Phytoremediation efficiency of poplar hybrid varieties with diverse genetic backgrounds in soil contaminated by multiple toxic metals (Cd, Hg, Pb, and As).

Fifteen poplar varieties were used in a field trial to investigate the phytoremediation efficiency, stress resistance, and wood property of poplar hybrid varieties with diverse genetic backgrounds under the composite pollution of heavy metals. The coefficient of variation and clone repeatability for growth traits and Cd concentration were large. The Cd accumulation of poplar varieties 107 and QHQ reached 1.9 and 1.7 mg, respectively, followed by QHB, Ti, 69, and Pa, in which Cd accumulation reached 1.3 mg. Most of the intra-specific hybrid varieties (69, QH1, SL4, T3, and ZL46) had low Cd concentrations and small biomass, resulting in weak Cd accumulation and low phytoremediation efficiency for Cd-polluted soil. By contrast, the inter-sectional and inter-specific hybrid varieties exhibited better growth performance and accumulated higher concentrations of heavy metals than the intra-specific hybrids. The bioconcentration factor and translocation factor of Hg, As, and Pb were less than 1, indicating that poplars have low phytoremediation efficiency for these heavy metals. The hybrids between section Aigeiros and Tacamahaca (QHQ and QHB) and the inter-specific hybrid 107 within section Aigeiros were more resistant to composite heavy metal stress than the other poplar varieties were partially because of their high levels of free proline that exceeded 93 µg·g-1 FW. According to the correlation analysis of the concentrations of the different heavy metals, the poplar roots absorbed different heavy metals in a cooperative manner, indicating that elite poplar varieties with superior capacity for accumulating diverse heavy metals can be bred feasibly. Compared with the intra-specific hybrid varieties, the inter-sectional (QHQ and QHB) and inter-specific (107) hybrid varieties had higher pollution remediation efficiency, larger biomass, higher cellulose content, and lower lignin content, which is beneficial for pulpwood. Therefore, breeding and extending inter-sectional (QHQ and QHB) and inter-specific hybrid varieties can improve the phytoremediation of composite pollution.

Characterization and epidemiologic analysis of mycoplasmal pneumonia of sheep in Qinghai Province.

Mycoplasmal pneumonia in sheep and goats usually result covert but huge economic losses in the sheep and goat industry. The disease is prevalent in various countries in Africa and Asia. Clinical manifestations in affected animals include anorexia, fever, and respiratory symptoms such as dyspnea, polypnea, cough, and nasal discharge. Due to similarities with other respiratory infections, accurate diagnosis can be challenging, and isolating the causative organism is often problematic. However, the utilization of molecular techniques, such as PCR, allows for rapid and specific identification of pathogens. Thus, a goat infection model with Mycoplasma was established and the pathogen was tested using PCR. The results indicated that this approach could be effectively utilized for the rapid detection of mycoplasma in clinical settings. Additionally, the prevalence of contagious pleuropneumonia of sheep in Qinghai Province was further investigated through PCR analysis. A total of 340 nasal swabs were collected from 17 sheep farms in Qinghai province. Among these samples, 84 tested positive for Mycoplasma mycoides subsp. capri (Mmc) and 148 tested positive for Mycoplasma ovipneumoniae (Movi), resulting in positive rates of 24.71% and 43.53% respectively. Furthermore, our investigation revealed positive PCR results for nasal swabs, trachea, and lung samples obtained from sheep exhibiting symptoms suggestive of mycoplasma infection. Moreover, three distinct strains were isolated from these positive samples. Additionally, the inflammatory cytokines of peripheral blood mononuclear cells (PBMCs) were assessed using RT-PCR. The findings demonstrated a high susceptibility of sheep to Movi in Qinghai province, with infected sheep displaying an inflammatory response. Consequently, the outcomes of this study will furnish valuable epidemiological insights for the effective prevention and control of this disease within Qinghai Province.

Effects of nitrate- and ammonium- nitrogen on anatomical and physiological responses of Catalpa bungei under full and partial root-zone drought.

Catalpa bungei is a precious timber species distributed in North China where drought often occurs. To clarify adaptive responses of C. bungei to partial- and full- root-zone drought under the influence of nitrogen forms, a two-factor experiment was conducted in which well-watered (WW), partial root-zone drought in horizontal direction (H-PRD) and in vertical direction (V-PRD), and full root-zone drought (FRD) were combined with nitrate-nitrogen (NN) and ammonium-nitrogen (AN) treatments. C. bungei responded to FRD by sharply closing stomata, decreasing gas exchange rate and increasing leaf instantaneous water use efficiency (WUEi). Under FRD condition, the growth of seedlings was severely inhibited and the effect of N forms was covered up by the drastic drought effect. In comparison, stomata conductance and gas exchanges were moderately inhibited by PRDs. WUEi in V-PRD treatment was superior to H-PRD due to the active stomata regulation resulting from a higher ABA level and active transcription of genes in abscisic acid (ABA) signaling pathway under V-PRD. Under both PRDs and FRD, nitrate benefited antioxidant defense, stomata regulation and leaf WUEi. Under V-PRD, WUEi in nitrate treatment was superior to that in ammonium treatment due to active stomata regulation by signaling network of nitric oxide (NO), Ca2+ and ABA. Under FRD, WUEi was higher in nitrate treatment due to the favoring photosynthetic efficiency resulting from active NO signal and antioxidant defense. The interactive effect of water and N forms was significant on wood xylem development. Superoxide dismutase (SOD) and catalase (CAT) largely contributes to stress tolerance and xylem development.

Vegetation-environment interactions: plant species distribution and community assembly in mixed coniferous forests of Northwestern Himalayas.

One of the main goals of ecological studies is to disentangle the dynamics that underlie the spatiotemporal distribution of biodiversity and further functions of the ecosystem. However, due to many ecological and geopolitical reasons, many remote areas with high plant species diversity have not been assessed using newly based analytical approaches for vegetation characterization. Here, we classified and characterized different vegetation types (i.e., major plant communities) based on indicator species and on the influence of different environmental gradients in the Himalayan mixed coniferous forest, Pakistan. For that, we addressed the following questions: Does the vegetation composition of the Himalayan mixed coniferous forest correlate with climatic, topographic, geographic, and edaphic variables? Is it possible to identify plant communities through indicator species in relation to environmental gradients using multivariate approaches? Can this multivariate be helpful for conservation planning? During four consecutive years we assessed the vegetation composition and environmental variables (21 variables divided in geographic, climatic, topographic, and edaphic groups) of 156 50 m-trasects between an elevation of 2000-4000 m. Using newly based analytical approaches for community characterization, we found a total of 218 plant species clustered into four plant communities with the influence of environmental gradients. The highest index of similarity was recorded between Pinus-Cedrus-Viburnum (PCV) and Viburnum-Pinus-Abies (VPA) communities, and the highest index of dissimilarity was recorded between PCV and Abies-Juniperus-Picea (AJP) communities. Among these four communities, highest number of plant species (156 species) was recorded in PCV, maximum alpha diversity (H' = 3.68) was reported in VPA, highest Simpson index (0.961) and Pielou's evenness (0.862) were reported in VPA and AJP. The edaphic gradients (i.e., organic matter, phosphorous, pH and soil texture) and climatic factors (temperature, humidity) were the strongest environmental gradients that were responsible for structuring and hosting the diverse plant communities in mixed coniferous forest. Finally, the Himalayan mixed coniferous structure is more influenced by the spatial turnover beta-diversity process (ßsim) than by the species loss (nestedness-resultant, ßsne). Our analysis of the vegetation structure along the environmental gradient in the Himalayan mixed coniferous forest supported by sophisticated analytical approaches reveled indicator species groups, which are associated to specific microclimatic zones (i.e., vegetation communities). Within this focus, we side with the view that these results can support conservation planning and management for similar and different areas providing mitigating and preventive measures to reduce potential negative impacts, such as anthropic and climatic.

Phylogeny and population structure of Echinococcus granulosus (sensu stricto) based on full-length cytb-nad2-atp6 mitochondrial genes - First report from Sialkot District of Pakistan.

Cystic echinococcosis is a zoonotic disease of livestock having serious economic setbacks. The etiological agents of the disease belong to Echinococcus granulosus sensu lato. Despite of worldwide distribution of the disease, the molecular studies mainly employ amplification of cox1, nad1 and nad5 genes. To further strengthen the knowledge about significance of other molecular markers and to investigate the genetic diversity and population structure of Echinococcus species in Pakistan, the current study was designed in which full length mitochondrial cytb, atp6 and nad2 genes were amplified. Based on BLAST searches of the generated cytb, atp6 and nad2 gene sequences from a total of 18 hydatid cysts collected from cattle, 12 isolates were identified as E. granulousus G3 and 6 as E. granulosus (G1). The phylogeny inferred by the Bayesian method using nucleotide sequences of cytb-atp6-nad2 further confirmed their identity. The diversity indices indicated a high haplotype and a low nucleotide diversity. The negative values of Tajima's D and Fu's Fs test demonstrated deviation from neutrality suggesting a recent population expansion. To the best of our knowledge, the present study described the genetic variation of E. granulosus population for the first time in Pakistan using full-length cytb, atp6 and nad2 mitochondrial genes. The findings on the genetic variation of E. granulosus in Pakistan will constitute useful baseline information for future studies on the prevalence and population structure of E. granulosus based on full-length cytb, atp6 and nad2.

Natural selection pressure exerted on "Silent" mutations during the evolution of SARS-CoV-2: Evidence from codon usage and RNA structure.

From the first emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) till now, multiple mutations that caused synonymous and nonsynonymous substitutions have accumulated. Among them, synonymous substitutions were regarded as "silent" mutations that received less attention than nonsynonymous substitutions that cause amino acid variations. However, the importance of synonymous substitutions can not be neglected. This research focuses on synonymous substitutions on SARS-CoV-2 and proves that synonymous substitutions were under purifying selection in its evolution. The evidence of purifying selection is provided by comparing the mutation number per site in coding and non-coding regions. We then study the two forces of purifying selection: synonymous codon usage and RNA secondary structure. Results show that the codon usage optimization leads to an adapted codon usage towards humans. Furthermore, our results show that the maintenance of RNA secondary structure causes the purifying of synonymous substitutions in the structural region. These results explain the selection pressure on synonymous substitutions during the evolution of SARS-CoV-2.

The growth curve determination and economic trait correlation for Qinchuan bull population.

Carcass weight, as a measure of meat yield, and body measurements are directly correlated traits in livestock. However, longitudinally collected phenotype records of local breeds are not comprehensive. The research was performed on Qinchuan bull population to understand their growth and development, and data from Qinchuan bull that was weighed and measured at birth, 6, 12, 18, and 24 months of age was analyzed. Furthermore, Logistic, Brody, Gompertz, and Bertallanffy were used to fit the growth curves for weight and body size traits. The results showed that the four curve models have good fitting degrees for the weight and body size (R2 > 0.99), and the Bertallanffy model exhibited a good fit to the measured data of body weight, and the model estimated the inflection point of body weight as (5.43 months of age, 122.01 kg). Particularly, the limited mature body weight can reach 557.8 kg by the Brody model. Body weight was significantly positively correlated with body height, hip height, body length, chest circumference, abdominal girth, and calf girth (p < 0.0001), and the correlation between body weight and body length was the highest (r = 0.975). The regression equation predicting body weight was Y = -275.691 + 3.28 X3 + 1.311 X4 - 0.397 X5.

Analysis of codon usage bias of lumpy skin disease virus causing livestock infection.

Lumpy skin disease virus (LSDV) causes lumpy skin disease (LSD) in livestock, which is a double-stranded DNA virus that belongs to the genus Capripoxvirus of the family Poxviridae. LSDV is an important poxvirus that has spread out far and wide to become distributed worldwide. It poses serious health risks to the host and causes considerable negative socioeconomic impact on farmers financially and on cattle by causing ruminant-related diseases. Previous studies explained the population structure of the LSDV within the evolutionary time scale and adaptive evolution. However, it is still unknown and remains enigmatic as to how synonymous codons are used by the LSDV. Here, we used 53 LSDV strains and applied the codon usage bias (CUB) analysis to them. Both the base content and the relative synonymous codon usage (RSCU) analysis revealed that the AT-ended codons were more frequently used in the genome of LSDV. Further low codon usage bias was calculated from the effective number of codons (ENC) value. The neutrality plot analysis suggested that the dominant factor of natural selection played a role in the structuring of CUB in LSDV. Additionally, the results from a comparative analysis suggested that the LSDV has adapted host-specific codon usage patterns to sustain successful replication and transmission chains within hosts (Bos taurus and Homo sapiens). Both natural selection and mutational pressure have an impact on the codon usage patterns of the protein-coding genes in LSDV. This study is important because it has characterized the codon usage pattern in the LSDV genomes and has provided the necessary data for a basic evolutionary study on them.

Ethnic practices in treating skin diseases: The traditional dermatologist's role.

This study documents the role of traditional medicinal and therapeutic plants in treating various skin ailments by indigenous communities of the tribal district of North Waziristan, Pakistan. A total of 130 informants and traditional dermatologists were interviewed. They employed 77 plant species belonging to 49 families to treat various skin ailments. The leading life form reported was herbs (41 species), whereas the dominant family was Lamiaceae (5 species). Leaves were the most commonly used plant part (37 species). The most preferred mode of preparation was paste (30.38%), and the dominant mode of administration was topical (69.23%). Important medicinal plants reported in this study are recommended for further phytochemical screening for bioactive constituents, which may lead to novel drug discoveries.

S100A10 might be a novel prognostic biomarker for head and neck squamous cell carcinoma based on bioinformatics analysis.

Head and neck squamous cell carcinoma (HNSCC) is a frequent malignant tumor of the head and neck with a dismal survival probability due to relapse and metastasis. S100As have been identified as being involved in the tumor procession of various cancer types. However, the expressions of S100As in HNSCC and their prognostic relevance are unknown. Bioinfromatics analysis was conducted to identify the prognostic value and function of S100As in HNSCC patients. In the study, we found that high mRNA expression levels of S100A3, S100A4, S100A7A, S100A9, and low mRNA expression levels of S100A1, S100A10 were related with a good overall survival in HNSCC patients. Importantly, the prognosis model suggested that S100A10 may have a certain impact on the development of HNSCC. Moreover, single-cell RNA sequencing analysis clarified that the specific functions of S100A10 had positive regulatory effects on metastasis, blood vessel generation, EMT, hypoxia, and invasion. Our findings implied that S100A10 might be a new prognostic biomarker for HNSCC, and played a role in promoting the occurrence, and development of HNSCC.

Ethnogynaecological Knowledge of Traditional Medicinal Plants Used by the Indigenous Communities of North Waziristan, Pakistan.

Background: Since the beginning of civilization, medicinal plants have been used in human healthcare systems. Studies have been conducted worldwide to evaluate their efficacy, and some of the results have triggered the development of plant-based medications. Rural women in Pakistan frequently experience gynaecological disorders due to malnutrition and heavy physical work during pregnancy. Due to the low economic status, the remoteness of the area, and the lack of modern health services, herbal therapy for gynaecological disorders is common among the indigenous tribes of the study area. Methods: Field surveys were carried out from April 2018 to October 2020 to collect data regarding medicinal plants used for different gynaecological disorders. A semistructured questionnaire was used to collect ethnogynaecological data. Results: In total, 67 medicinal plant species belonging to 38 families are being used to treat 26 different gynaecological problems. The herbaceous growth form and the Lamiaceae family were recorded with the maximum number of plant species (42 species and 7 species, respectively). Leaves are the most highly utilized plant part, with 16 species. In the case preparation method, decoction was the dominant method (25 species, 36.76%). The informants reported the maximum number of species for the treatment of irregular menstrual flow as 11 species (15.28%). The highest relative frequency of citation (RFC) value was obtained for Acacia modesta (0.37), and the use value (UV) for Tecomella undulata (0.85). The highest informants' consensus factor (ICF) value (1.0) was obtained for emmenagogue and tonic each after delivery. The highest consensus index (CI%) value was calculated for Acacia modesta (36.92%). The Lamiaceae had the highest family importance value (FIV) (98.46%). Conclusion: This is the first ever quantitative study focusing mainly on ethnogynaecological study conducted in the tribal areas of North Waziristan which highlights the importance of traditional herbal remedies for their basic medical requirements. The results of this study would serve as a baseline for advanced phytochemical and pharmacological screening, as well as conservationists for further studies.

Genetic diversity and population structure of Cinnamomum balansae Lecomte inferred by microsatellites.

Cinnamomum balansae Lecomte (Lauraceae), an economically important forest tree, is distributed in the tropical forests of central and northern Vietnam, which has been threatened in recent decades due to the destruction of its habitat and over-exploitation. The genetic diversity and population structure of the species have not been fully evaluated. We used a set of 15 microsatellites to analyze 161 adult trees from 9 different populations, representing the geographical distribution of C. balansae. Ninety-two different alleles were identified. Here our results showed a low genetic diversity level with an average H o = 0.246 and H e = 0.262, and a high level of genetic differentiation (F ST = 0.601). The bottleneck tests indicated evidence of a reduction in the population size of the two populations (TC and CP). Additionally, all three clustering methods (Bayesian analysis, principal coordinate analysis, and Neighbor-joining tree) were identified in the two genetic groups. The Mantel test showed a significant positive correlation between genetic distance and geographic distance (R 2 = 0.7331). This study will provide a platform for the conservation of C. balansae both in ex-situ and in-situ plans.

Evolution of codon usage in Taenia saginata genomes and its impact on the host.

The beef tapeworm, also known as Taenia saginata, is a zoonotic tapeworm from the genus Taenia in the order Cyclophyllidea. Taenia saginata is a food-borne zoonotic parasite with a worldwide distribution. It poses serious health risks to the host and has a considerable negative socioeconomic impact. Previous studies have explained the population structure of T. saginata within the evolutionary time scale and adaptive evolution. However, it is still unknown how synonymous codons are used by T. saginata. In this study, we used 90 T. saginata strains, applying the codon usage bias (CUB). Both base content and relative synonymous codon usage (RSCU) analysis revealed that AT-ended codons were more frequently used in the genome of T. saginata. Further low CUB was observed from the effective number of codons (ENC) value. The neutrality plot analysis suggested that the dominant factor of natural selection was involved in the structuring of CUB in T. saginata. Further analysis showed that T. saginata has adapted host-specific codon usage patterns to sustain successful replication and transmission chains within hosts (Bos taurus and Homo sapiens). Generally, both natural selection and mutational pressure have an impact on the codon usage patterns of the protein-coding genes in T. saginata. This study is important because it characterized the codon usage pattern in the T. saginata genomes and provided the necessary data for a basic evolutionary study on them.

A detailed comparative analysis of codon usage bias in Alongshan virus.

Alongshan virus (ALSV) is an emerging tick-borne pathogen that infects humans, causing febrile disease. ALSV uses Ixodes Persulcatus ticks to infect humans with a wide range of signs, from asymptomatic to encephalitis-like syndrome. There is an increasing public health concern about the ALSV infection. To get insight into the impacts of viral relations with their hosts on viral ability, survival, and evasion from hosts immune systems remain unknown. The codon usage is a driving force in viral genome evolution; therefore, we enrolled 41 ALSV strains in codon usage analysis to elucidate the molecular evolutionary dynamics of ALSV. The results indicate that the overall codon usage among ALSV isolates is relatively similar and slightly biased. Base compositions for the cds were in order of G >A >C >U and in the third position of codons G3 >A3 >C3 >T3. The RSCU values revealed that the more frequently used codons were mostly GC ended. Different codon preferences in ALSV genes in relation to codon usage of H. sapiens and Ixodes Persulcatus genes were found. Neutrality plot was determined to reveal the superiority of natural selection over directional mutation pressure in causing CUB based on GC12 versus GC3 contents. The results of these studies suggest that the emergence of ALSV in China, Russia and Finland may also be reflected in ALSV codon usage. Altogether, the presence of both mutation pressure and natural selection effect in shaping the codon usage patterns of ALSV.

Analysis of codon usage patterns and influencing factors in rice tungro bacilliform virus.

Rice tungro bacilliform virus (RTBV) belongs to genus Tungrovirus within the family Caulimoviridae harbors circular double-stranded DNA (dsDNA). Rice tungro disease (RTD) caused by RTBV, responsible for severe rice yield losses in South and Southeast Asia. Here, we performed a systematic evolutionary and codon usage bias (CUB) analysis of RTBV genome sequences. We analysed different bioinformatics techniques to calculate the nucleotide compositions, the relative synonymous codon usage (RSCU), and other indices. The results indicated slightly or low codon usage bias in RTBV isolates. Mutation and natural selection pressures have equally contributed to this low codon usage bias. Additionally, multiple factors such as host, geographical distribution also affect codon usage patterns in RTBV genomes. RSCU analysis revealed that RTBV shows mutation bias and prefers A and U ended codons to code amino acids. Codon usage patterns of RTBV were also found to be influenced by its host. This indicates that RTBV have evolved codon usage patterns that are specific to its host. The findings from this study are expected to increase our understanding of factors leading to viral evolution and fitness with respect to hosts and the environment.

Phosphorus deficiency induces root proliferation and Cd absorption but inhibits Cd tolerance and Cd translocation in roots of Populus × euramericana.

To disclose how phosphorus deficiency influence phytoremediation of Cd contamination using poplars, root architecture, Cd absorption, Cd translocation and antioxidant defense in poplar roots were investigated using a clone of Populus × euramericana. Root growth was unaltered by Cd exposure regardless of P conditions, while the degree of root proliferation upon P deficiency was changed by high level of Cd exposure. The concentration and content of Cd accumulation in roots were increased by P deficiency. This can be partially explained by the increased expression of genes encoding PM H + -ATPase under the combined conditions of P deficiency and high Cd exposure, which enhanced Cd2+-H+ exchanges and led to an increment of Cd uptake under P deficiency. Despite of the increasing Cd accumulation in roots, the translocation of Cd from roots to aerial tissues sharply decreased upon P deficiency. The relative expression of genes responsible for Cd translocation (HMA4) decreased upon P deficiency and thus inhibited Cd translocation via xylem. GR activity was decreased by P deficiency, which can inhibit the form of GSH and GSH-Cd complexes and decrease Cd translocation via GSH-Cd complexes. The transportation of PC-Cd complexes into vacuole decreased under P deficiency as a result of the low expression of PCS and ABCC1, and thus suppressed Cd tolerance and Cd detoxification in roots. Moreover, P deficiency decreased the levels of antioxidase (GR and CAT) and phytohormones including JA, ABA and GA3, which synchronously reduced antioxidant capacity in roots.

Codon Usage Bias Analysis of Bluetongue Virus Causing Livestock Infection.

Bluetongue virus (BTV) is a double-stranded RNA virus with multiple segments and belongs to the genus Orbivirus within the family Reoviridae. BTV is spread to livestock through its dominant vector, biting midges of genus Culicoides. Although great progress has been made in genomic analyses, it is not fully understood how BTVs adapt to their hosts and evade the host's immune systems. In this study, we retrieved BTV genome sequences from the National Center for Biotechnology Information (NCBI) database and performed a comprehensive research to explore the codon usage patterns in 50 BTV strains. We used bioinformatic approaches to calculate the relative synonymous codon usage (RSCU), codon adaptation index (CAI), effective number of codons (ENC), and other indices. The results indicated that most of the overpreferred codons had A-endings, which revealed that mutational pressure was the major force shaping codon usage patterns in BTV. However, the influence of natural selection and geographical factors cannot be ignored on viral codon usage bias. Based on the RSCU values, we performed a comparative analysis between BTVs and their hosts, suggesting that BTVs were inclined to evolve their codon usage patterns that were comparable to those of their hosts. Such findings will be conducive to understanding the elements that contribute to viral evolution and adaptation to hosts.

Exploring the evolutionary dynamics of Rhizobium plasmids through bipartite network analysis.

The genus Rhizobium usually has a multipartite genome architecture with a chromosome and several plasmids, making these bacteria a perfect candidate for plasmid biology studies. As there are no universally shared genes among typical plasmids, network analyses can complement traditional phylogenetics in a broad-scale study of plasmid evolution. Here, we present an exhaustive analysis of 216 plasmids from 49 complete genomes of Rhizobium by constructing a bipartite network that consists of two classes of nodes, the plasmids and homologous protein families that connect them. Dissection of the network using a hierarchical clustering strategy reveals extensive variety, with 34 homologous plasmid clusters. Four large clusters including one cluster of symbiotic plasmids and two clusters of chromids carrying some truly essential genes are widely distributed among Rhizobium. In contrast, the other clusters are quite small and rare. Symbiotic clusters and rare accessory clusters are exogenetic and do not appear to have co-evolved with the common accessory clusters; the latter ones have a large coding potential and functional complementarity for different lifestyles in Rhizobium. The bipartite network also provides preliminary evidence of Rhizobium plasmid variation and formation including genetic exchange, plasmid fusion and fission, exogenetic plasmid transfer, host plant selection, and environmental adaptation.

Phosphorus influence Cd phytoextraction in Populus stems via modulating xylem development, cell wall Cd storage and antioxidant defense.

The soils in mining lands with cadmium (Cd) contamination usually are deficient in nutrients. Disclosing how P nutrition and N:P stoichiometric ratio influences Cd accumulation and stress tolerance in stems of Populus spp. will facilitate the phytoremediation of mining sites polluted by Cd. In this study, investigations at the anatomical and physiological levels were conducted using a clone of Populus × euramericana. Both phosphorus deficiency and cadmium exposure inhibited xylem development via reducing cell layers in the xylem. Under P-sufficient condition, appropriate P status and balanced N:P ratio in stem promoted xylem development under Cd exposure via stimulating cell division, which enhanced Cd accumulation in stems. Cd accumulation in cell walls of collenchyma tissues of the stem was enhanced by P application due to increased polysaccharide production and cell wall affinity for Cd. The low P concentrations (0.3-0.4 mg g-1) and imbalanced N:P ratio under P deficiency inhibited the production of APX and ascorbate-GSH cycle, which increased oxidative stress and lipid peroxidation as indicated by high MDA concentration in stem. Under P-sufficient condition, the interactions between phytohormones and antioxidants play crucial roles in the process of antioxidant defense under Cd exposure. In conclusions, appropriate P addition and balanced N:P ratio enhanced secondary xylem development and promoted cadmium accumulation and stress tolerance in Populus stems, which can benefit the phytoextraction of Cd from Cd-contaminated soil.

Influence of nitrogen availability on Cd accumulation and acclimation strategy of Populus leaves under Cd exposure.

Nitrogen (N) plays crucial roles in chlorophyll concentration, photosynthesis, and stress tolerance of plant leaves. This study conducted a greenhouse experiment combined with Cd and N treatments to elucidate the mechanism underlying the influence of N on Cd accumulation and acclimation strategy in Populus leaves. Chlorophyll concentration and net photosynthetic rates (A) in leaves were unaltered by Cd exposure regardless of N condition. Nitrogen availability alter acclimation strategy of poplar leaves under cadmium exposure. Under sufficient N, Cd accumulation in leaves was elevated with increased intensity and duration of Cd exposure; Cd accumulation reached ca. 28 µg g-1 dry weight and 260 µg plant-1 after 60 days of exposure to high level of Cd (20 mg Cd kg-1 soil), and this finding indicates a large potential for Cd phytoextraction. Poplar leaves exhibited high capacity for antioxidant defense and stress tolerance and avoided oxidative damage under high Cd exposure. The levels of phytohormones and antioxidants in leaves and the relative expressions of critical genes encoding antioxidant enzymes were up-regulated under sufficient N condition. Nitrogen deficiency decreased chlorophyll concentration and net photosynthetic rates (A) and interfered with the production of N metabolites, resulting in a low level of phytohormones and antioxidants that are responsible for stress tolerance. The low levels of Cd accumulation in leaves may be a self-protecting strategy to prevent severe oxidative damage due to the decreased capacities for stress tolerance under N deficiency.