaf hardness, number of trichomes, leaf area, specific leaf mass and percentage of leaf water. Moths were raised individually on leaves of stressed and non-stressed plants and we obtained the larval survival, larval development time, pupal weight and female fecundity. The non-stressed plants had significantly higher percentage of water in the leaves, greater fresh aerial biomass and a higher number of trichomes than the stressed plants. The survival rate was 98% for larvae raised on leaves from stressed plants and 92% on leaves from non-stressed plants. The larval developmental time was significantly shorter and the weight of female pupae significantly higher in non-stressed plants than in stressed plants. Thus, the Plant Stress Hypothesis was only corroborated by two tested variables: number of trichomes (lower in stressed plants) and larval survival (higher in stressed plants). Trichomes are among the main types of plant defenses against herbivory and reducing their number on leaves would make stressed plants more susceptible to attack by moth larvae, a fact corroborated by a greater larval survival. One of the possible explanations for the lack of corroboration of the Plant Stress Hypothesis for most of the variables tested is that other characteristics can be changed under stress conditions, such as the concentration of secondary compounds.

Efeito do estresse luminoso sobre Crotalaria spectabilis (Fabaceae) e seu inseto herbívoro, a mariposa Utetheisa ornatrix (Erebidae:Arctiinae) A hipótese do estresse da planta prevê que as plantas estressadas são mais atacadas por insetos herbívoros. Neste trabalho, investigamos a influência do estresse luminoso em Crotalaria spectabilis Roth (Fabaceae) e em seu principal herbívoro, a mariposa Utetheisa ornatrix (L., 1758) (Erebidae: Arctiinae). Especificamente, verificamos se as plantas estressadas por sombreamento diferem das plantas não estressadas em termos de produtividade, características morfológicas e porcentagem de água. Também avaliamos o desempenho das mariposas em plantas estressadas e não estressadas. As sementes foram semeadas em vasos. Quando as plantas atingiram 50 cm de altura, foram divididas aleatoriamente em dois grupos: plantas estressadas (grupo de tratamento) e plantas sem estresse (grupo controle). As plantas estressadas foram cobertas por uma malha preta, proporcionando 50% de sombreamento. Foram avaliadas oito características de plantas estressadas e não estressadas de C. spectabilis: altura, biomassa aérea fresca e seca, número de vagens e sementes, dureza foliar, número de tricomas, área foliar, massa foliar específica e porcentagem de água foliar. As mariposas foram criadas individualmente em folhas de plantas estressadas e não estressadas. Obtivemos a sobrevivência larval, o tempo de desenvolvimento larval, o peso pupal e a fecundidade das fêmeas. As plantas não estressadas apresentaram porcentagem significativamente maior de água nas folhas, maior biomassa aérea fresca e um maior número de tricomas do que as plantas estressadas. A taxa de sobrevivência foi de 98% para larvas criadas em folhas de plantas sob estresse e 92% em folhas de plantas sem estresse. O tempo de desenvolvimento larval foi significativamente menor e o peso das pupas femininas significativamente maior em plantas sem estresse do que em plantas estressadas. Assim, a hipótese de estresse em plantas foi corroborada apenas por duas variáveis testadas: número de tricomas (menor nas plantas estressadas) e sobrevivência larval (maior nas plantas estressadas). Os tricomas estão entre os principais tipos de defesa das plantas contra a herbivoria e a redução do seu número nas folhas tornaria as plantas estressadas mais suscetíveis ao ataque de larvas de mariposas, fato corroborado por uma maior sobrevivência larval. Uma das possíveis explicações para a falta de corroboração da hipótese de estresse de planta para a maioria das variáveis testadas é que outras características podem ser alteradas sob condições de estresse, como a concentração de compostos secundários.