Self-Limiting Phase Transition Enabling Reversible Overstoichiometric Li Storage in Ni-Rich Cathodes.

Ni-rich cathodes are some of the most promising candidates for advanced lithium-ion batteries, but their available capacities have been stagnant due to the intrinsic Li+ storage sites. Extending the voltage window down can induce the phase transition from O3 to 1T of LiNiO2-derived cathodes to accommodate excess Li+ and dramatically increase the capacity. By setting the discharge cutoff voltage of LiNi0.6Co0.2Mn0.2O2 to 1.4 V, we can reach an extremely high capacity of 393 mAh g-1 and an energy density of 1070 Wh kg-1 here. However, the phase transition causes fast capacity decay and related structural evolution is rarely understood, hindering the utilization of this feature. We find that the overlithiated phase transition is self-limiting, which will transform into solid-solution reaction with cycling and make the cathode degradation slow down. This is attributed to the migration of abundant transition metal ions into lithium layers induced by the overlithiation, allowing the intercalation of overstoichiometric Li+ into the crystal without the O3 framework change. Based on this, the wide-potential cycling stability is further improved via a facile charge-discharge protocol. This work provides deep insight into the overstoichiometric Li+ storage behaviors in conventional layered cathodes and opens a new avenue toward high-energy batteries.

Chemical-Mechanical Robustness of Single-Crystalline Ni-Rich Cathode Enabled by Surface Atomic Arrangement Control.

Layered transition metal oxide cathodes have been one of the dominant cathodes for lithium-ion batteries with efficient Li+ intercalation chemistry. However, limited by the weak layered interaction and unstable surface, mechanical and chemical failure plagues their electrochemical performance, especially for Ni-rich cathodes. Here, adopting a simultaneous elemental-structural atomic arrangement control based on the intrinsic Ni-Co-Mn system, the surface role is intensively investigated. Within the invariant oxygen sublattice of the crystal, a robust surface with the synergistic concentration gradient and layered-spinel intertwined structure is constructed on the model single-crystalline Ni-rich cathode. With mechanical strain dissipation and chemical erosion suppression, the cathode exhibits an impressive capacity retention of 82 % even at the harsh 60 °C after 150 cycles at 1 C. This work highlights the coupling effect of structure and composition on the chemical-mechanical properties, and the concept will spur more researches on the cathodes that share the same sublattice.

Anatomy and RNA-Seq reveal important gene pathways regulating sex differentiation in a functionally Androdioecious tree, Tapiscia sinensis.

BACKGROUND: Gametogenesis is a key step in the production of ovules or pollen in higher plants. The sex-determination aspects of gametogenesis have been well characterized in the model plant Arabidopsis. However, little is known about this process in androdioecious plants. Tapiscia sinensis Oliv. is a functionally androdioecious tree, with both male and hermaphroditic individuals. Hermaphroditic flowers (HFs) are female-fertile flowers that can produce functional pollen and set fruits. However, compared with male flowers (MFs), the pollen viability and number of pollen grains per flower are markedly reduced in HFs. MFs are female-sterile flowers that fail to set fruit and that eventually drop. RESULTS: Compared with HF, a notable cause of MF female sterility in T. sinensis is when the early gynoecium meristem is disrupted. During the early stage of HF development (stage 6), the ring meristem begins to form as a ridge around the center of the flower. At this stage, the internal fourth-whorl organ is stem-like rather than carpelloid in MF. A total of 52,945 unigenes were identified as transcribed in MF and HF. A number of differentially expressed genes (DEGs) and metabolic pathways were detected as involved in the development of the gynoecium, especially the ovule, carpel and style. At the early gynoecium development stage, DEGs were shown to function in the metabolic pathways regulating ethylene biosynthesis and signal transduction (upstream regulator), auxin, cytokinin transport and signalling, and sex determination (or flower meristem identity). CONCLUSIONS: Pathways for the female sterility model were initially proposed to shed light on the molecular mechanisms of gynoecium development at early stages in T. sinensis.

[Trace Amounts of Phosphorus Removal Based on the in-suit Oxidation Products of Iron or Manganese in a Biofilter].

In order to remove trace amounts of phosphorus from water bodies, a lab-scale biofilter was constructed to investigate the capacity of in situ oxidation products of iron or manganese for phosphorus adsorption. SEM, EDS, BET, and zeta technologies were employed to reveal the adsorption mechanisms. The results indicated that phosphorus could be removed by the oxide products generated from the iron or manganese removal process, at 106.28 µg·mg-1 and 77.98 µg·mg-1, respectively, as shown by the linear relationships between phosphorus removal and the two oxides. SEM, EDS, and BET analysis demonstrated that the BET specific surface areas for the iron- and manganese-rich oxides were 96 m2·g-1 and 67 m2·g-1, respectively, with the former accumulated between the pore spaces of the filtering sand and easily washed out of the layer by backwashing, whereas the latter coated the surface of the filtering sand. Thus, backwashing was favorable for phosphorus adsorption in the iron oxidation process to avoid overaccumulation. Moreover, the zero point of charge of the two oxides indicated electrostatic attraction may have occurred between iron-rich oxide and phosphorus; however, inner-sphere complex reactions obviously occurred for the two oxides because the zero point of charge after phosphorus adsorption decreased to a lower level. In addition, other anions were negatively complexed with the phosphorus on the surface of the oxides, it demonstrated that phosphorus adsorption on the surface of the two oxides seemed to be a specific adsorption.

De novo transcriptomic analysis to identify differentially expressed genes during the process of aerenchyma formation in Typha angustifolia leaves.

Lysigenous aerenchyma is formed through programmed cell death (PCD) in Typha angustifolia leaves. However, the genome and transcriptome data for this species are unknown. To further elucidate the molecular basis of PCD during aerenchyma formation in T. angustifolia leaves, transcriptomic analysis of T. angustifolia leaves was performed using Illumina sequencing technology, revealing 73,821 unigenes that were produced by assembly of the reads in T1, T2 and T3 samples. The important pathways, such as programmed cell death (PCD), aerenchyma formation, and ethylene responsiveness were regulated by these unigenes. 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) were highly up-regulated as key enzymes for ethylene synthesis, along with respiratory burst oxidase homolog (RBOH), metallothionein, calmodulin-like protein (CML), and polygalacturonase (PG), may collectively explain the PCD involved in T. angustifolia aerenchyma formation. We hypothesize that fermentation, metabolism and glycolysis generate ATP for PCD. We searched the 73,821 unigenes against protein databases, and 24,712 were annotated. Based on sequence homology, 16,012 of the 73,821 annotated unigenes were assigned to one or more Gene Ontology (GO) terms. Meanwhile, a total of 9537 unigenes were assigned to 126 pathways in the KEGG database. In summary, this investigation provides important guidelines for exploring the molecular mechanisms of aerenchyma formation in aquatic plants.

Population genetics, phylogenomics and hybrid speciation of Juglans in China determined from whole chloroplast genomes, transcriptomes, and genotyping-by-sequencing (GBS).

Genomic data are a powerful tool for elucidating the processes involved in the evolution and divergence of species. The speciation and phylogenetic relationships among Chinese Juglans remain unclear. Here, we used results from phylogenomic and population genetic analyses, transcriptomics, Genotyping-By-Sequencing (GBS), and whole chloroplast genomes (Cp genome) data to infer processes of lineage formation among the five native Chinese species of the walnut genus (Juglans, Juglandaceae), a widespread, economically important group. We found that the processes of isolation generated diversity during glaciations, but that the recent range expansion of J. regia, probably from multiple refugia, led to hybrid formation both within and between sections of the genus. In southern China, human dispersal of J. regia brought it into contact with J. sigillata, which we determined to be an ecotype of J. regia that is now maintained as a landrace. In northern China, walnut hybridized with a distinct lineage of J. mandshurica to form J. hopeiensis, a controversial taxon (considered threatened) that our data indicate is a horticultural variety. Comparisons among whole chloroplast genomes and nuclear transcriptome analyses provided conflicting evidence for the timing of the divergence of Chinese Juglans taxa. J. cathayensis and J. mandshurica are poorly differentiated based our genomic data. Reconstruction of Juglans evolutionary history indicate that episodes of climatic variation over the past 4.5 to 33.80 million years, associated with glacial advances and retreats and population isolation, have shaped Chinese walnut demography and evolution, even in the presence of gene flow and introgression.

The involvement of programmed cell death in inflated leaf petiole morphogenesis in Trapa pseudoincisa.

Trapa plants (Trapaceae) have an inflated leaf petiole called a spongy airbag. The aims of this study were to assess the involvement of programmed cell death (PCD) in the process of inflated leaf petiole morphogenesis. In this paper, light and transmission electron microscopy (TEM) were used to investigate cytological events and the development of inflated leaf petiole. During this process, the inflated leaf petiole of Trapa pseudoincisa L. undergoes a developmental process, changing from solid to hollow phase. Debris from the degraded cells was seldom observed in the transverse sections of leaf petioles, but some degraded cells with an abnormal morphology were observed in longitudinal sections. Cytoplasmic changes, such as disrupted vacuoles, degraded plastids, and the emergence of secondary vacuoles were observed during leaf petiole morphogenesis. In addition, gel electrophoresis and TUNEL assays were used to evaluate DNA cleavage during petiole morphogenesis. DNA internucleosomal cleavage and TUNEL-positive nuclei indicate that the typical PCD features of DNA cleavage occurred early in the process. These results revealed that PCD plays a critical role in inflated leaf petiole morphogenesis. Additionally, a trans-disciplinary systems approach is required that recognises the necessity for integration of cytological and molecular characteristics for identification of aerenchyma type.

The complete chloroplast genome of Zelkova schneideriana (Rosales: Ulmaceae), an Endangered species endemic to China.

Zelkova schneideriana Hand.-Mazz. (Ulmaceae) is an endangered species endemic to China. In this study, we reported its complete chloroplast (cp) genome based on Illumina pair-end sequencing. The whole genome was 158,999 bp long, consisting of a pair of inverted repeat (IR) regions of 26,427 bp, a large single copy (LSC) region of 87,397 bp and a small single copy (SSC) region of 18,748 bp. The cp genome contained 133 genes, including 88 protein-coding genes (80 PCG species), 37 tRNA genes (30 tRNA species), and eight rRNA genes (4 rRNA species). The overall G+C content of the whole genome was 35.6%, and the corresponding values of the LSC, SSC, and IR regions were 33.0, 28.3, and 42.4%, respectively. The maximum likelihood phylogenetic analysis of 25 selected chloroplast genomes demonstrated that Z. schneideriana was closely related to Ulmus macrocarpa and Ulmus pumila.

Programmed Cell Death and Aerenchyma Formation in Water-Logged Sunflower Stems and Its Promotion by Ethylene and ROS.

Previous studies have shown that waterlogging/ hypoxic conditions induce aerenchyma formation to facilitate gas exchange. Ethylene (ET) and reactive oxygen species (ROS), as regulatory signals, might also be involved in these adaptive responses. However, the interrelationships between these signals have seldom been reported. Herein, we showed that programmed cell death (PCD) was involved in aerenchyma formation in the stem of Helianthus annuus. Lysigenous aerenchyma formation in the stem was induced through waterlogging (WA), ethylene and ROS. Pre-treatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) partially suppressed aerenchyma formation in the seedlings after treatment with WA, ET and 3-amino-1, 2, 4-triazole (AT, catalase inhibitor). In addition, pre-treatment with the ethylene perception inhibitor 1-methylcyclopropene (1-MCP) partially suppressed aerenchyma formation induced through WA and ET in the seedlings, but barely inhibited aerenchyma formation induced through ROS. These results revealed that ethylene-mediated ROS signaling plays a role in aerenchyma formation, and there is a causal and interdependent relationship during WA, ET and ROS in PCD, which regulates signal networks in the stem of H. annuus.

[An Extraction and Recognition Method of the Distributed Optical Fiber Vibration Signal Based on EMD-AWPP and HOSA-SVM Algorithm].

Given that the traditional signal processing methods can not effectively distinguish the different vibration intrusion signal, a feature extraction and recognition method of the vibration information is proposed based on EMD-AWPP and HOSA-SVM, using for high precision signal recognition of distributed fiber optic intrusion detection system. When dealing with different types of vibration, the method firstly utilizes the adaptive wavelet processing algorithm based on empirical mode decomposition effect to reduce the abnormal value influence of sensing signal and improve the accuracy of signal feature extraction. Not only the low frequency part of the signal is decomposed, but also the high frequency part the details of the signal disposed better by time-frequency localization process. Secondly, it uses the bispectrum and bicoherence spectrum to accurately extract the feature vector which contains different types of intrusion vibration. Finally, based on the BPNN reference model, the recognition parameters of SVM after the implementation of the particle swarm optimization can distinguish signals of different intrusion vibration, which endows the identification model stronger adaptive and self-learning ability. It overcomes the shortcomings, such as easy to fall into local optimum. The simulation experiment results showed that this new method can effectively extract the feature vector of sensing information, eliminate the influence of random noise and reduce the effects of outliers for different types of invasion source. The predicted category identifies with the output category and the accurate rate of vibration identification can reach above 95%. So it is better than BPNN recognition algorithm and improves the accuracy of the information analysis effectively.

De Novo Characterization of Flower Bud Transcriptomes and the Development of EST-SSR Markers for the Endangered Tree Tapiscia sinensis.

Tapiscia sinensis Oliv (Tapisciaceae) is an endangered species native to China famous for its androdioecious breeding system. However, there is a lack of genomic and transcriptome data on this species. In this study, the Tapiscia sinensis transcriptomes from two types of sex flower buds were sequenced. A total of 97,431,176 clean reads were assembled into 52,169 unigenes with an average length of 1116 bp. Through similarity comparison with known protein databases, 36,662 unigenes (70.27%) were annotated. A total of 10,002 (19.17%) unigenes were assigned to 124 pathways using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database. Additionally, 10,371 simple sequence repeats (SSRs) were identified in 8608 unigenes, with 16,317 pairs of primers designed for applications. 150 pairs of primers were chosen for further validation, and the 68 pairs (45.5%) were able to produce clear polymorphic bands. Six polymorphic SSR markers were used to Bayesian clustering analysis of 51 T. sinensis individuals. This is the first report to provide transcriptome information and to develop large-scale SSR molecular markers for T. sinensis. This study provides a valuable resource for conservation genetics and functional genomics research on T. sinensis for future work.

[The High Precision Analysis Research of Multichannel BOTDR Scattering Spectral Information Based on the TTDF and CNS Algorithm].

Traditional BOTDR optical fiber sensing system uses single channel sensing fiber to measure the information features. Uncontrolled factors such as cross-sensitivity can lead to a lower scattering spectrum fitting precision and make the information analysis deflection get worse. Therefore, a BOTDR system for detecting the multichannel sensor information at the same time is proposed. Also it provides a scattering spectrum analysis method for multichannel Brillouin optical time-domain reflection (BOT-DR) sensing system in order to extract high precision spectrum feature. This method combines the three times data fusion (TTDF) and the cuckoo Newton search (CNS) algorithm. First, according to the rule of Dixon and Grubbs criteria, the method uses the ability of TTDF algorithm in data fusion to eliminate the influence of abnormal value and reduce the error signal. Second, it uses the Cuckoo Newton search algorithm to improve the spectrum fitting and enhance the accuracy of Brillouin scattering spectrum information analysis. We can obtain the global optimal solution by smart cuckoo search. By using the optimal solution as the initial value of Newton algorithm for local optimization, it can ensure the spectrum fitting precision. The information extraction at different linewidths is analyzed in temperature information scattering spectrum under the condition of linear weight ratio of 1:9. The variances of the multichannel data fusion is about 0.0030, the center frequency of scattering spectrum is 11.213 GHz and the temperature error is less than 0.15 K. Theoretical analysis and simulation results show that the algorithm can be used in multichannel distributed optical fiber sensing system based on Brillouin optical time domain reflection. It can improve the accuracy of multichannel sensing signals and the precision of Brillouin scattering spectrum analysis effectively.

[A Brillouin Scattering Spectrum Feature Extraction Based on Flies Optimization Algorithm with Adaptive Mutation and Generalized Regression Neural Network].

According to the high precision extracting characteristics of scattering spectrum in Brillouin optical time domain reflection optical fiber sensing system, this paper proposes a new algorithm based on flies optimization algorithm with adaptive mutation and generalized regression neural network. The method takes advantages of the generalized regression neural network which has the ability of the approximation ability, learning speed and generalization of the model. Moreover, by using the strong search ability of flies optimization algorithm with adaptive mutation, it can enhance the learning ability of the neural network. Thus the fitting degree of Brillouin scattering spectrum and the extraction accuracy of frequency shift is improved. Model of actual Brillouin spectrum are constructed by Gaussian white noise on theoretical spectrum, whose center frequency is 11.213 GHz and the linewidths are 40-50, 30-60 and 20-70 MHz, respectively. Comparing the algorithm with the Levenberg-Marquardt fitting method based on finite element analysis, hybrid algorithm particle swarm optimization, Levenberg-Marquardt and the least square method, the maximum frequency shift error of the new algorithm is 0.4 MHz, the fitting degree is 0.991 2 and the root mean square error is 0.024 1. The simulation results show that the proposed algorithm has good fitting degree and minimum absolute error. Therefore, the algorithm can be used on distributed optical fiber sensing system based on Brillouin optical time domain reflection, which can improve the fitting of Brillouin scattering spectrum and the precision of frequency shift extraction effectively.

Leaf-shape remodeling: programmed cell death in fistular leaves of Allium fistulosum.

Some species of Allium in Liliaceae have fistular leaves. The fistular lamina of Allium fistulosum undergoes a process from solid to hollow during development. The aims were to reveal the process of fistular leaf formation involved in programmed cell death (PCD) and to compare the cytological events in the execution of cell death to those in the unusual leaf perforations or plant aerenchyma formation. In this study, light and transmission electron microscopy were used to characterize the development of fistular leaves and cytological events. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays and gel electrophoresis were used to determine nuclear DNA cleavage during the PCD. The cavity arises in the leaf blade by degradation of specialized cells, the designated pre-cavity cells, in the center of the leaves. Nuclei of cells within the pre-cavity site become TUNEL-positive, indicating that DNA cleavage is an early event. Gel electrophoresis revealed that DNA internucleosomal cleavage occurred resulting in a characteristic DNA ladder. Ultrastructural analysis of cells at the different stages showed disrupted vacuoles, misshapen nuclei with condensed chromatin, degraded cytoplasm and organelles and emergence of secondary vacuoles. The cell walls degraded last, and residue of degraded cell walls aggregated together. These results revealed that PCD plays a critical role in the development of A. fistulosum fistular leaves. The continuous cavity in A. fistulosum leaves resemble the aerenchyma in the pith of some gramineous plants to improve gas exchange.

Programmed cell death: a mechanism for the lysigenous formation of secretory cavities in leaves of Dictamnus dasycarpus.

The formation of secretory cavities in Rutaceae has been the subject of great interest. In this study, cytological events that are involved in the lysigenous formation of the secretory cavities in the leaves of Dictamnus dasycarpus are characterized by an interesting pattern of programmed cell death (PCD). During the developmental process, clusters of cells from a single protoepidermal cell embark on different trajectories and undergo different cell death fates: the cell walls of the secretory cells have characteristics of thinning or complete breakdown, while the sheath cells present a predominantly thick-walled feature. A DAPI assay shows deformed nuclei that are further confirmed to be TUNEL-positive. Gel electrophoresis indicates that DNA cleavage is random and does not result in ladder-like DNA fragmentation. Ultrastructurally, several remarkable features of PCD have been determined, such as misshapen nuclei with condensed chromatin and a significantly diffused membrane, degenerated mitochondria and plastids with disturbed membrane systems, multivesicular bodies, plastolysomes, vacuole disruption and lysis of the center secretory cell. Cytological evidence and Nile red stains exhibit abundant essential oils accumulated in degenerated outer secretory cells after the dissolution of the center secretory cell. In addition, explanations of taxonomic importance and the relationship between PCD and oil droplet accumulation in the secretory cavities are also discussed.

Programmed cell death during floral nectary senescence in Ipomoea purpurea.

The nectaries of Ipomoea purpurea wilt in the late flowering period. The senescence process of nectaries is frequently associated with cell lysis. In this paper, various techniques were used to investigate whether programmed cell death (PCD) was involved in the senescence process of nectaries in I. purpurea. Ultrastructural studies showed that nectary cells began to undergo structural distortion, chromatin condensation, mitochondrial membrane degradation, and vacuolar-membrane dissolution and rupture after bloom. 4',6-Diamidino-2-phenylindole (DAPI) and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine-5'-triphosphate (dUTP) nick end-labeling (TUNEL) assay showed that nectary cell nuclear DNA began to degrade during the budding stage, and disappeared in the fruiting stage. DNA gel electrophoresis showed that degradation of DNA was random. Together, these results suggest that PCD participate in the senescence of the nectary in I. purpurea. PCD began during the budding period, followed by significant changes in nectary morphology and structure during the flowering period. During the fruiting stage, the PCD process is complete and the nectary degrades.

From leaf and branch into a flower: Magnolia tells the story.

BACKGROUND: In the classical doctrines, Magnolia was frequently considered the archetype among flowering plants, and its conduplicate carpel with marginal placentation was assumed to be derived from a leaf-like organ bearing ovules along its margins. Although the robustness of this concept has been seriously questioned by advances in botanical research, especially the emergence of Magnolia deeper in the angiosperm tree of life in molecular systematics, it remains the most-taught interpretation for the origin of carpels. RESULTS: To test the validity of this classical doctrine, we performed comparative anatomical analyses of the vascular bundles in the flowers of Magnolia using fine (8-µm) paraffin -sections. We document the presence of two independent vascular systems in the carpels: the collateral bundles of the dorsal and ventral veins arising from the stelar bundle, and the amphicribral ovular bundles arising from the cortical bundles. This observation in conjunction with data from other fields concurrently suggests that the ovary wall is equivalent to a foliar organ whereas the placenta represents an ovule-bearing shoot. CONCLUSIONS: Our observation on the former model plant, Magnolia, nullifies the classical doctrine of carpel evolution and supports the Unifying Theory. This conclusion prompts a reconsideration of the concept of angiosperm flower evolution.

Laticiferous canal formation in fruits of Decaisnea fargesii: a programmed cell death process?

Programmed cell death (PCD), a topic of abiding interest, remodels plants at the cell, tissue, and organ levels involving various developmental processes of plants. The aim of this study is to provide a morphological characterization of evidence of PCD involvement in the laticiferous canal formation in fruit of Decaisnea fargesii. Several ultrastructural features of PCD have been observed including disintegration of vacuole and plasma membranes, cell wall degeneration, degenerated cytoplasm, abundant membrane structures and flocculent material, mitochondria and misshapen nuclei coupled with degraded plastids in vacuoles, and nuclei enveloped by rubber granule. In D. fargesii, the nuclei of the secretory epidermal cells become TUNEL-positive from the sunken stage to the late expanding stage, then DAPI-negative during the mature stage, indicating an early event of deoxyribonucleic acid (DNA) cleavage and a late event of complete DNA degeneration. Gel electrophoresis indicates that DNA cleavage is random and does not result in the laddering pattern indicating multiples of internucleosomal units. During the PCD of secretory epidermal cells, the rubber granules continue to be synthesized and accumulated in the secretory epidermal cells despite nuclear degradation. The PCD's role in laticiferous canal formation suggests that PCD may play important roles in gland development of plants.

[Dynamic changes of content of salvianolic acid in vegetative organs of Salvia miltiorrhiza].

OBJECTIVE: To determine the content of total salvianolic acid in different vegetative organs of Salvia miltiorrhiza and discover the dynamic change rules of tanshinol, protocatechuic aldehyde, caffeic acid and total salvianolic acid during the whole process of grwth. METHODS: HPLC-ECD was used. The separation was performed on Zorbax SB-C18 (150 mm x 4.6 mm, 5.0 microm) column by gradient elution. The mobile phase consisted of CH3OH-0.4% aqueous phosphoric acid. The flow rate was 1.0 mL/min. The detection was done at 0.7 V and the column temperature was 30 degrees C. RESULTS: The highest content of total salvianolic acid in leaf was in June and gradually dropped off till the lowest in December; The content of total salvianolic acid in leaf gradually decreased along with the growing of the leaf. The content of total salvianolic acid in root was high and consistent from July to September, but gradually dropped off till the lowest in November. CONCLUSION: The leaves of Salvia miltiorrhiza can be harvested in strong growth period to achieve the comprehensive use of the herb.

PDC1, a corn defensin peptide expressed in Escherichia coli and Pichia pastoris inhibits growth of Fusarium graminearum.

Plant defensin corn 1 (Pdc1) gene was amplified from corn genomic DNA with the primers designed from a corn EST sequence homologous to a barley defensin gene. The cloned gene contains two exons and an intron. The deduced 9KDa PDC1 peptide has a sequence that is identical to corn gamma2-zeathionin and has the typical features of a plant defensin, including a signal sequence of 35 amino acids, followed by a characteristic defensin domain of 47 amino acids containing 8 cysteines. The defensin protein was expressed from the cloned cDNA introduced into two different expression systems; prokaryotic, Escherichia coli and eukaryotic, yeast (Pichia pastoris). The PDC1 protein was purified with a nickel resin column and was tested for its antifungal activities using the pathogen Fusarium graminearum. The protein expressed in both E. coli and P. pastoris had antifungal activity, however the protein expressed in P. pastoris was more efficient in inhibiting growth of F. graminearum. FTIR analysis of PDC1 protein expressed in the two expression systems showed that expression in P. pastoris gave a product with more beta-sheets and less random unordered structure than when it was expressed in E. coli. In addition, removal of the His-tag used for purification increased the fungicidal activity of the PDC1 protein. The data presented here suggest that the defensin PDC1 peptide of corn could be effectively used to restrict the disease caused by F. graminearum.