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Seasonal soil freezing (F) and freeze–thaw cycles (FTCs) are common natural phenomena in high latitude or altitude areas of the world, and seriously affect plant physiological processes. However, studies on the effect of soil F and FTCs on fine roots are less common, especially in subalpine coniferous forests of western Sichuan, China.We set up a controlled experiment in growth chambers to explore the effects of F and FTCs on low‐order fine roots of Picea asperata and differential responses of first‐order roots and the first three root orders (1st, 2nd and 3rd order roots combined as a unit).Soil F and FTCs resulted in serious damage to cell membranes and root vitality of low‐order fine roots, accompanied by increased MDA content and O2·− production. FTCs had a stronger effect than F treatment. In turn, low‐order fine roots are the unit that responds to cold stress. These roots had increased unsaturated fatty acid contents, antioxidant enzyme activities, osmolytes and plant hormones contents when acclimation to cold stress. The first‐order roots were more sensitive to cold stress than the combined first three root orders for several processes (e.g. antioxidant enzymes, osmolytes and hormones) because of their specific structure and physiological activity.This study explains physiological differences in responses of fine roots of different root orders to seasonal soil freezing, which will improve the understanding of fine root heterogeneity and support agriculture and forest management. [ABSTRACT FROM AUTHOR]

Nickel (Ni) excess often generates oxidative stress in chloroplasts, causing redox imbalance, membrane damage and negative impacts on biomass. 24‐Epibrassinolide (EBR) is a plant growth regulator of great interest to the scientific community because it is a natural molecule extracted from plants, is biodegradable and environmentally friendly. This study aimed to determine whether EBR can improve ionic homeostasis, antioxidant enzymes, PSII efficiency and biomass by evaluating nutritional, physiological, biochemical and morphological responses of soybean plants subjected to Ni excess.The experiment used four randomized treatments, with two Ni concentrations (0 and 200 μm Ni, described as –Ni2+ and +Ni2+, respectively) and two concentrations of EBR (0 and 100 nm EBR, described as –EBR and +EBR, respectively).In general, Ni had deleterious effects on chlorophyll fluorescence and gas exchange. In contrast, EBR enhanced the effective quantum yield of PSII photochemistry (15%) and electron transport rate (19%) due to upregulation of SOD, CAT, APX and POX.Exogenous EBR application promoted significant increases in biomass, and these results were explained by improved nutrient content and ionic homeostasis, as demonstrated by increased Ca2+/Ni2+, Mg2+/Ni+2 and Mn2+/Ni2+ ratios. [ABSTRACT FROM AUTHOR]

The cytokinin two‐component signal transduction system (TCS) is involved in many biological processes, including hormone signal transduction and plant growth regulation. Although cytokinin TCS has been well characterized in Arabidopsis thaliana, its role in tomato remains elusive.In this study, we characterized the diversity and function of response regulator (RR) genes, a critical component of TCS, in tomato. In total, we identified 31 RR genes in the tomato genome. These SlRR genes were classified into three subgroups (type‐A, type‐B and type‐C).Various stress‐responsive cis‐elements were present in the tomato RR gene promoters. Their expression responses under pesticide treatment were evaluated by transcriptome analysis. Their expression under heat, cold, ABA, salinity and NaHCO3 treatments was further investigated by qRT‐PCR and complemented with the available transcription data under these treatments. Specifically, SlRR13 expression was significantly upregulated under salinity, drought, cold and pesticide stress and was downregulated under ABA treatment. SlRR23 expression was induced under salt treatment, while the transcription level of SlRR1 was increased under cold and decreased under salt stress.We also found that GATA transcription factors played a significant role in the regulation of SlRR genes. Based on our results, tomato SlRR genes are involved in responses to abiotic stress in tomato and could be implemented in molecular breeding approaches to increase resistance of tomato to environmental stresses. [ABSTRACT FROM AUTHOR]

Members of the GAPDH family play important roles in plant growth and development, as well as in stress responses. Our aim was to identify stress resistance genes through systematic analysis of the GAPDH family in watermelon. This could not only provide genetic resources for stress resistance breeding, but also form a basis for the study of plant stress resistance mechanisms.Eight GAPDHs representing four types of plant GAPDH in watermelon were identified (ClGAPA/B, ClGAPC1‐3, ClGAPCp1‐2 and ClGAPN). A comprehensive analysis of physicochemical properties, chromosome distribution, evolutionary relationships, exon‐intron structure and conserved motifs of watermelon GAPDHs was performed using bioinformatics. Expression characteristics were assessed by RT‐qPCR. Based on RT‐qPCR results, ClGAPC2 was screened as a candidate for subcellular localization analysis and functional verification in Arabidopsis thaliana.Eight GAPDHs were classified into four subfamilies. GAPDHs in each subgroup were generally conserved and shared similarities in structure and conserved motifs. ClGAPDHs had notable tissue specificity and different expression patterns in response to H2O2, chilling, salt, osmotic stress, heat, salicylic acid, gibberellin, brassinosterol, ethylene and abscisic acid treatments. Three ClGAPC genes, especially ClGAPC2, were markedly induced by several treatments. ClGAPC2 was located in the nucleus and cytoplasm of tabacum epidermal cells. The ClGAPC2 transgenic Arabidopsis showed enhanced tolerance to salinity at the germination stage.We suggest that ClGAPC2 plays important roles in the adaptation of watermelon to salinity. Our findings provided candidate genes for further improving the salt tolerance of watermelon. [ABSTRACT FROM AUTHOR]

Carbamoyl phosphate synthetase (CPS) catalyses the synthesis of ammonia carbamoyl phosphate (CP), which plays a key role in the biosynthesis of arginine and pyrimidine nucleotides. There are two subunits of the CPS enzyme in Populus trichocarpa, CarA (small subunit) and CarB (large subunit). Only when they coexist can CPS catalyse synthesis of CP. However, it is not clear how CPS responds to nitrogen (N) to affect arginine and pyrimidine nucleotide biosynthesis.In this study, bioinformatics methods were used to analyse the expression patterns of genes encoding CarA and CarB, and qRT‐PCR and RNA‐seq were used to investigate their molecular responses under different N concentrations.Phylogenetic analysis revealed that the phylogenetic trees of CarA and CarB had similar topologies. qRT‐PCR showed that the PtCarA and PtCarB genes were regulated by N, while their N‐regulated patterns differed in different tissues. The expression patterns of PtCarA and PtCarB show a significant positive correlation according to qRT‐PCR and RNA‐seq. The analysis of promoter cis‐acting elements showed that the promoter regions of PtCarA1, PtCarA2 and PtCarB contained some identical cis‐acting elements. According to analysis of the phylogenetic tree, expression patterns and promoter elements, we speculate that there might be coevolution among PtCarA1, PtCarA2 and PtCarB.This study provides valuable information for further understanding the function of CPS in poplar, especially for N response, and provides new ideas for studying the evolution of gene families related to heteromultimers. [ABSTRACT FROM AUTHOR]

Lilium pumilum is an excellent wildflower germplasm resource with high resistance to salinity stress. The gene LpBCP plays an important role in salinity tolerance of L. pumilum. Studying the molecular mechanism of salinity resistance in L. pumilum will provide insights into multiple aspects, including breeding better varieties, environmental protection, improving soil conditions, etc.Conventional methods were used to determine different physiological indicators of Nicotiana benthamiana after NaHCO3 treatment, i.e. chlorophyll content, soluble phenol content and lignin content. RT‐qPCR was carried out to find expression of LpBCP in different organs and under abiotic stresses. DAB was used to detect H2O2 in leaves in situ. A yeast two‐hybrid system was used to screen for LpBCP interacting proteins.LpBCP was cloned from bulbs of L. pumilum. The highest expression of LpBCP was in roots and bulbs of transgenic plants. LpBCP‐overexpressed plants showed less wilting, compared to WT plants. LpBCP transgenic plants have higher chlorophyll, soluble phenol and lignin content, and lower relative conductivity under 500 mM NaHCO3 stress. In addition, H2O2 scavenging in transgenic plants was much improved, indicating increased resistance to NaHCO3 stress. Thirteen LpBCP‐interacting proteins were screened using the yeast two‐hybrid method and five were associated with salt stress.Based on our findings, LPBCP could be a key gene that can be used to improve L. pumilum salt tolerance. [ABSTRACT FROM AUTHOR]

The plant IQD gene family is responsive to a variety of stresses. In this study, we studied the structural features and functions of the gene BrIQD35 in Chinese cabbage, a member of the IQD gene family.BrIQD35 was cloned and shown to contain an IQ motif. Transient expression of BrIQD35 indicated that it was localized on the plasma membrane and was significantly upregulated under drought and salt stress in Chinese cabbage. To further identify the function of BrIQD35, it was heterologously overexpressed in Nicotiana benthamiana. Although there was no significant difference between BrIQD35‐overexpressed and wild‐type (WT) plants under salt stress, WT N. benthamiana showed more wilting than the BrIQD35‐overexpressed plants under drought stress.Since the IQ motif has been annotated as a CaM binding site, yeast two‐hybrid assays were used to explore the interaction between BrIQD35 and CaM. The results indicated that BrIQD35 interacts weakly with CaMb, but not with CaMa, suggesting that BrIQD35 may function through the Ca2+‐CaMb pathway.The findings reveal a novel gene involved in drought tolerance, which is important for plant breeding and quality improvement for Chinese cabbage. [ABSTRACT FROM AUTHOR]

Slag produced in mining and smelting of manganese carbonate ore potentially pollutes the environment and endangers the health of humans and other living organisms.This study investigates the uptake of six heavy metals, Cu, Pb, Mn, Zn, Cr and Cd, by bryophytes and vascular plants growing on manganese carbonate slag in the Houshangou Slag Field near Zunyi City, Guizhou Province, China. Determination of heavy metal uptake in bryophytes and vascular plants may identify species suitable as biomonitors for bioremediation of polluted lands.Eight bryophyte taxa were identified in the study area; among which, Bryum argenteum and Physcomitrium eurystomum were dominant; life forms of bryophytes were predominantly short turfs. Three monocotyledons, all Poaceae, and five dicotyledons were recorded in four families. The highest heavy metal uptake in bryophytes, Mn content by B. argenteum, was more than 25,000 mg·kg−1. Furthermore, determination of heavy metal content in roots, leaves and fruits of six vascular plants demonstrated that each had a unique capacity for heavy metal accumulation: roots, leaves and fruits of similar plant species exhibited varying uptake capacity. Mn content in leaves was recorded in the order: B. davidii > A. tricolor > E. crus‐galli > C. argentea > P. acinosa > C. album.In summary, B. argenteum, Echinochloa crus‐galli and Phytolacca acinosa have strong enrichment capacity for heavy metals. These species could be used for comprehensive treatment of heavy metal pollution in electrolytic Mn slag fields, and for bioremediation of polluted areas associated with Mn mining and processing. [ABSTRACT FROM AUTHOR]

Iron (Fe) is an essential element for plant growth and development. Fe deficiency can trigger leaf chlorosis and reduce fruit yield. Therefore, it is necessary to explore transcription factors in response to Fe deficiency stress.A total of 29 MhR2R3‐MYB transcription factors were identified based on the transcriptome of Malus halliana under Fe deficiency stress. A comprehensive analysis of physical and chemical properties, gene structures, conserved motif composition, evolutionary relationship and chromosome distribution was performed. Subsequently, based on the transcriptome, 14 genes with the most significant expression under Fe deficiency stress were screened for qRT‐PCR verification. Among them,the functional characteristics of MhR2R3‐MYB4 (MD05G1089600) were further studied in Arabidopsis thaliana.Expression of 13 out of these 14 genes was upregulated, only one was downregulated. Maximum upregulation of MhR2R3‐MYB4 under Fe deficiency was 36.39‐fold and 58.21‐fold compared with day 0 in leaves and roots, respectively. Overexpression of MhR2R3‐MYB4 enhanced tolerance to Fe deficiency in A. thaliana and led to multiple biochemical changes: transgenic lines have higher chl a, chl b and Fe2+ content, higher enzyme activity (SOD, POD, CAT and FCR) and lower chlorosis than the wild type in Fe deficiency conditions.We suggest that MhR2R3‐MYB4 plays an important part in Fe deficiency stress, which may contribute to improve Fe deficiency tolerance of apple in future. [ABSTRACT FROM AUTHOR]

Symbiotic nitrogen fixation in legumes is an important source of nitrogen supply in sustainable agriculture. Salinity is a key abiotic stress that negatively affects host plant growth, rhizobium–legume symbiosis and nitrogen fixation. This work investigates how the symbiotic relationship impacts plant response to salinity stress.We assayed the physiological changes and the proteome profile of alfalfa plants with active nodules (NA), inactive nodules (NI) or without nodules (NN) when plants were subjected to salinity stress.Our data suggest that NA plants respond to salinity stress through some unique signalling regulations. NA plants showed upregulation of proteins related to cell wall remodelling and reactive oxygen species scavenging, and downregulation of proteins involved in protein synthesis and degradation. The data also show that NA plants, together with NI plants, upregulated proteins involved in photosynthesis, carbon fixation and respiration, anion transport and plant defence against pathogens.The study suggests that the symbiotic relationship gave the host plant a better capacity to adjust key processes, probably to more efficiently use energy and resources, deal with oxidative stress, and maintain ion homeostasis and health during salinity stress. [ABSTRACT FROM AUTHOR]

Climate change is increasing the frequency of high temperature shocks and water shortages, pointing to the need to develop novel tolerant varieties and to understand the mechanisms employed to withstand combined abiotic stresses.Two tomato genotypes, a heat‐tolerant Solanum lycopersicum accession (LA3120) and a novel genotype (E42), previously selected as a stable yielding genotype under high temperatures, were exposed to single and combined water and heat stress. Plant functional traits, pollen viability and physiological (leaf gas exchange and chlorophyll a fluorescence emission measurements) and biochemical (antioxidant content and antioxidant enzyme activity) measurements were carried out. A Reduced Representation Sequencing approach allowed exploration of the genetic variability of both genotypes to identify candidate genes that could regulate stress responses.Both abiotic stresses had a severe impact on plant growth parameters and on the reproductive phase of development. Growth parameters and leaf gas exchange measurements revealed that the two genotypes used different physiological strategies to overcome individual and combined stresses, with E42 having a more efficient capacity to utilize the limiting water resources. Activation of antioxidant defence mechanisms seemed to be critical for both genotypes to counteract combined abiotic stresses. Candidate genes were identified that could explain the different physiological responses to stress observed in E42 compared with LA3120.Results here obtained have shown how new tomato genetic resources can be a valuable source of traits for adaptation to combined abiotic stresses and should be used in breeding programmes to improve stress tolerance in commercial varieties. [ABSTRACT FROM AUTHOR]

Many saline‐alkali soils around the world are polluted by the heavy metal Cd, restricting the development of agriculture and ecology in those regions. The halophyte Salicornia europaea L. is capable of growing healthily in Cd‐contaminated saline‐alkali soil, suggesting that the species is tolerant to stress caused by both salt and heavy metals. In this study, the mechanism of Cd tolerance in this species was explored under 200 mM NaCl.Flame spectrophotometric assays for ions content and spectrophotometric for organic soluble substances, antioxidant enzyme activity, phytochelatins (PCs) content and phytochelatin synthase (PCS) activity, the photosynthetic parameters by portable photosynthesis measurement system, genes expression by qRT‐PCR analysis were carried out.Cd treatment significantly decreased the dry weight, photosynthetic rate, K+, Zn2+, and Fe2+/3+ content, while significantly increasing Na+ and Cd+, soluble organic matter, and reactive oxygen species (ROS) levels. Compared with Cd treatment at 0 mM NaCl, Cd treatment at 200 mM NaCl significantly increased dry weight and photosynthetic rate while significantly decreasing ROS content through increased antioxidant enzyme activity. When exposed to Cd stress, treatment with 200 mM NaCl significantly increased PCs content and PCS activity and up‐regulated the expression of the phytochelatin synthase genes CDA1 and PCS1 were, thereby increasing resistance to Cd.NaCl treatment increases the tolerance of S. europaea to the heavy metal Cd by growing rapidly, reducing the quantity of Cd2+ from entering the plant shoots, increasing the levels of PCs that chelate Cd2+, thereby reducing its toxicity. [ABSTRACT FROM AUTHOR]

Plant growth and productivity is restricted by a multitude of abiotic stresses. These stresses negatively affect physiological and metabolic pathways, leading to the production of many harmful substances like ROS, lipid peroxides and aldehydes. This study was conducted to investigate the role of Arabidopsis ALDH3I1 gene in multiple abiotic stress tolerance.Transgenic tobacco plants were generated that overexpress the ALDH3I1 gene driven by the CaMV35S promoter and evaluated under different abiotic stresses, namely salt, drought, cold and oxidative stress. Tolerance to stress was evaluated based on responses of various growth and physiological traits under stress condition.Transgenic plants displayed elevated ALDH3I1 transcript levels compared to WT plants. The constitutive ectopic expression of ALDH3I1 conferred increased tolerance to salt, drought, cold and oxidative stresses in transgenic plants, along with improved plant growth. Transgenic plants overexpressing ALDH3I1 had higher chlorophyll content, photosynthesis rate and proline, and less accumulation of ROS and malondialdehyde compared to the WT, which contributed to stress tolerance in transgenic plants. Our results further revealed that ALDH3I1 had a positive effect on CO2 assimilation rate in plants under abiotic stress conditions.Overall, this study revealed that ALDH3I1 positively regulates abiotic stress tolerance in plants, and has future implications in producing transgenic cereal and horticultural plants tolerant to abiotic stresses. [ABSTRACT FROM AUTHOR]

Universal stress proteins (USPs) are a conserved group of proteins initially identified and characterized in bacteria. USPs are induced under multiple stresses, and are important for stress acclimation. We cloned a USP‐like gene designated as MaUSP1‐like from mulberry and expressed in bacteria and tobacco to examine its relevance in abiotic stress tolerance.Escherichia coli and tobacco cells expressing MaUSP1‐like gene were exposed to different abiotic stresses, and cell survival and growth was recorded to assess the stress effects.MaUSP1‐like gene conferred tolerance to E. coli cells under NaCl‐induced salt stress, PEG8000‐induced desiccation stress, cadmium chloride‐induced heavy metal stress, and heat stress. Overexpression of MaUSP1‐like sustained cell division and growth in tobacco cells under salt stress.The results demonstrate that MaUSP1‐like gene is capable of conferring cellular level tolerance in both prokaryotic and eukaryotic systems, under abiotic stress. The finding opened up an option to argue that maintenance of cellular level tolerance is crucial for sustenance of growth under stress and cellular level tolerance can be improved by overexpressing genes like USPs. [ABSTRACT FROM AUTHOR]

Pecan (Carya illinoinensis) is sensitive to Zn, which is involved in basic physiological and biochemical processes.To explore the growth and physiology of pecan in response to Zn application, we used 1‐year‐old annual grafted seedlings (Pawnee) and applied four concentrations of Zn fertilizer (0.05, 0.10, 0.20 and 0.40 g·plant−1); a control (CK; no Zn fertilization) was also included. The growth characteristics, anatomical structure of the leaves and photosynthesis were assessed.Compared with the CK, photosynthesis and chlorophyll (Chl) fluorescence parameters, leaf area and leaf structure significantly increased at Zn concentrations of 0.05 and 0.10 g·plant−1. In addition, growth of pecan at the seedling stage increased in response to moderate Zn application. In contrast, treatment with 0.20 and 0.40 g·Zn·plant−1 dramatically decreased these physiological indices and inhibited pecan growth.The results show that moderate soil Zn application promotes pecan growth and development by increasing photosynthesis. However excess Zn concentrations were not conducive to seedling growth. The concentration of 0.1 g·Zn·plant−1 was best when considering long‐term soil Zn applications, providing a theoretical foundation for microelement management of pecan. [ABSTRACT FROM AUTHOR]

Although copper is essential for plant growth and development and plays an important role in many physiological processes, excess copper, resulting from industrial development and population expansion in the recent decades, leads to environmental pollution and has been a cause of wide concern for the adverse effects on photosynthesis, metabolism and growth of plants.The growth properties (e.g. fresh weight, root length, height), photosynthetic properties (e.g. gas exchange, chlorophyll a fluorescence, chlorophyll content) and the physiological index (e.g. activity of antioxidant enzymes and osmotic regulators) of Eichhornia crassipes were assessed under various Cu2+ concentrations in hydroponic experiments.The growth of E. crassipes was negatively affected by Cu2+ treatments, especially at higher Cu2+ concentrations; the Cu2+ treatments resulted in decreased photosynthesis because of a decrease in leaf chlorophyll content and damage to PSII functions, except the oxygen‐evolving complex. The physiological tolerance of E. crassipes to Cu2+ relies on osmotic regulation, anti‐lipid peroxidation and improved antioxidant properties.The results indicate that E. crassipes could be considered as a phytoremediation agent for Cu2+ pollution in aquatic environments. However, the benefit of E. crassipes for Cu2+ removal in a highly polluted aquatic environment will be limited, but it will be effective in remediating sites with low pollution (≤5 mg·l−1). The present results could provide not only a basis for understanding the effects of pollutants on photosynthesis in plants under heavy metal stress but also provide a basis for choosing plants for phytoremediation. [ABSTRACT FROM AUTHOR]

Salt is among the most harmful agents that negatively influences crop yield. Alfalfa is an important perennial forage crop that exhibits wide cultivar variations in salt tolerance. Developing salt‐tolerant alfalfa plants is a promising way to utilize salinized land.A comprehensive method was developed to achieve reliable and effective evaluation of alfalfa salt resistance. This included principal components, membership functions and cluster and stepwise regression analyses. These were used to analyse the salt tolerance coefficients of 14 traits and to evaluate 20 diverse alfalfa cultivars at the seedling stage. The various morphological root parameters of six alfalfa cultivars with contrasting salt tolerance were also tested by a scanning apparatus.According to the comprehensive evaluation value (D value), one highly salt‐tolerant, two salt‐tolerant, four moderately salt‐tolerant and 13 salt‐sensitive alfalfa cultivars were screened. A mathematical equation for the evaluation of alfalfa salt tolerance was established: D′ = −0.126 + 0.667SFW + 0.377SDW + 1.089K+/Na+ + 0.172SFW/RFW (R2 = 0.988; average forecast accuracy of 96.95%), where four indices were closely related to the salt tolerance: shoot fresh weight, ratio of shoot fresh weight to root fresh weight, shoot dry weight and ratio of K+ to Na+ in the shoot. We also found that SSA correlated strongly with SFW, SDW, K+/Na+, D values, while SRV correlated obviously with SFW, SFW/RFW and D values after 150 mm NaCl treatment.In conclusion, the SFW, K+/Na+, SDW, SFW/RFW, SSA and SRV could be used as indicators of salt tolerance in alfalfa seedlings grown under 150 mm NaCl treatment. [ABSTRACT FROM AUTHOR]

Drought is the most devastating stress for crops. Intensity and duration of drought determine the magnitude of plant damage; similarly, plant ability to counteract drought determines its tolerance capacity. Recent studies revealed that exogenous apocarotenoid treatment confers abiotic stress tolerance to plants. However, much less is known about the role of β‐cyclocitral (βCC), the major apocarotenoid, in drought tolerance. Here, we demonstrate βCC's role in improving plants' tolerance against drought stress.Tomato (Solanum lycopersicum L.) plants were independently treated with water and βCC and grown under either water‐limited or irrigated conditions. The βCC‐treated drought‐exposed (BD) and βCC‐treated irrigated (BH) plants were analysed for the major drought tolerance associated traits; water‐treated drought‐exposed (CD) and water‐treated irrigated plants (CH) were used as controls.On exposure to drought, unlike controls, βCC‐treated plants showed no wilting, higher RWC and stomatal conductance, unchanged ABA levels and stomatal closure. The BD plants had increased photosynthesis, chlorophyll content and enhanced root, but not shoot, growth. In addition, βCC treatment enhanced proline accumulation and activity of SOD in both drought‐exposed and well irrigated plants.Taken together, βCC was identified as a potential candidate that improves tomato osmolyte accumulation and superoxide elimination, independent of ABA, and prepares the plant for upcoming drought stress. Our results suggest that βCC can be used to prime crops against drought stress. [ABSTRACT FROM AUTHOR]

Tall fescue (Festuca arundinacea) is an important grass species worldwide, but temperature stress severely affects its distribution and yield. Transcription factors (TFs), as the master switches in sophisticated regulatory networks, play essential roles in plant growth development and abiotic stress responses.In this study, the comparative transcriptome analysis was performed to explore the commonalities and differences in the response of TFs to the heat (40 °C), cold (10 °C) and control (22 °C) conditions.A total of 877 TF genes belonging to 35 families were identified. Most of them (784) were differentially expressed genes (DEG), indicating TF genes actively responded to temperature stress. The expression of bZIP and GTF family members was up‐regulated when exposed to both heat and cold, but conversely, the expression of the most WRKY and NAC families members decreased. The HSF and GTE families and DREB2B were up‐regulated upon heat, while bHLH, MYB, HD‐ZIP and ERF families were elevated under cold stress. The TFs involved in 'Plant hormone signal transduction', 'Plant‐pathogen interaction', 'Circadian rhythm' play major roles in responding to temperature stresses.The results showed the temperature threats up‐regulated the expression of stress tolerance‐related genes, and down‐regulated those genes associated with growth and disease resistance, indicating TFs exert crucial roles in plant adaptation to an adverse environment. This study profiled the responsive pattern of TFs to temperature stresses, partially explained the mechanism of adaptations of cold‐season forage crops and screened many candidate stress‐tolerant TF genes. [ABSTRACT FROM AUTHOR]

Phytochelatins (PCs) constitute an important mechanism for plants to resist heavy metal stress. Widely found in higher plants, they are small heavy metal binding peptides, synthesized through catalysis of phytochelatin synthase (PCS). We speculate that there may be PCS genes in Peacock grass (Tagetes patula L., Asteraceae), which is an important reason for its rich cadmium.In order to obtain the full‐length cDNA sequence of the PCS gene from T. patula L. used rapid amplification of cDNA ends (RACE). Meanwhile, Relative expression of TpPCS1 under different concentrations of cadmium (Cd) stress was analysed using quantitative real‐time polymerase chain reaction (qRT‐PCR).Results found ORF of TpPCS1 genes with a length of 1970 bp, a gene coding area length of 1764 bp, coding for 587 amino acids. Expression of TpPCS1 under Cd stress was tissue specific. TpPCS1 in the root showed higher expression, while expression in the leaf and seed was relatively low.This research demonstrates that expression of TpPCS1 enhanced the enrichment of cadmium in T. patula L. roots and could be used to construct a plant hyperexpression carrier that would provide new avenues for plant restoration technology. [ABSTRACT FROM AUTHOR]

Inducer of CBF expression 1 (ICE1), a MYC‐like bHLH transcriptional activator, plays an important role in plants under cold stress. The ubiquitination–proteasome pathway mediated by high expression of osmotically responsive gene1 (HOS1) can effectively induce the degradation of ICE1 and decrease the expression of CBFs and their downstream genes under cold stress response in Arabidopsis, but knowledge of ubiquitination regulation of ICE1 by HOS1 is still limited in woody plants.In this study, a E3 ubiquitin ligase gene EcaHOS1 were amplified from Eucalyptus camaldulensis and the protein interactions between EcaICE1 and EcaHOS1 were analysed.Yeast two‐hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assay results showed that EcaICE1 can interact with the EcaHOS1 protein in the nucleus and, further, the Y2H assay demonstrated that the 126–185 amino acid region at the N‐terminus of the EcaICE1 protein was indispensable for its interaction with EcaHOS1 protein. Moreover, we found that the amino acids at positions 145, 158 and 184 within the key interaction region were the putative phosphorylation sites of EcaICE1, based on bioinformatics analysis, and only the substitution of serine (Ser) 158 by alanine (Ala) blocked the protein–protein interactions between EcaICE1 and EcaHOS1 based on Y2H and β‐galactosidase activity assays using site‐directed mutagenesis.We identified Ser 158 of EcaICE1 as the key putative phosphorylation site for its interaction with the EcaHOS1 protein. [ABSTRACT FROM AUTHOR]

Polyamines play an important role in stress response. In the pathway of polyamines synthesis, S-adenosylmethionine decarboxylase (SAMDC) is one of the key enzymes. In this study, a full length cDNA of SAMDC (AhSAMDC) was isolated from peanut (Arachis hypogaea L.). Phylogenetic analysis revealed high sequence similarity between AhSAMDC and SAMDC from other plants.In peanut seedlings exposed to sodium chloride (NaCl), the transcript level of AhSAMDC in roots was the highest at 24 h that decreased sharply at 72 and 96 h after 150 mM NaCl treatment. However, the expression of AhSAMDC in peanut leaves was significantly inhibited, and the transcript levels in leaves were not different compared with controlThese results implied the tissue‐specific and time-specific expression of AhSAMDC. The physiological effects and functional mechanism of AhSAMDC were further evaluated by overexpressing AhSAMDC in tobaccos. The transgenic tobacco lines exhibited higher germination rate and longer root length under salt stress. Reduced membrane damage, higher antioxidant enzyme activity, and higher proline content were also observed in the transgenic tobacco seedlings. What's more, AhSAMDC also led to higher contents of spermidine and spermine, which can help to scavenge reactive oxygen species.Together, this study suggests that AhSAMDC enhances plant resistance to salt stress by improving polyamine content and alleviating membrane damage [ABSTRACT FROM AUTHOR]

Copper‐tolerant (Cu) plants with high ornamental value play an important role in the ecological restoration of the copper tail mining area. We first discovered Celosia argentea adaptability in a copper mine area in China; however, its resistance to Cu and the underlying mechanism are not clear.In this study, C. argentea was selected for pot culture experiments. Its heavy metal accumulation and translocation, physiological and metabolic products were analysed under different growth concentrations of Cu (0–2400 mg.kg−1) stress.Our results indicated that roots strongly accumulated Cu2+. Oxidative stress defence mechanisms were activated in leaves under Cu treatment. Higher Cu concentrations triggered higher electrolyte leakage (EL), Malondialdehyde (MDA), superoxide dismutase (SOD) and peroxidase (POD) activity, and consequently a higher capacity to scavenge oxygen radicals and maintain cellular membrane integrity. In the citrate cycle, some amino acids and sugars related to biological pathways were altered in C. argentea exposed to Cu stress. Metabolomics data revealed that C. argentea used elevated sugar content as an antioxidant to regulate reactive oxygen species (ROS). Some organic acids and amino acids were up‐regulated compared with the control, indicating that these may chelate Cu in cells to remove excess Cu2+. The up‐regulation of polyamines and some organic acids may mitigate oxidative stress.These results indicate that C. argentea could be used as a Cu‐tolerant plant in Cu mine restoration. Its Cu tolerance mechanism also provides a basis for future plant improvement or breeding for use in mine restoration. [ABSTRACT FROM AUTHOR]

The Cadmium (Cd)‐polluted soils are is an increasing concern worldwide. Phytoextraction of Cd pollutants by high biomass plants, such as sweet sorghum, is considered an environmentally‐friendly, cost‐effective and sustainable strategy for remediating this problem. Nitrogen (N) is a macronutrient essential for plant growth, development and stress resistance. Nevertheless, how nitrate, as an important form of N, affects Cd uptake, translocation and accumulation in sweet sorghum is still unclear.In the present study, a series of nitrate levels (N1, 0.5 mm; N2, 2 mm; N3, 4 mm; N4, 8 mm and N5, 16 mm) with or without added 5 μm CdCl2 treatment in sweet sorghum was investigated hydroponically.The results indicate that Cd accumulation in the aboveground parts of sweet sorghum was enhanced by optimum nitrate supply, resulting from both increased dry weight and Cd concentration. Although root‐to‐shoot Cd translocation was not enhanced by increased nitrate, some Cd was transferred from cell walls to vacuoles in leaves. Intriguingly, expression levels of Cd uptake and transport genes, SbNramp1, SbNramp5 and SbHMA3, were not closely related to increased Cd as affected by nitrate supply. The expression of SbNRT1.1B in relation to nitrate transport showed an inverted 'U' shape with increasing nitrate levels under Cd stress, which was in agreement with trends in Cd concentration changes in aboveground tissues.Based on the aforementioned results, nitrate might regulate Cd uptake and accumulation through expression of SbNRT1.1B rather than SbNramp1, SbNramp5 or SbHMA3, the well‐documented genes related to Cd uptake and transport in sweet sorghum. [ABSTRACT FROM AUTHOR]

The soybean is a legume that is widely cultivated in many countries due to the high levels of protein and oil contained in its seed, and is used for human and animal nutrition. However, salinity affects more than 800 million hectares worldwide, limiting global agricultural production.The aim of this research was to evaluate the structural behaviour of the roots and stems under progressive salt stress, detailing the possible anatomical modifications to these organs in soybean plants during this stress. The plants were randomized into five treatments (0, 50, 100, 150 and 200 mm NaCl).All the root regions studied and exposed to 100 mm Na+ exhibited increases in the epidermis and endodermis and formation of lysogenic aerenchyma with increasing salinity, revealing the protective roles of these structures in reducing Na+ influx. In the stem, increases in the cortex and pith in the first internode subject to 100 mm Na+ suggest anatomical responses that aim to minimize oxidative stress.Soybean plants subjected to progressive salt stress (>50 mm Na+) avoided cavitation and loss of function linked to vessel elements, reducing the metaxylem in all the root and stem regions analysed. Finally, our results confirm anatomical changes to the roots and stems. [ABSTRACT FROM AUTHOR]

In the present study, a TINY‐like AP2/ERF gene, PvERF35i, was amplified from common bean (Phaseolus vulgaris L.), cloned and functionally characterized by overexpressing in tobacco cv. Petite havana.Transgenic plants overexpressing PvERF35 were generated using Agrobacterium‐mediated transformation and used to evaluate the possible roles of the transgene under salt stress conditions. Evaluation of transgenics was completed using both molecular and biochemical analysis.PCR, Southern blot and RT‐qPCR assays revealed the correct integration and enhanced expression of the transgene. Physiological and biochemical analysis of transgenic plants showed their better performance compared to the wild type in terms of germination and survival rates and root and shoot growth under salt stress treatment (200 mM NaCl). Having a high concentration of proline, APX and POX, the PvERF35 overexpressed plants were physiologically and morphologically less affected by salt stress application. In silico promoter analysis of the PvERF35 gene led to identification of important cis‐regulatory elements, MYB, MYC and TGACG‐motif, annotated with salt response of plants. The protein–protein interaction network showed that there was a strong association between ABC transporter proteins and PvERF35 protein. Salt stress‐related miRNA, miRNA156 and miRNA159, targeting PvERF35 were identified using in silico target finding analysis.These findings suggest that PvERF35 functions as a stress‐responsive transcription factor in differential modulation of salt stress tolerance and may have applications in the engineering of economically important crops. [ABSTRACT FROM AUTHOR]

Worldwide, 50% of soil is acidic, which induces aluminium (Al) toxicity in plants, as the phyto‐availability of Al3+ increases in acidic soil. Plants responds to Al3+ toxicity by exuding organic acids into the rhizosphere. The organic acid responsible for Al3+ stress response varies from species to species, which in the case of blackgram (Vigna mungo L.) is citrate.In blackgram, an Arabidopsis malate transporter, AtALMT1, was overexpressed with the motive of inducing enhanced exudation of malate. Transgenics were generated using cotyledon node explants through Agrobacterium tumefaciens‐mediated transformation. The putative transgenics were initially screened by AtALMT1‐specific genomic DNA PCR, followed by quantitative PCR. Two independent transgenic events were identified and functionally characterized in the T3 generation.The transgenic lines, Line 1 and 2, showed better root growth, relative water content and chlorophyll content under Al3+ stress. Both lines also accounted for less oxidative damage, due to reduced accumulation of ROS molecules. Photosynthetic efficiency, as measured in terms of Fv/Fm, NPQ and Y(II), increased when compared to the wild type (WT). Relative expression of genes (VmSTOP1, VmALS3, VmMATE) responsible for Al3+ stress response in blackgram showed that overexpression of a malate transporter did not have any effect on their expression. Malate exudation increased whereas citrate exudation did not show any divergence from the WT. A pot stress assay found that the transgenics showed better adaptation to acidic soil.This report demonstrates that the overexpression of a malate transporter in a non‐malate exuding species improves adaptation to Al3+ toxicity in acidic soil without effecting its stress response mechanism. [ABSTRACT FROM AUTHOR]

Aluminium (Al) toxicity is the major constraint for crop productivity in acid soils. Wild rye species (Secale spp.) exhibit high Al tolerance, being a good source of genes related to this trait. The Alt1 locus located on the 6RS chromosome arm is one of the four main loci controlling Al tolerance in rye and is known to harbour major genes but, so far, none have been found.Through synteny among the short arm of the rye chromosome 6R and the main grass species, we found a candidate MATE gene for the Atl1 locus, later named ScMATE3, which was isolated and characterized in different Secale species.The sequence comparisons revealed both intraspecific and interspecific variability, with high sequence conservation in the Secale genus. SNP with replacement substitution that changed the structure of the protein and can be involved in the Al tolerance trait were found in ScMATE3 gene. The predicted subcellular localization of ScMATE3 is the vacuolar membrane which, together with the phylogenetic relationships performed with other MATE genes of the Poaceae related to Al detoxification, suggest involvement of ScMATE3 in an internal tolerance mechanism. Moreover, expression studies of this gene in rye corroborate its contribution in some Al resistance mechanisms.The ScMATE3 gene is located on the 6RS chromosome arm between the same markers in which the Alt1 locus is involved in Al resistance mechanisms in rye, thus being a good candidate gene for this function. [ABSTRACT FROM AUTHOR]

Melatonin has emerged as an essential molecule in plants, due to its role in defence against metal toxicity. Aluminium (Al) and cadmium (Cd) toxicity inhibit rapeseed seedling growth.In this study, we applied different doses of melatonin (50 and 100 µm) to alleviate Al (25 µm) and Cd (25 µm) stress in rapeseed seedlings. Results show that Al and Cd caused toxicity in rapeseed seedling, as evidenced by a decrease in height, biomass and antioxidant enzyme activity.Melatonin increased the expression of melatonin biosynthesis‐related Brassica napus genes for caffeic acid O‐methyl transferase (BnCOMT) under Al and Cd stress. The genes BnCOMT‐1, BnCOMT‐5 and BnCOMT‐8 showed up‐regulated expression, while BnCOMT‐4 and BnCOMT‐6 were down‐regulated during incubation in water. Melatonin application increased the germination rate, shoot length, root length, fresh and dry weight of seedlings. Melatonin supplementation under Al and Cd stress increased superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, proline, chlorophyll and anthocyanin content, as well as photosynthesis rate. Both Cd and Al treatments significantly increased hydrogen peroxide and malondialdehyde levels in rapeseed seedlings, which were strictly counterbalanced by melatonin. Analysis of Cd and Al in different subcellular compartments showed that melatonin enhanced cell wall and soluble fractions, but reduced the vacuolar and organelle fractions in Al‐ and Cd‐treated seedlings.These results suggest that melatonin‐induced improvements in antioxidant potential, biomass, photosynthesis rate and successive Cd and Al sequestration play a pivotal role in plant tolerance to Al and Cd stress. This mechanism may have potential implications in safe food production. [ABSTRACT FROM AUTHOR]

Low temperature is a crucial environmental factor affecting the quality and production of eggplant. Therefore, it is necessary to explore the molecular mechanisms of low temperature response.We isolated an ICE (inducer of CBF expression) gene from Solanum melongena, named SmICE1a. We then analysed structure, transcriptional activity and expression patterns of SmICE1a. Moreover, we also expressed SmICE1a in Arabidopsis thaliana.Bioinformatics and expression analysis showed that SmICE1a has a typical S‐rich motif, ZIP region, bHLH and ACT‐like domain. The gene SmICE1a had transcriptional activity in yeast and was localized to the nucleus following transient expression in tobacco leaves, which suggests that SmICE1a is a transcription factor. A dual‐LUC assay revealed that SmICE1a can enhance expression of SmCBF. Overexpression of SmICE1a in Arabidopsis increased freezing tolerance and caused multiple biochemical changes: transgenic lines have higher proline content and lower electrolyte leakage and malondialdehyde than the wild type in cold conditions. The expression of AtCBF and their target genes, AtCOR15A, AtCOR47, AtKIN1 and AtRD29A, were up‐regulated in SmICE1a‐overexpressing plants under low temperatures.Based on these results, we suggest that SmICE1a plays an important role in cold response, which may help to understand the cold response mechanism in eggplant and could be used to enhance cold tolerance of eggplant in future. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is detrimental to crops and the environment. This work examines the natural mechanisms underlying silicon‐ (Si‐)directed Cd detoxification in rice plants.The addition of Si to plants under Cd stress caused significant improvements in morphological parameters, chlorophyll score, Fv/Fm and total soluble protein concentration compared to controls, confirming that Si is able to ameliorate Cd‐induced damage in rice plants. This morpho‐physiological evidence was correlated with decreased cell death and electrolyte leakage after Si application.The results showed no critical changes in root Cd concentration, while shoot Cd decreased significantly after Si supplementation in comparison with Cd‐stressed rice. Additionally, expression of Cd transporters (OsNRAMP5 and OsHMA2) was significantly down‐regulated while the concentration of phytochelatin, cysteine and glutathione, together with expression of OsPCS1 (phytochelatin synthase) in roots of Cd‐stressed rice was significantly induced when subjected to Si treatment. This confirms that the alleviation of Cd stress is not only limited to the down‐regulation of Cd transporters but also closely related to the phytochelatin‐driven vacuolar storage of Cd in rice roots.The enzymatic analysis further revealed the role of SOD and GR enzymes in protecting rice plants from Cd‐induced oxidative harm. These findings suggest a mechanistic basis in rice plants for Si‐mediated mitigation of Cd stress. [ABSTRACT FROM AUTHOR]

Nitrogen (N) could affect storage root growth and development of sweet potato. To manage external N concentration fluctuations, plants have developed a wide range of strategies, such as growth changes and gene expression.Five sweet potato cultivars were used to analyse the functions of N in regulating storage root growth. Growth responses and physiological indicators were measured to determine the physiological changes regulated by different N concentrations. Expression profiles of related genes were analysed via microarray hybridization data and qRT‐PCR analysis to reveal the molecular mechanisms of storage root growth regulated by different N concentrations.The growth responses and physiological indicators of the five cultivars were changed by N concentration. The root fresh weight of two of the sweet potato cultivars, SS19 and GS87, was higher under low N concentrations compared with the other cultivars. SS19 and GS87 were found to be having greater tolerance to low N concentration. The expression of N metabolism and storage root growth related genes was regulated by N concentration in sweet potato.These results reveal that N significantly regulated storage root growth. SS19 and GS87 were more tolerant to low N concentration and produced greater storage root yield (at 30 days). Furthermore, several N response genes were involved in both N metabolism and storage root growth. [ABSTRACT FROM AUTHOR]

We previously showed that Arabidopsis mda1 and mterf9 mutants, defective in the chloroplast‐targeted mitochondrial transcription termination factors mTERF5 and mTERF9, respectively, display altered responses to abiotic stresses and abscisic acid (ABA), as well as perturbed development, likely through abnormal chloroplast biogenesis.To advance the functional analysis of mTERF5 and mTERF9, we obtained and characterized overexpression (OE) lines. Additionally, we studied genetic interactions between sca3‐2, affected in the plastid‐RNA polymerase RpoTp, and the mda1‐1 and mterf9 mutations. We also investigated the role of mTERF5 and mTERF9 in plastid translation and plastid‐to‐nucleus signalling.We found that mTERF9 OE reduces salt and ABA tolerance, while mTERF5 or mTERF9 OE alter expression of nuclear and plastid genes. We determined that mda1‐1 and mterf9 mutations genetically interact with sca3‐2. Further, plastid 16S rRNA levels were reduced in mda1‐1 and mterf9 mutants, and mterf9 was more sensitive to chemical inhibitors of chloroplast translation. Expression of the photosynthesis gene LHCB1, a retrograde signalling marker, was differentially affected in mda1‐1 and/or mterf9 compared to wild‐type Col‐0, after treatments with inhibitors of carotenoid biosynthesis (norflurazon) or chloroplast translation (lincomycin). Moreover, mterf9, but not mda1‐1, synergistically interacts with gun1‐1, defective in GUN1, a central integrator of plastid retrograde signals.Our results show that mTERF9, and to a lesser extent mTERF5, are negative regulators of salt tolerance and that both genes are functionally related to RpoTp, and that mTERF9 is likely required for plastid ribosomal stability and/or assembly. Furthermore, our findings support a role for mTERF9 in retrograde signalling. [ABSTRACT FROM AUTHOR]

In polluted areas, plants may be exposed to supra‐optimal levels of the micronutrient molybdenum. The physiological basis of molybdenum phytotoxicity is poorly understood. Plants take up molybdenum as molybdate, which is a structural analogue of sulphate. Therefore, it is presumed that elevated molybdate concentrations may hamper the uptake and subsequent metabolism of sulphate, which may induce sulphur deficiency.In the current research, Chinese cabbage (Brassica pekinensis) seedlings were exposed to 50, 100, 150 and 200 μm Na2MoO4 for 9 days.Leaf chlorosis and a decreased plant growth occurred at concentrations ≥100 μm. Root growth was more affected than shoot growth. At ≥100 μm Na2MoO4, the sulphate uptake rate and capacity were increased, although only when expressed on a root fresh weight basis. When expressed on a whole plant fresh weight basis, which corrects for the impact of molybdate on the shoot‐to‐root ratio, the sulphate uptake rate and capacity remained unaffected. Molybdate concentrations ≥100 μm altered the mineral nutrient composition of plant tissues, although the levels of sulphur metabolites (sulphate, water‐soluble non‐protein thiols and total sulphur) were not altered. Moreover, the levels of nitrogen metabolites (nitrate, amino acids, proteins and total nitrogen), which are generally strongly affected by sulphate deprivation, were not affected. The root water‐soluble non‐protein thiol content was increased, and the tissue nitrate levels decreased, only at 200 μm Na2MoO4.Evidently, molybdenum toxicity in Chinese cabbage was not due to the direct interference of molybdate with the uptake and subsequent metabolism of sulphate. [ABSTRACT FROM AUTHOR]

Bauxite mining on karst generates numerous ecological and environmental problems, including metal pollution, water and soil erosion and destruction of vegetation. Among these, the most important environmental problem is soil metal pollution. Higher plants have a great ability to adsorb metals and can be used as biological indicators. However, the study of bioindicators for soil contamination in karst bauxite is not clear.Plants and their soil were collected from an abandoned karst bauxite area at Shangdong, Guizhou Province, southwestern China. Plants were collected and identified as Pteris vittata, Pinus massoniana, Miscanthus floridulus, Coriaria nepalensis, Artemisia argyi and Senecio scandens.The content of metals in plant roots were in the order: P. vittata > M. floridulus > C. nepalensis, other plants roots had no consistent pattern. Concentrations of metal in plants (P. vittata and M. floridulus) and soil were: soil > root > leaf > stem. Levels of metals in soil samples easily exceeded background values, indicating that soil had been contaminated. Al and Fe were highest in soil samples of P. vittata, with a good correlation.Results show that the metal content determined in plants is relatively high, particularly in P. vittata. Data also suggest that P. vittata colonies were able to tolerate and accumulate high levels of metal elements, which evidences their suitability for use as bioindicatord of soil metal contamination caused by mining activities. [ABSTRACT FROM AUTHOR]

Development of alleviation strategies, which enhance plant growth under heavy metal stress, is important. Inorganic (zeolite) and organic (diethylene triamine penta‐acetic acid, DTPA) amendments affecting the alleviation of lead (Pb) stress in a calcareous soil were tested by investigating leaf nutrient uptake of tomato (Lycopersicon esculentum L.) plants.Experimental quantities of lead (Pb) at 0, 50, 100 and 150 mg·kg−1 soil, zeolite (clinoptilolite) at 0%, 0.5% and 1%, and DTPA at 0, 50 and 100 mg·kg−1 soil were tested in a factorial experiment with three plant replicates.According to the anova, Pb, zeolite, DTPA and their interactions significantly affected plant concentrations of nitrogen (N), potassium (K), iron (Fe), zinc (Zn), copper (Cu), manganese (Mn) and lead (Pb). With increasing DTPA concentration at different levels of zeolite and Pb, plant concentrations of macro‐ and micronutrients significantly increased. Increasing soil Pb increased leaf Pb concentration and decreased the uptake of N, K, Fe, Zn, Cu and Mn. Although with increasing Pb concentration the uptake of macro‐ and micronutrients decreased in tomato, the use of zeolite and DTPA alleviated this stress by increasing nutrient uptake compared to the control. Interestingly, however, increased levels of zeolite and DTPA led to a decreased uptake of nutrients by plants (compared with control), indicating the absorption of such nutrients by the two amendments and their partial release for further plant use.Zeolite and DTPA may alleviate the negative effects of soil Pb on tomato growth by decreasing nutrient leaching and increasing plant nutrient uptake. [ABSTRACT FROM AUTHOR]

Aquatic macrophytes are potentially useful for phytoremediation programmes in environments contaminated by arsenic (As). Biochemical and physiological modification analyses in different plant parts are important to understand As tolerance mechanisms.The objective was to evaluate glutathione metabolism in leaves and roots of Eichhornia crassipes (Mart.) Solms treated to As. Specimens of E. crassipes were cultured for 3 days in Clark's nutrient solution containing 7 μm As. The enzymes ATP sulphurylase (ATPS), glutathione reductase (GR), glutathione peroxidase (GSH‐Px), glutathione sulphotransferase (GST) and γ‐glutamylcysteine synthetase (γ‐ECS) activity, glutathione content, total protein and non‐protein thiols were evaluated.The ATPS activity increased in roots. GR activity in leaves and GSH‐Px in roots were lower. GST activity was higher in roots and lower in leaves, and γ‐ECS activity was higher in leaves. Glutathione levels were lower, total thiol levels were higher and non‐protein levels did not change in E. crassipes leaves and roots. Exposure to As increased enzyme activity involved with sulphur metabolism, such as ATPS. Higher GR activity and lower GSH‐Px indicate increased glutathione conjugation to As due to increased GSH availability. The higher GST activity indicates its participation in As detoxification and accumulation through As GSH conjugation. Changes in glutathione and thiol levels suggest high phytochelatin synthesis.In conclusion, the increments in ATPS, GR, GST and γ‐ECS activity indicate that these enzymes are involved in GSH metabolism and are part of the E. crassipes As detoxification mechanism. [ABSTRACT FROM AUTHOR]

Upright convection can impact extratropical cyclone (ETC) precipitation and dynamics differently than isentropic ascent, but how often it occurs and how much it contributes to total precipitation within an ETC have not been systematically documented in previous literature. Herein, convection in ETCs is analyzed using ground‐based radar observations over the Eastern United States. Convection occupies 1%–5% of the precipitating region and constitutes 1%–15% of total cyclone precipitation. Furthermore, the location of convective activity occurs preferentially in the warm sector early in a cyclone's life cycle, and then as the storm evolves, more convection occurs along and behind the cold front. The precipitation rates in regions with convection are more likely to be stronger than those in other precipitating regions of the cyclone. However, the cyclones with the largest area‐average precipitation rates include only a small contribution from convection. Plain Language Summary: This research is motivated by the potential influence of convection on extratropical cyclone circulation. We utilize a newly derived dataset of upright convection and a cyclone‐tracking framework to quantify convective activity in extratropical cyclones over the United States, east of the Rocky Mountains. We find that upright convection only occupies a small portion of the precipitating region, and the relative contribution to total precipitation has relatively small variability as the cyclone evolves. We find that the location of convective activity occurs preferentially in the warm sector early in a cyclone's life cycle, and as the storm evolves, more convection occurs along and behind the cold front. We find that precipitation rates in regions with convection are more likely to be stronger than those in other precipitating regions of the cyclone. However, the cyclones with the largest area‐average precipitation rates include only a small contribution from convection. Key Points: Convection occurs in 1%–5% of precipitating regions of extratropical cyclones over eastern United States and contributes 1%–15% of total precipitationThe majority of upright convection occurs ahead of the cold front and disperses into other regions as the cyclone agesWhile convection produces larger rain rates, cyclones with greater total precipitation do not have a large convective contribution [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) is an effective way to remove heavy metals' inhibition on plants, however, few relevant research attempts have been made to determine the contribution of AMF to the physiological and biochemical changes related to the enhanced copper tolerance of Phragmites australis under metal‐stressed conditions.In this study, the effects of AMF inoculation on P. australis under different concentrations of copper stress were investigated according to the changes in the parameters related to growth and development, and photosynthetic charateristics. Then, differentially expressed proteins (DEPs) were evaluated by the Isobaric Tag for Relative and Absolute Quantification (iTRAQ) system, which could accurately quantify the DEPs by measuring peak intensities of reporter ions in tandem mass spectrometry (MS/MS) spectra.It was found that AMF inoculation may relieve the photosynthesis inhibition caused by copper stress on P. australis and thus promote growth. Proteomic analysis results showed that under copper stress, the inoculation of R. irregularis resulted in a total of 459 differently‐expressed proteins (200 up‐regulated and 259 down‐regulated) in root buds. In addition, the photosynthetic changes caused by AMF inoculation mainly involve the up‐regulated expression of transmembrane protein–pigment complexes CP43 (photosystem II) and FNR (ferredoxin‐NADP+ oxidoreductase related to photosynthetic electron transport).These results indicate that AMF could effectively improve the growth and physiological activity of P. australis under copper stress, and thus provides a new direction and instructive evidence for determining the mechanisms by which AMF inoculation enhances the copper tolerance of plants. [ABSTRACT FROM AUTHOR]

Salicylic acid‐induced protein kinase (SIPK) is known as a 'master switch' for stress responses in plants. It can be induced by salicylic acid (SA) and several stress factors. The main aim of the present study was to reveal the relationship between SA accumulation and the gene expression level of SIPK during 50 and 250 µm Cd stress in wheat plants.Quantitative real‐time PCR was used for determination of the gene expression level of SIPK. Salicylic acid content measurement was performed with an HPLC system equipped with a fluorescence detector.Cadmium treatment increased the endogenous SA level and expression level of SIPK in a concentration‐dependent manner. Induction of SIPK expression preceded the accumulation of endogenous SA. Although SA treatment induced dramatic endogenous SA accumulation, its SIPK‐inducing effect was moderate. In roots, higher induction of SIPK was observed than in leaves. The same tendency of SIPK expression was observed in both Cd‐ and SA‐treated plants, as decisively the highest transcript level was detected after 30 min of treatment, but thereafter the expression decreased rapidly to control level or even below.The induction of SIPK was transient in all cases, and even a very high SA level in either the leaves or roots was not able to maintain the elevated expression level of this gene. The results suggest that SIPK has a role in initiating Cd stress response and the exogenous SA‐induced signalling process. Salicylic acid‐induced protein kinase (SIPK) has a role in the initiation of cadmium stress response and the exogenous salicylic acid‐induced signalling process. [ABSTRACT FROM AUTHOR]

Seedling establishment is a critical step in environment colonisation by higher plants that frequently occurs under adverse conditions. Thus, we carried out an integrated analysis of seedling growth, water status, ion accumulation, reserve mobilisation, metabolite partitioning and hydrolase activity during seedling establishment of the native Caatinga species Piptadenia moniliformis (Benth.) Luckow & R.W. Jobson under salinity.Two‐day‐old seedlings were cultivated in vitro for 4 days in water agar (control) or supplemented with 50 or 100 mm NaCl. Biochemical determinations were performed according to standard spectrophotometric protocols.We found that 100 mm NaCl stimulated starch degradation, amylase activity and soluble sugar accumulation, but limited storage protein hydrolysis in the cotyledons of P. moniliformis seedlings. Although Na+ accumulation in the seedling affected K+ partitioning between different organs, it was not possible to associate the salt‐induced changes in reserve mobilisation with Na+ toxicity, or water status, in the cotyledons. Remarkably, we found that starch content increased in the roots of P. moniliformis seedlings under 100 mm NaCl, probably in response to the toxic effects of Na+.The mobilisation of carbon and nitrogen reserves is independently regulated in P. moniliformis seedlings under salt stress. The salt‐induced delay in seedling establishment and the resulting changes in the source–sink relationship may lead to storage protein retention in the cotyledons. Possibly, the intensification of starch mobilisation in the cotyledons supported starch accumulation in the root as a potential mechanism to mitigate Na+ toxicity. [ABSTRACT FROM AUTHOR]

Heavy metals are characterised by a relatively high density and cause genotoxic, cytotoxic and mutagenic effects on plants, animals and humans. Lead (Pb) is one of the heavy metals that causes toxicity to plants and animals.This experiment was conducted using a hydroponic technique to study the effects of Pb(NO3)2 on physiological, biochemical and ultrastructural characteristics in Leucaena leucocephala seedlings. Plants were grown in a growth chamber for 21 days in Hoagland's solution supplemented with 0 (control), 25, 50, 100, 300, 500 and 700 µm Pb(NO3)2.Shoot heights as well as root lengths decreased significantly in Pb‐treated plants with 300, 500 and 700 µm. In Pb‐treated plants with high Pb concentrations, photosynthesis rate (PN), stomatal conductance (gs) and transpiration rate (E) decreased. Total protein and carbohydrate content in Pb‐treated plants with 300, 500 and 700 µm increased significantly in leaves. Moreover, in Pb‐treated plants with 300, 500 and 700 µm Pb(NO3)2, mesophyll cells had enlarged chloroplasts with disrupted thylakoid membranes associated with large starch grains. In contrast, Pb treatments with 25, 50 µm and 100 µm were not toxic to the plants. Thick sections of roots of Pb‐treated plants with 300, 500 and 700 µm Pb showed distinct changes in structure of epidermal and cortical cells. Moreover, thin sections of roots of Pb‐treated plants with 300, 500 and 700 µm Pb had thickened walls of xylem cells.These results will shed more light in understanding the effects of heavy metal stress on plants. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is one of the most toxic heavy metals and a non‐essential element to all organisms, including plants; however, the genes involved in Cd resistance in plants remain poorly characterised.To identify Cd resistance genes in rice, we screened a rice cDNA expression library treated with CdCl2 using a yeast (Saccharomyces cerevisiae) mutant ycf1 strain (DTY167) and isolated two rice phytochelatin synthases (OsPCS5 and OsPCS15).The genes were strongly induced by Cd treatment and conferred increased resistance to Cd when expressed in the ycf1 mutant strain. In addition, the Cd concentration was twofold higher in yeast expressing OsPCS5 and OsPCS15 than in vector‐transformed yeast, and OsPCS5 and OsPCS15 localised in the cytoplasm. Arabidopsis thaliana plants overexpressing OsPCS5/‐15 paradoxically exhibited increased sensitivity to Cd, suggesting that overexpression of OsPCS5/‐15 resulted in toxicity due to excess phytochelatin production in A. thaliana.These data indicate that OsPCS5 and OsPCS15 are involved in Cd tolerance, which may be related to the relative abundances of phytochelatins synthesised by these phytochelatin synthases. [ABSTRACT FROM AUTHOR]

Environmental cadmium (Cd) sources have increased in mangrove sediments in recent decades, inducing cellular damage to many plants. Avicennia schaueriana is abundant in mangrove sites and has been subject to Cd contamination. The possible effects of Cd toxicity and the structural and physiological disturbances to this plant were studied. Can this plant express early cellular tolerance mechanisms to such metal contamination?Seedlings of A. schaueriana were collected from sites of their natural occurrence, placed in plastic pots containing nutrient solution for 60 days, and subsequently exposed to increasing Cd concentrations for 5 days under experimental conditions. The anatomical, ultrastructural and physiological changes induced by Cd were analysed.Cd accumulated mainly in the root system and in pneumatophores, stems and leaves, induced differential accumulation of mineral nutrients, but did not induce necrosis or changes in leaf anatomy. However, there was a decrease in starch grains and an increase in deposited electron‐dense material in the cortex and vascular bundles. Cd induced both increases in calcium (Ca) content in shoots and Ca oxalate crystal precipitation in leaf mesophyll and was detected in crystals and in the secretion of salt glands.Our observations and experimental results provide evidence of Cd tolerance in A. schaueriana. As a new feature, despite the clear cellular physiological disorders, this plant is able to eliminate Cd through leaf salt glands and immobilise it in Ca crystals, representing fast mechanisms for Cd exclusion and complexation in leaves in heavy metal coastal polluted marine ecosystems. [ABSTRACT FROM AUTHOR]

Heavy metal allocation and the mechanism(s) of metal sequestration in different clonal organs, micro‐domains and subcellular structures has not been systematically studied for rhizomatous perennial plants. It is thus pertinent to investigate knowledge of the speciation and distribution characteristics of Cu in Phragmites australis to elucidating the mobility of metals in wetland plants after their uptake via root systems so as to facilitate development of strategies to enhance Cu tolerance.This study investigated the distributions of Cu in P. australis root, stem and leaf using ICP‐MS, synchrotron‐based X‐ray micro‐fluorescence and X‐ray absorption spectroscopy, then evaluated the effects of Cu on cellular structure and ultrastructure via transmission electron microscopy.The results indicate a clear preferential localisation of Cu in the roots as compared with the shoots (stems and leaves). The intensity of Cu in the vascular bundles was higher than that in the surrounding epidermis and the endodermis and parenchyma outside the medullary cavity. The dominant chemical form of Cu in P. australis was similar to Cu citrate.The results suggest that although Cu can be easily transported into the vascular tissues in roots and stems via Cu citrate, most of the metal absorbed by plants is retained in the roots because if its high binding to the cell wall, thus preventing metal translocation to aerial parts of the plants. Therefore, P. australis showed a high capacity to accumulate Cu in roots, being therefore a suitable species for phytostabilisation interventions. [ABSTRACT FROM AUTHOR]

Calcium (Ca) signalling has an essential role in regulating plant responses to various abiotic stresses.This study applied Ca in various forms (Ca acetate and CaCl2) and concentrations to reduce cadmium (Cd) concentration in rice and propose a possible mechanism through which Ca acts to control the Cd concentration in rice.The results showed that supplementation of Cd‐contaminated soil with Ca acetate reduced the Cd concentration in rice after exposure for 7 days in both hydroponic and soil conditions. The possible involvement of the auto‐inhibited Ca2+‐ATPase gene (ACA) might act to control the primary signal of the Cd stress response. The messages from ACA3 and ACA13 tended to up‐regulate the low‐affinity cation transporter (OsLCT1) and down‐regulate Cd uptake and the Cd translocation transporter, including the genes, natural resistance‐associated macrophage protein 5 (Nramp5) and Zn/Cd‐transporting ATPase 2 (HMA2), which resulted in a reduction in the Cd concentration in rice. After cultivation for 120 days, the application of Ca acetate into Cd‐contaminated soil inhibited Cd uptake of rice.Increasing the Ca acetate concentration in the soil lowered the Cd concentration in rice shoots and grains. Moreover, Ca acetate maintained rice productivity and quality whereas both aspects decreased under Cd stress. [ABSTRACT FROM AUTHOR]

Ammonium gluconate (AG) provides both an organic carbon source and a nitrogen source, which can positively improve soil fertility and delay soil degradation.We investigated the underlying mechanisms of both NH4+‐ and C6H11O7−‐mediated resistance to high salt concentrations in maize (Zea mays L.), and how they relate to antioxidant cellular machinery, root system architecture, root activity and lignin content in roots.Seedlings treated with AG maintained lower Na+ content, higher chlorophyll content, higher CAT and POD activity, compared with those without AG and ammonium carbonate (AC). The total size of the root system, primary root length and number of lateral roots detected on the primary root treated with AG decreased compared with those not treated with AG at the same NaCl concentration. However, average root diameter and root activity when treated with AG were significantly higher than roots without AG at the same NaCl concentration. Furthermore, total size of the root system, primary root length and number of lateral roots detected on primary rootsof seedlings treated with AG were higher than those treated with AC at the same NaCl concentration.These results suggested that AG may be a good organic fertiliser under salt stress by decreasing Na+ content and increasing chlorophyll content, activity of antioxidant enzymes, root diameter and root activity in maize seedlings. [ABSTRACT FROM AUTHOR]

Pogonatherum crinitum is a promising lead (Pb) hyperaccumulator due to its high Pb tolerance and accumulation ability. However, the mechanisms that support Pb accumulation and tolerance in P. crinitum are not yet clearly understood.An indoor hydroponic experiment was conducted by cultivating P. crinitum seedlings exposed to intermittent Pb stress for 60 days, divided into four stages (T1, T2, T3 and T4), with a 15‐day duration per stage. The following concentrations of Pb were used: 0, 500, 0, 500 mg·l−1 and 0, 1000, 0, 1000 mg·l−1). Antioxidant enzyme activity, Pb concentration and subcellular distribution of Pb were measured at each of the above stages.The results showed that superoxide dismutase (SOD) activity in shoots, and SOD, peroxidase (POD) and malondialdehyde (MDA) activity in shoots and roots significantly increased from T1 (no Pb stress) to T2 (Pb stress) in both 500 mg·l−1 and 1000 mg·l−1 treatments; however, no significant difference was noted between stages T3 (no Pb stress) and T4 (Pb stress). There was no obvious effect of Pb stress on catalase (CAT) activity in shoots and roots among different stages. The Pb concentration in shoots was up to 5090.90 mg·kg−1 and 7573.57 mg·kg−1, and the bioconcentration factor (BFC) was 10.18 and 7.57 for the 500 mg·l−1 and 1000 mg·l−1 treatments, respectively, which confirmed the Pb hyperaccumulator characteristics of P. crinitum. For plants under Pb stress, most of the Pb was fixed in the cell walls, with a smaller amount in leaves and root vacuoles.Both SOD and POD scavenging of reactive oxygen radicals and fixing and compartmentalisation of Pb in the cell wall might play important roles in detoxification of P. crinitum seedlings in response to Pb stress. There was no phased response of P. crinitum to intermittent Pb stress and the physiological response to Pb stress may be contiguous. [ABSTRACT FROM AUTHOR]

In most plant species, a rapid increase in free proline content occurs following exposure to hyperosmotic stress conditions. However, inconsistent results were reported concerning the role of such an increase on the plant response to water shortage or excess salt. Therefore, the possibility that proline accumulation may help the cell to withstand stress conditions, or that it simply represents a stress marker, is still a matter of debate. A possible relationship between proline accumulation and salt tolerance was investigated in a set of 17 Italian rice varieties.Rice seedlings were exposed to increasing salt concentrations during germination and early growth. The resulting levels of free proline were measured separately in shoots and roots and compared to those in untreated controls. Results were related to the corresponding ability of a given genotype to tolerate stress conditions.Neither absolute proline levels in untreated or in salt‐stressed seedlings showed a straightforward relationship to the relative tolerance to salt, estimated as conductivity values able to reduce growth by 10 or 50%. Conversely, a highly significant correlation was found between the increase in proline levels in shoots and the ability to withstand stress.The results strengthen a recent hypothesis suggesting than an increase in proline metabolic rates, more than the resulting proline content, may help the cell to counteract the effects of abiotic stress conditions. [ABSTRACT FROM AUTHOR]

Phytolacca americana is recognised as a hyperaccumulator that accumulates cadmium (Cd) and manganese (Mn). Although most studies have provided abundant physiological evidence, little is known about the molecular mechanisms of Cd accumulation in P. americana.In this study, Cd‐induced genes were isolated using suppression subtractive hybridisation (SSH) library construction, and gene expression patterns under Cd stress were quantified using real‐time quantitative PCR. The functions of PaGST, PaMT and PaFe‐SOD were confirmed in transformant yeast. Reactive oxygen species (ROS) formation and cell death in root tips were detected, and SOD and POD activities in leaf tissue were also analysed.There were about 447 expressed sequence tags (ESTs) identified and confirmed. GO analysis showed those genes were mainly involved in metabolism, cell stress and defence, transcription and translation, signal transduction, transport, energy and ion transport, which formed the basis for a molecular understanding of P. americana Cd tolerance mechanisms. Cd also stimulated ROS formation and modified the antioxidant systems.Taken together, our results indicate that ROS formation and Cd‐induced gene expression favour P. americana tolerance by activating the defence system and permitting subsequent adaptation to Cd toxicity. [ABSTRACT FROM AUTHOR]