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Abstract: Catalase (CAT), an important enzyme of antioxidant system, was investigated the role in preventing the plant from Cd-induced oxidative stress caused by reactive oxygen species. A CAT gene from Brassica juncea was cloned and up-regulated in response to Cd/Zn. The CAT cDNA (BjCAT3) under the control of CaMV35S promoter was introduced into tobacco via Agrobacterium-mediated transformation. Northern blot analysis verified the BjCAT3 was expressed at high level in different transgenic lines. In morphological observation, we found that seedlings from transgenic tobacco plants grew better and showed longer root length in the presence of Cd versus wild-type (WT) seedlings. Under 100μM Cd stress, WT plants became chlorotic and almost dead while transgenic tobacco plants still remained green and phenotypically normal. The CAT activity of transgenic T1 generations was approximately two-fold higher than that of WT plants. In WT, endogenous CAT activity is rapidly reduced as a result of 200μM CdCl2 exposure. Compared with WT plants, lower level of Cd-induced H2O2 accumulation and cell death were detected in roots of transgenic plants with high level of CAT activity. All our findings strongly support that overexpressing BjCAT3 in tobacco could enhance the tolerance under Cd stress. [Copyright &y& Elsevier]

A clone of PvSR6 encoding a new member of the DnaJ-like protein family was isolated from a mercuric-chloride-treated bean (Phaseolus vulgaris L.) cDNA library by differential screening using cDNAs derived from treated and untreated plants. The predicted protein contains the highly conserved J domain only, which is present in all DnaJ-like proteins and is considered to play a critical role in DnaJ protein-protein interaction. PvSR6 gen is constitutively expressed in roots but weakly expressed in stems and leaf tissue. Northern blot analysis revealed the transcripts of PvSR6 were at low levels in unstressed bean leaves, but the genes expression was strongly stimulated by heavy metals. These suggest that the PvSR6 might play an important role in resistance to the damage caused by heavy metals. [ABSTRACT FROM AUTHOR]

Key message: CIPAS8 is a novel Cd-influx and Co-efflux transporters, and Ser86 and Cys128 might play a decisive role in Co-binding and translocation. Cadmium (Cd) is among the most toxic heavy metals and is a widespread environmental pollutant. Cobalt (Co) is a mineral nutrient that is essential for plant growth and development, but high concentrations may be toxic. Cadmium-induced protein AS8 (CIPAS8) is widely distributed among plant species and might be induced by heavy metals, but its function has not been studied previously. In this study, Populus euphratica PeCIPAS8 and Salix linearistipularis SlCIPAS8 were investigated. The transcription of both genes was significantly enhanced under Cd and Co stresses. PeCIPAS8 and SlCIPAS8 conferred sensitivity to Cd in transgenic yeast, allowing higher quantities of Cd to accumulate within the cells, whereas SlCIPAS8 also conferred tolerance to Co and reduced Co accumulation. The determinants of substrate selectivity of the SlCIPAS8 protein were examined by site mutagenesis, which indicated that the Ser at 86th (S86) substituted for Arg (R) [S86R] and Cys at 128th (C128) substituted for Ser [C128S] mutations limited the protein's capability for Co translocation. These results suggested that PeCIPAS8 and SlCIPAS8 may be involved in Cd uptake into the plant cell. SlCIPAS8 can reduce excess Co accumulation to maintain intracellular Co homeostasis, and the site mutations S86R and C128S were essential for Co transport. These findings provide insight into the function of CIPAS8 and highlight its potential for utilization in phytoremediation applications. [ABSTRACT FROM AUTHOR]

An endoplasmic reticulum-associated degradation–related E2–E3 pair affects grain size in rice through the brassinosteroid signaling pathway. Grain size is an important agronomic trait, but our knowledge about grain size determination in crops is still limited. Endoplasmic reticulum (ER)–associated degradation (ERAD) is a special ubiquitin proteasome system that is involved in degrading misfolded or incompletely folded proteins in the ER. Here, we report that SMALL GRAIN 3 (SMG3) and DECREASED GRAIN SIZE 1 (DGS1), an ERAD-related E2–E3 enzyme pair, regulate grain size and weight through the brassinosteroid (BR) signaling pathway in rice (Oryza sativa). SMG3 encodes a homolog of Arabidopsis (Arabidopsis thaliana) UBIQUITIN CONJUGATING ENZYME 32, which is a conserved ERAD-associated E2 ubiquitin conjugating enzyme. SMG3 interacts with another grain size regulator, DGS1. Loss of function of SMG3 or DGS1 results in small grains, while overexpression of SMG3 or DGS1 leads to long grains. Further analyses showed that DGS1 is an active E3 ubiquitin ligase and colocates with SMG3 in the ER. SMG3 and DGS1 are involved in BR signaling. DGS1 ubiquitinates the BR receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1) and affects its accumulation. Genetic analysis suggests that SMG3, DGS1, and BRI1 act together to regulate grain size and weight. In summary, our findings identify an ERAD-related E2–E3 pair that regulates grain size and weight, which gives insight into the function of ERAD in grain size control and BR signaling. [ABSTRACT FROM AUTHOR]

Reynoutria japonica Houtt., a traditional medicine herb of the Polygonaceae family, has been used since ancient times in China due to its various pharmacological effects. Chloroplast genomes are conservative and play an essential role in population diversity analysis. However, there are few studies on the chloroplast genome of R. japonica. In this study, the complete chloroplast genomes of three R. japonica from different regions were performed by next-generation sequencing technology. The results revealed that the lengths of the three chloroplast genomes are between 163,371~163,372 bp, and they have a highly conserved structure with a pair of inverted repeat (IR) regions (31,121 bp), a large single-copy (LSC) region (87,571~87,572 bp), and a small single-copy (SSC) region (13,558 bp). In total, 132 genes were annotated, including 8 rRNA genes, 37 tRNA genes, and 87 protein-coding genes. The phylogenetic analysis strongly revealed that 13 populations of R. japonica form a monophyly, and Fallopia multiflora (Polygonaceae) is its closest species. The two species diverged at ~20.47 million years ago, and R. japonica in China could be further divided into two major groups based on genetic structure analysis. In addition, several potential loci with suitable polymorphism were identified as molecular markers. Our study provides important genetic resources for further development and utilization of R. japonica germplasm, as well as some new insights into the evolutionary characteristics of this medicinal plant. [ABSTRACT FROM AUTHOR]

The pollution of soil with heavy metals (HMs) has become an environmental problem of global concern. Phytoremediation, whereby plants extract HMs from soil, can efficiently and substantially reduce HM pollution in soil in an environmentally friendly manner. Cadmium-induced protein AS8 (CIPAS8) is present in many plants and its expression is induced by HMs. In this study, PeCIPAS8 and SlCIPAS8 were transformed into 84K poplar to study their effects on tolerance to, and translocation of, cadmium (Cd) in woody plants. Localization analyses showed that two CIPAS8 proteins were localized at the plasma membrane when transiently expressed in tobacco leaf epidermal cells. Compared with wild-type 84K poplar seedlings, transgenic poplar lines overexpressing PeCIPAS8 or SlCIPAS8 showed increased Cd contents and decreased Cd tolerance. Transgenic poplar lines overexpressing PeCIPAS8 or SlCIPAS8 accumulated more Cd in the roots, stems, and leaves, but the plant height did not differ significantly, compared with wild-type 84K poplar under Cd stress during the vegetative stage. CIPAS8 increased the Cd influx rate of transgenic poplar roots compared with that of the wild type, and affected the transcription levels of other metal transporters. These findings show that CIPAS8 increases Cd flux into plant tissues and demonstrate moderate Cd sensitivity of the plant. Therefore, CIPAS8 is an influx transporter with the potential to increase the uptake of toxic HMs by woody plants growing in HM-contaminated soils. [Display omitted] • PeCIPAS8 and SlCIPAS8 are plasma membrane proteins. • CIPAS8 -OE/X poplar showed increased Cd content and Cd hypersensitivity. • Compared with wild type, CIPAS8 -OE/X accumulated more Cd in roots, stems, and leaves. • CIPAS8 may be Cd influx transporter for Cd removal in contaminated soil. [ABSTRACT FROM AUTHOR]

Excessive heavy metal contaminants in soils have serious ecological and environmental impacts, and affect plant growth and crop yields. Phytoremediation is an environmentally friendly means of lowering heavy metal concentrations in soils. In this study, we analyzed phenotypic and physiological traits, and the transcriptome and metabolome, of sheepgrass (Leymus chinensis) exposed to cadmium (Cd), lead (Pb), or zinc (Zn). Phenotypic and physiological analysis indicated that sheepgrass had strong tolerance to Cd/Pb/Zn. Transcriptomic analysis revealed that phenylpropanoid biosynthesis and organic acid metabolism were enriched among differentially expressed genes, and metabolomic analysis indicated that the citrate cycle was enriched in response to Cd/Pb/Zn exposure. Genes encoding enzymes involved in the phenylpropanoid and citrate cycle pathways were up-regulated under the Cd/Pb/Zn treatments. Organic acids significantly reduced heavy metal accumulation and improved sheepgrass tolerance of heavy metals. The results suggest that synergistic interaction of the phenylpropanoid and citrate cycle pathways in sheepgrass roots induced organic acid secretion to alleviate heavy metal toxicity. A cascade of enzymes involved in the interacting pathways could be targeted in molecular design breeding to enhance phytoremediation. [Display omitted] • Sheepgrass as the edificator grassland species had strong Cd, Pb, and Zn tolerance. • Synergy of phenylpropanoid and TCA cycle can secrete large amounts of organic acids. • Excessive secretion of organic acids alleviate the toxicity of Cd/Pb/Zn. • Phenylpropanoid and TCA cycle enzymes had up-regulated expression under heavy metal. • Organic acids enhance heavy metal tolerance through inhibition of ion uptake. [ABSTRACT FROM AUTHOR]

Background and Aims Ribonucleotide reductase (RNR), functioning in the de novo synthesis of deoxyribonucleoside triphosphates (dNTPs), is crucial for DNA replication and cell cycle progression. In most plants, the large subunits of RNR have more than one homologous gene. However, the different functions of these homologous genes in plant development remain unknown. In this study, we obtained the mutants of two large subunits of RNR in tomato and studied their functions. Methods The mutant ylc1 was obtained by ethyl methyl sulfonate (EMS) treatment. Through map-based cloning, complementation and knock-out experiments, it was confirmed that YLC1 encodes a large subunit of RNR (SlRNRL1). The expression level of the genes related to cell cycle progression, chloroplast biogenesis and photosynthesis was assessed by RNA-sequencing. In addition, we knocked out SlRNRL2 (a SlRNRL1 homologue) using CRISPR-Cas9 technology in the tomato genome, and we down-regulated SlRNRL2 expression in the genetic background of slrnrl1-1 using a tobacco rattle virus-induced gene silencing (VIGS) system. Key results The mutant slrnrl1 exhibited dwarf stature, chlorotic young leaves and smaller fruits. Physiological and transcriptomic analyses indicated that SlRNRL1 plays a crucial role in the regulation of cell cycle progression, chloroplast biogenesis and photosynthesis in tomato. The slrnrl2 mutant did not exhibit any visible phenotype. SlRNRL2 has a redundant function with SlRNRL1, and the double mutant slrnrl1slrnrl2 is lethal. Conclusions SlRNRL1 is essential for cell cycle progression, chloroplast biogenesis and photosynthesis. In addition, SlRNRL1 and SlRNRL2 possess redundant functions and at least one of these RNRLs is required for tomato survival, growth and development. [ABSTRACT FROM AUTHOR]

Abstract: Manganese (Mn) can interact with cadmium (Cd) in environments and influence the toxic effect of Cd on plants. However, few studies have investigated the relationship between the Mn/Cd ratio and plant Cd-toxicity along Cd concentrations. In this paper, we studied the effects of external Mn/Cd molar ratios (0, 10, 30, 50 and 60) on Cd toxicity in the Mn hyperaccumulator and Cd tolerant plant, Phytolacca acinosa Roxb., at three Cd levels (50, 100 and 200 μM) under hydroponic conditions. Our result showed that seedling growth (y) under Cd stress was strongly positively related to the solution Mn/Cd molar ratio (SMCR). The relationship between the two variables under solution Cd concentrations was well explained by the linear regression model y = a + b1 (SMCR) + b2 (Solution-Cd). Increasing SMCR significantly reduced the Cd concentration and increased the Mn concentration in plant tissues. However, seedling growth was consistent with the shoot Mn/Cd molar ratio rather than with the Mn or Cd concentrations in plant tissues. At low levels of SMCR (e.g. 0 and 10), elevation of Mn distribution in shoot tissues might be a mechanism in P. acinosa seedlings to defend against Cd-toxicity. In comparison with low levels of SMCR, high levels of SMCR (e.g. 50 and 60) greatly alleviated lipid peroxidation and plant water-loss, and enhanced photosynthesis. However, the alleviated lipid peroxidation in the Mn-mitigation of Cd toxicity was likely to be the secondary effect resulting from the antagonism between Mn and Cd in the plant. [Copyright &y& Elsevier]

Currently, there are few studies concerning the function of heavy metal ATPase 2 ( HMA2), particularly in monocotyledons, and the potential application of this protein in biofortification and phytoremediation. Thus, we isolated and characterized the Ta HMA2 gene from wheat ( Triticum aestivum L.). Our results indicate that Ta HMA2 is localized to the plasma membrane and stably expressed, except in the nodes, which showed relatively high expression. Zinc/cadmium ( Zn/ Cd) resistance was observed in Ta HMA2-transformed yeast. The over-expression of Ta HMA2 increased the elongation and decreased the seed-setting rate in rice ( Oryza sativa L.), but not Arabidopsis thaliana, tobacco ( Nicotiana tabacum L.) or wheat. Ta HMA2 over-expression also improved root-shoot Zn/ Cd translocation, especially in rice. The seeds of transgenic rice and wheat, not tobacco, showed decreased Zn concentrations. The Zn concentration was decreased in all parts of the transgenic rice seeds, but was decreased only in the ventral endosperm of wheat, which showed an increased Zn concentration in the embryo and aleurone. The over-expression of Ta HMA2 improved plant tolerance under moderate Zn stress and Zn deficiency, but Zn and Cd resistance decreased under high levels of Zn and Cd stress, respectively. The Cd concentration in transgenic rice seedlings was dramatically increased under Zn deficiency. Thus, over-expression of Ta HMA2 showed a more obvious phenotype in monocotyledons than in dicotyledons. These findings provide important information for Ta HMA2, and more efforts should be made in the future to characterize the reduced Zn concentration in Ta HMA2 transgenic grains and the diversity of Ta HMA2 substrate specificity. [ABSTRACT FROM AUTHOR]

Abstract: Synchrotron radiation X-ray fluorescence (SRXRF) and inductively coupled plasma mass spectrometry were used to estimate major, minor and trace elements in Cu-, Zn- and Mn-treated Phytolacca americana. The effects of the addition of Cu, Zn and Mn on morphological parameters, such as root length, shoot height, and fresh and dry weights of shoots and roots, were also examined. In addition, the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases (GPX) and catalase (CAT) and the expression of Fe-SOD, Cu/Zn-SOD, metallothionein-2 and glutathione S-transferase (GST) exposed to the highest amounts of Cu, Zn or Mn were detected. Our results confirmed the following: (1) Zn supplementation leads to chlorosis, disturbed elemental homeostasis and decreased concentrations of micro- and macroelements such as Fe, Mg, Mn, Ca and K. Cu competed with Fe, Mn and Zn uptake in plants supplemented with 25μM Cu. However, no antagonistic interactions took place between Cu, Zn, Mn and Fe uptake in plants supplemented with 100μM Cu. Mn supplementation at various concentrations had no negative effects on elemental deficits. Mn was co-located with high concentrations of Fe and Zn in mature leaves and the concentrations of macro elements were unchanged. (2) P. americana supplemented with increased concentrations of Zn and Cu exhibited lower biomass production and reduced plant growth. (3) When plants were supplemented with the highest Zn and Cu concentrations, symptoms of toxicity corresponded to decreased SOD or CAT activities and increased APX and GPX activities. However, Mn tolerance corresponded to increased SOD and CAT activities and decreased POD and APX activities. Our study revealed that heavy metals partially exert toxicity by disturbing the nutrient balance and modifying enzyme activities that induce damage in plants. However, P. americana has evolved hyper accumulating mechanisms to maintain elemental balance and redox homeostasis under excess Mn. [Copyright &y& Elsevier]

Mineral nutrients, such as manganese (Mn) and iron (Fe), play essential roles in many biological processes in plants but their over-enrichment is harmful for the metabolism. Metal tolerance proteins (MTPs) are involved in cellular Mn and Fe homeostasis. However, the transporter responsible for the transport of Mn in wheat is unknown. In our study, TuMTP8, a Mn-CDF transporter from diploid wheat (Triticum urartu), was identified. Expression of TuMTP8 in yeast strains of Δccc1 and Δsmf1 and Arabidopsis conferred tolerance to elevated Mn and Fe, but not to other metals (zinc, cobalt, copper, nickel, or cadmium). Compared with TuVIT1 (vacuole Fe transporter), TuMTP8 shows a significantly higher proportion in Mn transport and a smaller proportion in Fe transport. The transient analysis in tobacco epidermal cells revealed that TuMTP8 localizes to vacuolar membrane. The highest transcript levels of TuMTP8 were in the sheath of the oldest leaf and the awn, suggesting that TuMTP8 sequesters excess Mn into the vacuole in these organs, away from more sensitive tissues. These findings indicate that TuMTP8, a tonoplast-localized Mn/Fe transporter, functions as a primary balancer to regulate Mn distribution in T. urartu under elevated Mn conditions and participates in the intracellular transport and storage of excess Mn as a detoxification mechanism, thereby conferring Mn tolerance. [ABSTRACT FROM AUTHOR]

Being an invasive plant, Polygonum cuspidatum is highly resilient and can survive in unfavorable environments for long periods; however, its molecular mechanisms associated with such environmental resistance are largely unknown. In this study, a WRKY transcription factor (TF) gene, PcWRKY11, was identified from P. cuspidatum by analyzing methyl jasmonate (MeJA)-treated transcriptome data. It showed a high degree of homology with WRKY11 from Arabidopsis thaliana, containing a WRKY domain and a zinc finger structure and II-d WRKY characteristic domains of HARF, a calmodulin-binding domain (C-motif), and a putative nuclear localization signal (NLS) through sequence alignment and functional element mining. qPCR analysis showed that the expression of PcWRKY11 can be induced by NaCl, osmotic stress, and UV-C. In this study, we also found that overexpression of PcWRKY11 in A. thaliana could significantly increase salt tolerance. To explore its possible molecular mechanism, further investigations showed that compared with the wild type (WT), under salt stress, the transgenic plants showed a lower malondialdehyde (MDA) content, higher expression of ascorbate peroxidase (APX) and superoxide dismutase (SOD), and higher enzyme activity of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Moreover, the transgenic plants also showed higher expression of Δ1-pyrroline-5-carboxylate synthase (AtP5CS), and higher contents of proline and soluble sugar. Taken together, these results indicate that PcWRKY11 may have a positive role in plants' adaptation to salinity conditions by reducing reactive oxygen species (ROS) levels and increasing osmosis substance synthesis. [ABSTRACT FROM AUTHOR]

A comparative transcriptomic and metabolomic analysis of Polygonum cuspidatum leaves treated with MeJA was carried out to investigate the regulatory mechanisms of its active compounds. A total of 692 metabolites and 77,198 unigenes were obtained, including 200 differentially accumulated metabolites and 6819 differentially expressed genes. We screened potential regulatory transcription factors involved in resveratrol and flavonoids biosynthesis, and successfully identified an MYB transcription factor, PcMYB62, which could significantly decrease the resveratrol content in P. cuspidatum leaves when over-expressed. PcMYB62 could directly bind to the MBS motifs in the promoter region of stilbene synthase (PcSTS) gene and repress its expression. Besides, PcMYB62 could also repress PcSTS expression and resveratrol biosynthesis in transgenic Arabidopsis thaliana. Our results provide abundant candidate genes for further investigation, and the new finding of the inhibitory role of PcMYB62 on the resveratrol biosynthesis could also potentially be used in metabolic engineering of resveratrol in P. cuspidatum. [ABSTRACT FROM AUTHOR]

Background: Polygonum cuspidatum Sieb. et Zucc. is a well-known medicinal plant whose pharmacological effects derive mainly from its stilbenes, anthraquinones, and flavonoids. These compounds accumulate differentially in the root, stem, and leaf; however, the molecular basis of such tissue-specific accumulation remains poorly understood. Because tissue-specific accumulation of compounds is usually associated with tissue-specific expression of the related biosynthetic enzyme genes and regulators, we aimed to clarify and compare the transcripts expressed in different tissues of P. cuspidatum in this study. Results: High-throughput RNA sequencing was performed using three different tissues (the leaf, stem, and root) of P. cuspidatum. In total, 80,981 unigenes were obtained, of which 40,729 were annotated, and 21,235 differentially expressed genes were identified. Fifty-four candidate synthetase genes and 12 transcription factors associated with stilbene, flavonoid, and anthraquinone biosynthetic pathways were identified, and their expression levels in the three different tissues were analyzed. Phylogenetic analysis of polyketide synthase gene families revealed two novel CHS genes in P. cuspidatum. Most phenylpropanoid pathway genes were predominantly expressed in the root and stem, while methylerythritol 4-phosphate and isochorismate pathways for anthraquinone biosynthesis were dominant in the leaf. The expression patterns of synthase genes were almost in accordance with metabolite profiling in different tissues of P. cuspidatum as measured by high-performance liquid chromatography or ultraviolet spectrophotometry. All predicted transcription factors associated with regulation of the phenylpropanoid pathway were expressed at lower levels in the stem than in the leaf and root, but no consistent trend in their expression was observed between the leaf and the root. Conclusions: The molecular knowledge of key genes involved in the biosynthesis of P. cuspidatum stilbenes, flavonoids, and anthraquinones is poor. This study offers some novel insights into the biosynthetic regulation of bioactive compounds in different P. cuspidatum tissues and provides valuable resources for the potential metabolic engineering of this important medicinal plant. [ABSTRACT FROM AUTHOR]

Plant anthranoids are medicinally used for their purgative properties. Their scaffold was believed to be formed by octaketide synthase (OKS), a member of the superfamily of type III polyketide synthase (PKS) enzymes. Here, a cDNA encoding OKS of Polygonum cuspidatum was isolated using a homology-based cloning strategy. When produced in Escherichia coli , P. cuspidatum octaketide synthase (PcOKS) catalyzed the condensation of eight molecules of malonyl-CoA to yield a mixture of unphysiologically folded aromatic octaketides. However, when the ORF for PcOKS was expressed in Arabidopsis thaliana , the anthranoid emodin was detected in the roots of transgenic lines. No emodin was found in the roots of wild-type A. thaliana. This result indicated that OKS is the key enzyme of plant anthranoids biosynthesis. In addition, the root growth of the transgenic A. thaliana lines was inhibited to an extent that resembled the inhibitory effect of exogenous emodin on the root growth of wild-type A. thaliana. Immunochemical studies of P. cuspidatum plants detected PcOKS mainly in roots and rhizome, in which anthranoids accumulate. Co-incubation of E. coli - produced PcOKS and cell-free extract of wild-type A. thaliana roots did not form a new product, suggesting an alternative, physiological folding of PcOKS and its possible interaction with additional factors needed for anthranoids assembling in transgenic A. thaliana. Thus, transgenic A. thaliana plants producing PcOKS provide an interesting system for elucidating the route of plant anthranoid biosynthesis. [ABSTRACT FROM AUTHOR]

Background: Polygonum cuspidatum of the Polygonaceae family is a traditional medicinal plant with many bioactive compounds that play important roles in human health and stress responses. Research has attempted to identify biosynthesis genes and metabolic pathways in this species, and quantitative real-time PCR (RT-qPCR) has commonly been used to detect gene expression because of its speed, sensitivity, and specificity. However, no P. cuspidatum reference genes have been identified, which hinders gene expression studies. Here, we aimed to identify suitable reference genes for accurate and reliable normalization of P. cuspidatum RT-qPCR data. Results: Twelve candidate reference genes, including nine common (ACT, TUA, TUB, GAPDH, EF-1γ, UBQ, UBC, 60SrRNA, and eIF6A) and three novel (SKD1, YLS8, and NDUFA13), were analyzed in different tissues (root, stem, and leaf) without treatment and in leaves under abiotic stresses (salt, ultraviolet [UV], cold, heat, and drought) and hormone stimuli (abscisic acid [ABA], ethylene [ETH], gibberellin [GA3], methyl jasmonate [MeJA], and salicylic acid [SA]). Expression stability in 65 samples was calculated using the △CT method, geNorm, NormFinder, BestKeeper, and RefFinder. Two reference genes (NDUFA13 and EF-1γ) were sufficient to normalize gene expression across all sample sets. They were also the two most stable genes for abiotic stresses and different tissues, whereas NDUFA13 and SKD1 were the top two choices for hormone stimuli. Considering individual experimental sets, GAPDH was the top-ranked gene under ABA, ETH, and GA3 treatments, while 60SrRNA showed good stability under MeJA and cold treatments. ACT, UBC, and TUB were suitable genes for drought, UV, and ABA treatments, respectively. TUA was not suitable because of its considerable variation in expression under different conditions. The expression patterns of PcPAL, PcSTS, and PcMYB4 under UV and SA treatments and in different tissues normalized by stable and unstable reference genes demonstrated the suitability of the optimal reference genes. Conclusions: We propose NDUFA13 and EF-1γ as reference genes to normalize P. cuspidatum expression data. To our knowledge, this is the first systematic study of reference genes in P. cuspidatum which could help advance molecular biology research in P. cuspidatum and allied species. [ABSTRACT FROM AUTHOR]

• Pro, H 2 O 2 , and GSH contents in the roots treated with Cd were significantly higher. • The secretions were deposited on the surface of root under Cd treatment. • WS and WR were located close to C2S and C2R, and distantly from the C5S and C5R. • "DNA replication" was the in-common pathway in WS vs. C5S and C2S vs. C5S. • Cd toxicity on the roots of T. urartu was related to "phenylpropanoid biosynthesis". Cadmium (Cd) is a widespread soil contaminant that readily accumulates in wheat, and posing a potential threat to human health. Our aim is to investigate Cd toxicity effect and molecular mechanisms for wheat. In this study, the physiological indexes, morphology, and gene expression patterns of diploid wheat (Triticum urartu) seedlings were evaluated after 2 and 5 d of a Cd treatment (10 μM CdSO 4). The Cd treatment resulted in increased proline and glutathione contents in shoots and roots, slight damage to leaf tips, severe damage to root tips, and increased root secretions. Transcriptome analysis showed that there were significantly more differentially expressed genes (DEGs) in shoots and roots after 5 d of Cd stress than after 2 d of Cd stress, and the DEGs of the shoots were more different than the roots. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the pathways enriched under Cd treatment were "DNA replication" and "phenylpropanoid biosynthesis". These findings provide information about the responses to Cd stress in wheat, and provide a theoretical basis for reducing Cd toxicity and protecting food safety. [ABSTRACT FROM AUTHOR]

Key message: TuCAX1a and TuCAX1b improved Ca2+ and Zn2+ translocation and TuCAX1b enhanced Ca2+, Zn2+, Mn2+ and Fe2+ content when exposed to Cd2+; Cd2+ translocation was inhibited under Ca2+ and Zn2+. Cation/H+ antiporters (CAXs) are involved in the translocation of Ca2+ and various metal ions in higher plants. In the present study, TuCAX1a and TuCAX1b, two cation/H+ antiporters, were isolated from the diploid wheat Triticum urartu, and their metal cation translocation functions investigated. TuCAX1a and TuCAX1b showed abundant tissue-specific expression in the internode and beard, respectively, and their expression levels were increased in shoots exposed to Cd2+, Zn2+ and Ca2+. Plant phenotype analysis showed that overexpression of TuCAX1a and TuCAX1b could improve the tolerance of Arabidopsis to exogenous Ca2+ and Zn2+. In the plant shoots and roots, the contents of Ca2+ and Zn2+ were higher than wild-type plants under Ca2+ and Zn2+ treatments, indicating that TuCAX1a and TuCAX1b can enhance Ca2+ and Zn2+ translocation. Ca2+, Zn2+, Mn2+ and Fe2+ contents showed higher accumulation in TuCAX1b-transgenic Arabidopsis shoots than in wild-type plants exposed to Cd2+, and the translocation of Cd2+ was inhibited under Ca2+ and Zn2+. Overall, the present study provides a novel genetic resource for improving the uptake of microelements and reducing accumulation of toxic heavy metals in wheat. [ABSTRACT FROM AUTHOR]

Summary: Grain size and weight are directly associated with grain yield in crops. However, the molecular mechanisms that set final grain size and weight remain largely unknown. Here, we characterize two large grain mutants, large grain8‐1 (large8‐1) and large grain8‐2 (large8‐2). LARGE8 encodes the mitogen‐activated protein kinase phosphatase1 (OsMKP1). Loss of function mutations in OsMKP1 results in large grains, while overexpression of OsMKP1 leads to small grains. OsMKP1 determines grain size by restricting cell proliferation in grain hulls. OsMKP1 directly interacts with and deactivates the mitogen‐activated protein kinase 6 (OsMAPK6). Taken together, we identify OsMKP1 as a crucial factor that influences grain size by deactivating OsMAPK6, indicating that the reversible phosphorylation of OsMAPK6 plays important roles in determining grain size in rice. [ABSTRACT FROM AUTHOR]

Key message: Cysteine in the N-terminal metal-binding domain (N-MBD) of TaHMA2 participates in Zn2+/Cd2+ binding and translocation in Arabidopsis.Abstract: Wheat heavy metal ATPase 2 (TaHMA2) can transport Zn2+ and Cd2+ across membranes. A previous study showed that cysteine (Cys) and glutamate residues in the N-terminal metal-binding domain (N-MBD) were necessary for metal-binding and translocation of TaHMA2 in yeast. However, the function of TaHMA2 in plants was not fully revealed. In this study, we investigated the roles of the CCxxE and CPC motifs in the N-MBD and the N/C-terminal regions of TaHMA2 in Zn2+/Cd2+ translocation in root and shoot of Arabidopsis. Compared with the wild type, overexpression of TaHMA2 and the TaHMA2 derivative (glutamic substituted for alanine from CCxxE) in Arabidopsis increased root length, fresh weight and enhanced Zn2+/Cd2+ root-to-shoot translocation. The plants with a truncated N/C-terminal of TaHMA2 were impaired in Zn2+/Cd2+ tolerance and translocation, while mutagenesis of Cys in the N-MBD reduced the tolerance and transport activity of TaHMA2, suggesting the involvement of Cys in Zn2+/Cd2+ binding and translocation in Arabidopsis. This study therefore provides a theoretical possibility for the application of TaHMA2 in transgenic breeding to regulate metal element balance in crop plants. [ABSTRACT FROM AUTHOR]

Key message: PcWRKY33 is a transcription factor which can reduce salt tolerance by decreasing the expression of stress-related genes and increasing the cellular levels of reactive oxygen species (ROS).Abstract: WRKY transcription factors play important roles in the regulation of biotic and abiotic stresses. Here, we report a group I WRKY gene from Polygonum cuspidatum, PcWRKY33, that encodes a nucleoprotein, which specifically binds to the W-box in the promoter of target genes to regulate their expression. The results from qPCR and promoter analysis show that expression of PcWRKY33 can be induced by various abiotic stresses, including NaCl and plant hormones. Overexpression of PcWRKY33 in Arabidopsis thaliana reduced tolerance to salt stress. More specifically, several physiological parameters (such as root length, seed germination rate, seedling survival rate, and chlorophyll concentration) of the transgenic lines were significantly lower than those of the wild type under salt stress. In addition, following exposure to salt stress, transgenic plants showed decreased expression of stress-related genes, a weakened ability to maintain Na+/K+ homeostasis, decreased activities of reactive oxygen species- (ROS-) scavenging enzymes, and increased accumulation of ROS. Taken together, these results suggest that PcWRKY33 negatively regulates the salt tolerance in at least two ways: by down-regulating the induction of stress-related genes and by increasing the level of cellular ROS. In sum, our results indicate that PcWRKY33 is a group I WRKY transcription factor involved in abiotic stress regulation. [ABSTRACT FROM AUTHOR]

Grain size is one of the key agronomic traits that determine grain yield in crops. However, the mechanisms underlying grain size control in crops remain elusive. Here we demonstrate that the OsMKKK10-OsMKK4-OsMAPK6 signaling pathway positively regulates grain size and weight in rice. In rice, loss of OsMKKK10 function results in small and light grains, short panicles, and semi-dwarf plants, while overexpression of constitutively active OsMKKK10 (CA-OsMKKK10) results in large and heavy grains, long panicles, and tall plants. OsMKKK10 interacts with and phosphorylates OsMKK4. We identified an OsMKK4 gain-of-function mutant ( large11-1D ) that produces large and heavy grains. OsMKK4 A227T encoded by the large11-1D allele has stronger kinase activity than OsMKK4. Plants overexpressing a constitutively active form of OsMKK4 (OsMKK4-DD) also produce large grains. Further biochemical and genetic analyses revealed that OsMKKK10, OsMKK4, and OsMAPK6 function in a common pathway to control grain size. Taken together, our study establishes an important genetic and molecular framework for OsMKKK10-OsMKK4-OsMAPK6 cascade-mediated control of grain size and weight in rice. [ABSTRACT FROM AUTHOR]

Toxic heavy metals originating from human activities have caused irreversible harm to the environment. Toxic heavy metal ions absorbed by crop plants can seriously threaten human health. Therefore, decreasing heavy metal contents in crop plants is an urgent need. The plant cadmium resistance protein (PCR) is a heavy metal ion transporter. In this study, PePCR10 was cloned from Populus euphratica. Bioinformatics analyses revealed its transmembrane structure and gene sequence motifs. The transcript profile of PePCR10 was analyzed by RT-qPCR, and its transcript levels increased under toxic heavy metal (cadmium, lead, aluminum) treatments. Subcellular localization analyses in tobacco cells revealed that PePCR10 localizes at the plasma membrane. Compared with wild type (WT), PePCR10 -overexpressing lines showed significantly higher values for plant height, root length, fresh weight, and dry weight under heavy metal stress. Electrolyte leakage, nitroblue tetrazolium staining, and chlorophyll fluorescence analyses indicated that Cd/Al tolerance in PePCR10 -overexpressing lines was stronger than that in WT. The Cd/Al contents were lower in the PePCR10 -overexpressing lines than in WT under Cd/Al stress. Our results show that PePCR10 can reduce the heavy metal content in poplar and enhance its Cd/Al tolerance. Hence, PePCR10 is a candidate genetic resource for effectively reducing heavy metal accumulation in crops. [Display omitted] • PePCR10 was confirmed to be a plasma membrane-localized protein. • PePCR10 enhanced Cd/Al tolerance by promoting Cd/Al efflux in poplar. • PePCR10 can be used to reduce the risks of heavy metals to humans. [ABSTRACT FROM AUTHOR]

Soil bacteria play a vital role in terrestrial ecosystems and are very sensitive to changes in the environment. Land subsidence due to underground coal mining could affect soil properties, but the extent of this effect on the soil bacterial community remains unclear. Here, we investigated the effect of land subsidence on soil bacterial communities and their response to changes in the soil environment in a control area and a land subsidence area in the West China Aeolian Sand Area. The results showed that electrical conductivity (EC), total carbon, (TC), total nitrogen (TN), available potassium (AK) and soil organic matter (SOM) at a soil depth of 20 cm were significantly decreased in the land subsidence area compared to the unexploited area, and Illumina MiSeq sequencing data revealed that the bacterial community at a soil depth of 0–180 cm was dominated by Pseudomonas, Gp4, Gp6, Sphingomonas , Gemmatimonas, Arthrobacter , Aciditerrimonas and Gaiella . Land subsidence decreased soil microbial richness and diversity. In addition, there was a significant decrease in the relative abundance of some core genera in the topsoil, such as Sphingomonas, Nocardioides and Saccharibacteria_genera_incertae_sedis , indicating that the dominant bacteria had strong anti-interference abilities and played important roles in the nutrient-poor soils of the mining area. Redundancy analysis (RDA) showed that the main factors driving the changes in the bacterial community structure were EC, water content (WC) and soil depth. The vertical leakage of water and nutrients was caused by subsidence and cracks in the ground, leading to decreased soil microbial richness and diversity. These results suggested that the soil nutrients and soil microbial community has yet to recover by self-healing after two years of land subsidence; thus, artificial restoration might be required. [ABSTRACT FROM AUTHOR]

Key message : SnYSL3 encodes a plasma-localized transporter delivering various metal-nicotianamine complexes. The expression of SnYSL3 is up-regulated by excess Cd, suggesting an important role for SnYSL3 in response to Cd stress. Abstract: The Yellow Stripe-Like (YSL) transporters have been proposed to participate in metal uptake and long-range transport in model plants. In this study, we isolated and characterized a novel member of the YSL gene family, SnYSL3, from the cadmium hyperaccumulator Solanum nigrum. SnYSL3 was constitutively expressed and encodes a plasma membrane-localized protein. In situ RNA hybridization localized the SnYSL3 transcripts predominantly in vascular tissues and epidermal cells of the roots and stems, while in leaves, the mRNA levels were high in the vasculature. The SnYSL3 expression level was up-regulated by excess Cd, excess Fe and Cu deficiency. Heterologous expression of SnYSL3 in yeast revealed that SnYSL3 transports nicotianamine complexes containing Fe(II), Cu, Zn and Cd. SnYSL3 overexpression in Arabidopsis thaliana decreased Fe and Mn concentrations in the roots and increased the root-to-shoot translocation ratios of Fe and Mn. Under Cd exposure, the transgenic plants showed increased translocation ratios of Fe and Cd, but no difference was observed in Mn translocation from roots to shoots between the transgenic and wild-type lines. Although the accurate function of SnYSL3 remains to be confirmed, these results suggest that SnYSL3 is a transporter delivering a broad range of metal-nicotianamine complexes and is potentially important for the response to heavy metal stress, especially due to Cd and Fe. [ABSTRACT FROM AUTHOR]

Quinoline is a refractory organic compound in the treatment of coking wastewater. The isolation of high efficiency quinoline-degrading bacteria from activated sludge and the evaluation of their degradation characteristics in the presence of phenol or in the actual coking wastewater are important for the improvement of effluent quality. The novel bacterial strainPseudomonas aeruginosaKDQ4 was isolated from a quinoline enrichment culture obtained from the activated sludge of a coking wastewater treatment plant. The optimum temperature and initial pH for quinoline degradation were 33–38°C and 8–9, respectively. KDQ4 completely degraded 400 mg/L of quinoline within 24 h and 800 mg/L of phenol within 30 h. In the dual-substrate system, the removal efficiencies of quinoline and phenol at the same initial concentration (200 mg/L) by KDQ4 were 89% and 100% within 24 h, respectively, indicating that KDQ4 could simultaneously and quickly degrade quinoline and phenol in a coexistence system. Moreover, KDQ4 was able to adapt to actual coking wastewater containing high quinoline and phenol concentrations and rapidly remove them. KDQ4 also exhibited heterotrophic nitrification and aerobic denitrification potential under aerobic conditions. These results suggested a potential bioaugmentation role for KDQ4 in the removal of nitrogen-heterocyclic compounds and phenolics from coking wastewater. [ABSTRACT FROM AUTHOR]

Key message: We identified key residues of TaHMA2, and the N- and C-terminal regions of the protein have different roles in its transport function when heterologously expressed in yeast. Abstract: TaHMA2, a P-type ATPase from wheat ( Triticum aestivum L.), plays an important role in heavy metal homeostasis in plants. A previous study showed that overexpressing TaHMA2 in rice ( Oryza sativa L.), Arabidopsis thaliana, or tobacco ( Nicotiana tabacum L.) resulted in various responses to heavy metals. Here, we report the heterologous expression of TaHMA2 in the yeast Saccharomyces cerevisiae. TaHMA2 expression increased the yeast's sensitivity to Cd, but not to Zn, Pb or Co, and increased Cd accumulation was concurrently observed. The eGFP-TaHMA2 fusion protein was localized to the plasma membrane and showed a discontinuous pattern. Mutagenesis of the cysteine and glutamate residues in the N-terminal metal-binding domain (N-MBD) impaired the function of TaHMA2. Deletion of most of the C terminus (TaHMA2ΔC, 712-1003) partially abolished the protein's function, whereas deletion of the N terminus (TaHMA2ΔN, 2-699) completely abolished Cd sensitivity. These data suggest that cysteine and glutamate residues are important for the metal-binding/translocation function of TaHMA2. Additional studies are needed to further understand the selectivity of TaHMA2 in planta. [ABSTRACT FROM AUTHOR]

Abstract: Solanum nigrum L. is considered to be a potential plant for restoring Cd-contaminated soils. Si could enhance plants tolerance to heavy metal; however, the mechanism of Si-mediated alleviation of Cd toxicity in S. nigrum was not clear. Three-week-old S. nigrum seedlings were grown in Hoagland solution containing 0 or 100 μM Cd with or without 1 mM Si for 4 days. The results showed that the Cd concentration both in roots and shoots of Si-supplied plant was significantly reduced, especially in expanding and old leaves. The relative proportion of ethanol-extractable Cd, water-extractable Cd and NaCl-extractable Cd in roots was increased by adding Si, while the root-to-shoot Cd translocation was not decreased. Furthermore, in comparison with single Cd treatment, supplying Si could reduce H2O2 accumulation and cell death in roots, and the electrolyte leakage and H2O2 concentration in functional leaves. Moreover, the activity of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) in functional leaves was markedly increased by Cd exposure, while the antioxidative enzyme activities in Cd plus Si treatment seedlings were significantly lower than that in Cd treatment alone, this decrease might be attributed to the reduction of Cd concentration and Cd-induced oxidative damages. These results demonstrate that Si-enhanced Cd tolerance in S. nigrum is mainly due to the decrease of Cd uptake in roots and Cd distribution in expanding and old leaves, as well as lowering oxidative stress induced by Cd in plants. [Copyright &y& Elsevier]

Highlights: [•] Oxidative capability and mechanism of activated persulfate were investigated. [•] Thermal and chelated ferrous activated persulfate showed high removal of PAHs. [•] Thermal activation facilitated high molecular weight PAHs removal by persulfate. [•] Hydroxyl radicals in thermal activated systems contribute to high PAHs removal. [ABSTRACT FROM AUTHOR]

Summary: The stress-related gene no. 2 of Phaseolus vulgaris (PvSR2) is metal inducible and contains a single intron. Here, we report that Zn stress inhibited the splicing of the PvSR2–β-glucuronidase (GUS) fusion gene in a concentration- and time-dependent manner in tobacco seedlings. The inhibition appears to be specific for the PvSR2–GUS transgene: splicing of four endogenous tobacco genes was unaffected by Zn stress. Our results provide in vivo evidence that Zn stress-dependent intron retention is transgene specific in plants. [Copyright &y& Elsevier]

Dehydrins are capable of conferring abiotic stress tolerance in plants. Few dehydrins have been characterized at the molecular and transgenic level in Brassica juncea. In the present study, two SK2-type B. juncea dehydrin genes, BjDHN2 and BjDHN3, showed improved stress tolerance to salt and freezing stress in transgenic yeast. Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) revealed that BjDHN2 and BjDHN3 were up-regulated by low temperature, drought, and salt stress, as well as exogenous abscisic acid (ABA) in B. juncea. Transgenic studies also showed that BjDHN2 and BjDHN3 increased tolerance to cold and salt stress in tobacco. These results indicate that the BjDHN2 and BjDHN3 genes exert a protective role on membranes and play a role in abiotic stresses. [ABSTRACT FROM AUTHOR]

Heavy metals negatively affect soil quality and crop growth. In this study, we compared the tolerance of six ryegrass cultivars to cobalt (Co2+), lead (Pb2+), and nickel (Ni2+) stresses by analyzing their physiological indexes and transcript levels of genes encoding metal transporters. Compared with the other cultivars, the cultivar Lm1 showed higher germination rates and better growth under Co2+, Pb2+, or Ni2+ treatments. After 48 h of Co2+ treatment, the total antioxidant capacity of all six ryegrass cultivars was significantly increased, especially that of Lm1. In contrast, under Pb2+ stress, total antioxidant capacity of five cultivars was significantly decreased, but that of Lm1 was unaffected at 24 h. Staining with Evans blue dye showed that the roots of Lm1 were less injured than were roots of the other five ryegrass cultivars by Co2+, Pb2+, and Ni2+. Lm1 translocated and accumulated lesser Co2+, Pb2+, and Ni2+ than other cultivars. In Lm1, genes encoding heavy metal transporters were differentially expressed between the shoots and roots in response to Co2+, Pb2+, and Ni2+. The aim of these researches could help find potential resource for phytoremediation of heavy metal contamination soil. The identified genes related to resistance will be useful targets for molecular breeding. [ABSTRACT FROM AUTHOR]

• Node Ⅰ plays critical role in metal transportation. • OsLCT1, OsHMA2 and OsZIP3 are involved in cadmium and zinc distribution. • Transgene-Stacking II system helps to co-express three transporters efficiently. • Co-expression rice lines are low Cd accumulation plants. The OsHMA2, OsLCT1 and OsZIP3 transporters were all involved in zinc (Zn) and cadmium (Cd) transport. So far, only a few researches studied on the co- regulation effect of three transporters related to Zn and Cd transport. The present study showed that rice co- expressing OsLCT1 - OsHMA2 - OsZIP3 (LHZ) had longer roots and shoots than wild-type (WT) rice after Zn and Cd treatments. The chlorophyll content was significantly higher, and the proline, malondialdehyde and H 2 O 2 contents were significantly lower in co- transgenic lines than in WT under Cd and Zn stress. LHZ in the seedlings of transgenic rice decreased the root-to-shoot translocation of Cd after Cd and Zn treatments. At the filling stage, LHZ line reduced Cd accumulation in grain after Cd treatment. Moreover, LHZ line increased the translocation of Zn to grain and reduced the accumulation of Cd after Zn treatment. These results suggested that LHZ co-expression could effectively decrease the translocation and accumulation of Cd to grains, alleviated the oxidative stress of Cd and Zn, and finally enhanced the quality and safety of rice grains. [ABSTRACT FROM AUTHOR]

Polygonum cuspidatum Sieb. et Zucc. is a traditional Chinese herbal medicine widely used to treat tussis, hepatitis and arthralgia. This study identified and quantitatively described the bioactive compounds in different P. cuspidatum tissues. Metabolic profiles of root, stem, leaf, flower, rhizome and seed were determined using high-resolution mass spectrometry in combination with multivariate analyses. In total, 53 metabolites, 8 reported for the first time in this species, were putatively identified and classified mainly as stilbenes, anthraquinones and flavonoids. A principal component analysis, cluster analysis and heatmap were used to depict the correlations between specimens and the relative abundance levels of these compounds in different plant tissues. An orthogonal partial least square discriminant analysis found that 13 metabolites showed distinct differences among the six plant tissues, making them potential discriminative tissue-identification markers. This study will provide guidance in comparing, selecting and exploiting the medicinal uses of different P. cuspidatum tissues. [ABSTRACT FROM AUTHOR]

Background: HMA4 transporters are involved in the transport and binding of divalent heavy metals (Cd, Zn, Pb [lead] and Co [cobalt]). In general, as efflux pumps, HMA4 transporters can increase the heavy metal tolerance of yeast and Escherichia coli. Additional research has shown that the C-terminus of HMA4 contains a heavy metal-binding domain and that heterologous expression of a portion of peptides from this C-terminal domain in yeast provides a high level of Cd tolerance and Cd hyperaccumulation. Results: We cloned BjHMA4 from Brassica juncea, and quantitative real-time PCR analysis revealed that BjHMA4 was upregulated by Zn and Cd in the roots, stems and leaves. Overexpression of BjHMA4 dramatically affects Zn/Cd distribution in rice and wheat seedlings. Interestingly, BjHMA4 contains a repeat region named BjHMA4R within the C-terminal region; this repeat region is not far from the last transmembrane domain. We further characterized the detailed function of BjHMA4R via yeast and E. coli experiments. Notably, BjHMA4R greatly and specifically improved Cd tolerance, and BjHMA4R transformants both grew on solid media that contained 500 μM CdCl2 and presented improved Cd accumulation (approximately twice that of wild-type [WT] strains). Additionally, visualization via fluorescence microscopy indicated that BjHMA4R clearly localizes in the cytosol of yeast. Overall, these findings suggest that BjHMA4R specifically improves Cd tolerance and Cd accumulation in yeast by specifically binding Cd2+ in the cytosol under low heavy metal concentrations. Moreover, similar results in E. coli experiments corroborate this postulation. Conclusion: BjHMA4R can specifically bind Cd2+ in the cytosol, thereby substantially and specifically improving Cd tolerance and accumulation under low heavy metal concentrations. [ABSTRACT FROM AUTHOR]

Pyridine is a typical nitrogen heterocyclic and recalcitrant organic compound in coking wastewater. The pyridine-degrading bacterial strain KDPy1 was isolated from aerobic sludge in a coking wastewater treatment plant. The homology analysis based on 16S rDNA sequences suggested that KDPy1 belongs to Rhodococcus sp. The optimum temperature and pH for pyridine degradation by KDPy1 were 37°C and 7–8, respectively. The strain KDPy1 degraded 1442 mg/L of pyridine nearly 99.6% after 48 h, and the high concentration of 1442 mg/L pyridine did not show an inhibitory effect on its degradation. The degradation kinetics of pyridine were fitted with the Monod model. Furthermore, KDPy1 was capable of degrading pyridine efficiently in the synthetic wastewater containing quinoline and phenol. KDPy1 could degrade pyridine and reduce the total organic carbon in the real coking wastewater. These results showed that KDPy1 had a potential for improving the removal of pyridine from coking wastewater. [ABSTRACT FROM AUTHOR]