Loss of function of pollen-expressed phospholipase OsMATL2 triggers haploid induction in japonica rice

CRISPR-Cas9-mediated editing of the pollen-expressed phospholipase A gene OsMATL2 triggers in planta haploid induction in japonica rice.

Genome-wide characterization of the soybean DOMAIN OF UNKNOWN FUNCTION 679 membrane protein gene family highlights their potential involvement in growth and stress response

The DMP (DUF679 membrane proteins) family is a plant-specific gene family that encodes membrane proteins. The DMP family genes are suggested to be involved in various programmed cell death processes and gamete fusion during double fertilization in Arabidopsis. However, their functional relevance in other crops remains unknown. This study identified 14 genes from the DMP family in soybean (Glycine max) and characterized their physiochemical properties, subcellular location, gene structure, and promoter regions using bioinformatics tools. Additionally, their tissue-specific and stress-responsive expressions were analyzed using publicly available transcriptome data. Phylogenetic analysis of 198 DMPs from monocots and dicots revealed six clades, with clade-I encoding senescence-related AtDMP1/2 orthologues and clade-II including pollen-specific AtDMP8/9 orthologues. The largest clade, clade-III, predominantly included monocot DMPs, while monocot- and dicot-specific DMPs were assembled in clade-IV and clade-VI, respectively. Evolutionary analysis suggests that soybean GmDMPs underwent purifying selection during evolution. Using 68 transcriptome datasets, expression profiling revealed expression in diverse tissues and distinct responses to abiotic and biotic stresses. The genes Glyma.09G237500 and Glyma.18G098300 showed pistil-abundant expression by qPCR, suggesting they could be potential targets for female organ-mediated haploid induction. Furthermore, cis-acting regulatory elements primarily related to stress-, hormone-, and light-induced pathways regulate GmDMPs, which is consistent with their divergent expression and suggests involvement in growth and stress responses. Overall, our study provides a comprehensive report on the soybean GmDMP family and a framework for further biological functional analysis of DMP genes in soybean or other crops.

A group III patatin-like phospholipase gene pPLAIIIδ regulates lignin biosynthesis and influences the rate of seed germination in Arabidopsis thaliana

The lignification of plant secondary walls is an important process that provides plants with mechanical support. However, the presence of lignin in the secondary walls affects the readily availability of cellulose required in various industries, including the biofuel, paper, and textile industries. Thus, plants with less lignin are ideal for usage in such industries. Molecular studies have identified genes that regulate plant lignification, including group III plant-specific patatin-related phospholipase genes. Recent studies have reported decreased lignin content when pPLAIIIα, pPLAIIIγ (from Arabidopsis thaliana), and pPLAIIIβ (from Panax ginseng) were overexpressed in Arabidopsis. However, the role played by a closely related gene pPLAIIIδ in lignin biosynthesis has not yet been reported. In this study, we found that overexpression of the pPLAIIIδ significantly reduced the lignin content in secondary cell walls, whereas the silencing of the gene increased secondary walls lignification. Transcript level analysis showed that the key structural and regulatory genes involved in the lignin biosynthesis pathway decreased in overexpression, and increased in plants with silenced pPLAIIIδ. Further analysis revealed that pPLAIIIδ played an influential role in several physiological processes including seed germination, and chlorophyll accumulation. Moreover, the gene also influenced the size of plants and plant organs, including leaves, seeds, and root hairs. Generally, our study provides important insights toward the use of genetic engineering for lignin reduction in plants and provides information about the agronomical and physiological suitability of pPLAIIIδ transgenic plants for utilization in biomass processing industries.

Loss-of-function of gynoecium-expressed phospholipase pPLAIIγ triggers maternal haploid induction in Arabidopsis

Production of in planta haploid embryos that inherit chromosomes from only one parent can greatly increase breeding efficiency via quickly generating homozygous plants, called doubled haploid. One of the main players of in planta haploid induction is a pollen-specific phospholipase A, which is able, when mutated, to induce in vivo haploid induction in numerous monocots. However, no functional orthologous gene has been identified in dicots plants. Here, we show that loss-of-function of gynoecium-expressed phospholipase AII (pPLAIIγ) triggers maternal haploid plants in Arabidopsis, at an average rate of 1.07%. Reciprocal crosses demonstrate that haploid plants are triggered from the female side and not from the pollen, and the haploid plants carry the maternal genome. Promoter activity of pPLAIIγ shows enriched expression in the funiculus of flower development stages 13 and 18, and pPLAIIγ fused to yellow fluorescent protein reveals a plasma-membrane localization Interestingly, the polar localized PIN1 at the basal plasma membrane of the funiculus was all internalized in pplaIIγ mutants, suggesting that altered PIN1 localization in female organ could play a role in maternal haploid induction.

Overexpression of pPLAIIIγ in Arabidopsis Reduced Xylem Lignification of Stem by Regulating Peroxidases

Patatin-related phospholipases A (pPLAs) are a group of plant-specific acyl lipid hydrolases that share less homology with phospholipases than that observed in other organisms. Out of the three known subfamilies (pPLAI, pPLAII, and pPLAIII), the pPLAIII member of genes is particularly known for modifying the cell wall structure, resulting in less lignin content. Overexpression of pPLAIIIα and ginseng-derived PgpPLAIIIβ in Arabidopsis and hybrid poplar was reported to reduce the lignin content. Lignin is a complex racemic phenolic heteropolymer that forms the key structural material supporting most of the tissues in plants and plays an important role in the adaptive strategies of vascular plants. However, lignin exerts a negative impact on the utilization of plant biomass in the paper and pulp industry, forage digestibility, textile industry, and production of biofuel. Therefore, the overexpression of pPLAIIIγ in Arabidopsis was analyzed in this study. This overexpression led to the formation of dwarf plants with altered anisotropic growth and reduced lignification of the stem. Transcript levels of lignin biosynthesis-related genes, as well as lignin-specific transcription factors, decreased. Peroxidase-mediated oxidation of monolignols occurs in the final stage of lignin polymerization. Two secondary cell wall-specific peroxidases were downregulated following lowered H₂O₂ levels, which suggests a functional role of peroxidase in the reduction of lignification by pPLAIIIγ when overexpressed in Arabidopsis.

The Reduced Longitudinal Growth Induced by Overexpression of pPLAIIIγ Is Regulated by Genes Encoding Microtubule-Associated Proteins

There are three subfamilies of patatin-related phospholipase A (pPLA) group of genes: pPLAI, pPLAII, and pPLAIII. Among the four members of pPLAIIIs (α, β, γ, δ), the overexpression of three isoforms (α, β, and δ) displayed distinct morphological growth patterns, in which the anisotropic cell expansion was disrupted. Here, the least studied pPLAIIIγ was characterized, and it was found that the overexpression of pPLAIIIγ in Arabidopsis resulted in longitudinally reduced cell expansion patterns, which are consistent with the general phenotype induced by pPLAIIIs overexpression. The microtubule-associated protein MAP18 was found to be enriched in a pPLAIIIδ overexpressing line in a previous study. This indicates that factors, such as microtubules and ethylene biosynthesis, are involved in determining the radial cell expansion patterns. Microtubules have long been recognized to possess functional key roles in the processes of plant cells, including cell division, growth, and development, whereas ethylene treatment was reported to induce the reorientation of microtubules. Thus, the possible links between the altered anisotropic cell expansion and microtubules were studied. Our analysis revealed changes in the transcriptional levels of microtubule-associated genes, as well as phospholipase D (PLD) genes, upon the overexpression of pPLAIIIγ. Overall, our results suggest that the longitudinally reduced cell expansion observed in pPLAIIIγ overexpression is driven by microtubules via transcriptional modulation of the PLD and MAP genes. The altered transcripts of the genes involved in ethylene-biosynthesis in pPLAIIIγOE further support the conclusion that the typical phenotype is derived from the link with microtubules.

Genome-enabled discovery of anthraquinone biosynthesis in Senna tora

Senna tora is a widely used medicinal plant. Its health benefits have been attributed to the large quantity of anthraquinones, but how they are made in plants remains a mystery. To identify the genes responsible for plant anthraquinone biosynthesis, we reveal the genome sequence of S. tora at the chromosome level with 526 Mb (96%) assembled into 13 chromosomes. Comparison among related plant species shows that a chalcone synthase-like (CHS-L) gene family has lineage-specifically and rapidly expanded in S. tora. Combining genomics, transcriptomics, metabolomics, and biochemistry, we identify a CHS-L gene contributing to the biosynthesis of anthraquinones. The S. tora reference genome will accelerate the discovery of biologically active anthraquinone biosynthesis pathways in medicinal plants.

Genome-enabled discovery of anthraquinone biosynthesis in Senna tora

Senna tora is a widely used medicinal plant. Its health benefits have been attributed to the large quantity of anthraquinones, but how they are made in plants remains a mystery. To identify the genes responsible for plant anthraquinone biosynthesis, we reveal the genome sequence of S. tora at the chromosome level with 526 Mb (96%) assembled into 13 chromosomes. Comparison among related plant species shows that a chalcone synthase-like (CHS-L) gene family has lineage-specifically and rapidly expanded in S. tora. Combining genomics, transcriptomics, metabolomics, and biochemistry, we identify a CHS-L gene contributing to the biosynthesis of anthraquinones. The S. tora reference genome will accelerate the discovery of biologically active anthraquinone biosynthesis pathways in medicinal plants.

Phospholipase pPLAIIIα Increases Germination Rate and Resistance to Turnip Crinkle Virus when Overexpressed

Patatin-related phospholipase As (pPLAs) are major hydrolases acting on acyl-lipids and play important roles in various plant developmental processes. pPLAIII group members, which lack a canonical catalytic Ser motif, have been less studied than other pPLAs. We report here the characterization of pPLAIIIα in Arabidopsis (Arabidopsis thaliana) based on the biochemical and physiological characterization of pPLAIIIα knockouts, complementants, and overexpressors, as well as heterologous expression of the protein. In vitro activity assays on the purified recombinant protein showed that despite lack of canonical phospholipase motifs, pPLAIIIα had a phospholipase A activity on a wide variety of phospholipids. Overexpression of pPLAIIIα in Arabidopsis resulted in a decrease in many lipid molecular species, but the composition in major lipid classes was not affected. Fluorescence tagging indicated that pPLAIIIα localizes to the plasma membrane. Although Arabidopsis pplaIIIα knockout mutants showed some phenotypes comparable to other pPLAIIIs, such as reduced trichome length and increased hypocotyl length, control of seed size and germination were identified as distinctive pPLAIIIα-mediated functions. Expression of some PLD genes was strongly reduced in the pplaIIIα mutants. Overexpression of pPLAIIIα caused increased resistance to turnip crinkle virus, which associated with a 2-fold higher salicylic acid/jasmonic acid ratio and an increased expression of the defense gene pathogenesis-related protein1. These results therefore show that pPLAIIIα has functions that overlap with those of other pPLAIIIs but also distinctive functions, such as the control of seed germination. This study also provides new insights into the pathways downstream of pPLAIIIα.

Ginseng-derived patatin-related phospholipase PgpPLAIIIβ alters plant growth and lignification of xylem in hybrid poplars

Patatin-liked phospholipase A (pPLAs) are major lipid acyl hydrolases that participate in various biological functions in plant growth and development. Previously, a ginseng-derived pPLAIII homolog was reported to reduce lignin content in Arabidopsis. This led us to evaluate its possible usefulness as a biomass source in wood plant. Herein, we report that there are six members in the pPLAIII gene family in poplar. Overexpression of pPLAIIIβ derived from ginseng resulted in a reduced plant height with radially expanded stem growth in hybrid poplars. Compared with the wild type (WT), the chlorophyll content was increased in the overexpression poplar lines, whereas the leaf size was smaller. The secondary cell wall structure in overexpression lines was also altered, exhibiting reduced lignification in the xylem. Two transcription factors, MYB92 and MYB152, which control lignin biosynthesis, were downregulated in the overexpression lines. The middle xylem of the overexpression line showed heavy thickening, making it thicker than the other xylem parts and the WT xylem, which rather could have been contributed by the presence of more cellulose in the selected surface area. Taken together, the results suggest that PgpPLAIIIβ plays a role not only in cell elongation patterns, but also in determining the secondary cell wall composition.

Overexpression of ginseng cytochrome P450 CYP736A12 alters plant growth and confers phenylurea herbicide tolerance in Arabidopsis

Background

Cytochrome P450 enzymes catalyze a wide range of reactions in plant metabolism. Besides their physiological functions on primary and secondary metabolites, P450s are also involved in herbicide detoxification via hydroxylation or dealkylation. Ginseng as a perennial plant offers more sustainable solutions to herbicide resistance.

Methods

Tissue-specific gene expression and differentially modulated transcripts were monitored by quantitative real-time polymerase chain reaction. As a tool to evaluate the function of PgCYP736A12, the 35S promoter was used to overexpress the gene in Arabidopsis. Protein localization was visualized using confocal microscopy by tagging the fluorescent protein. Tolerance to herbicides was analyzed by growing seeds and seedlings on Murashige and Skoog medium containing chlorotoluron.

Results

The expression of PgCYP736A12 was three-fold more in leaves compared with other tissues from two-year-old ginseng plants. Transcript levels were similarly upregulated by treatment with abscisic acid, hydrogen peroxide, and NaCl, the highest being with salicylic acid. Jasmonic acid treatment did not alter the mRNA levels of PgCYP736A12. Transgenic lines displayed slightly reduced plant height and were able to tolerate the herbicide chlorotoluron. Reduced stem elongation might be correlated with increased expression of genes involved in bioconversion of gibberellin to inactive forms. PgCYP736A12 protein localized to the cytoplasm and nucleus.

Conclusion

PgCYP736A12 does not respond to the well-known secondary metabolite elicitor jasmonic acid, which suggests that it may not function in ginsenoside biosynthesis. Heterologous overexpression of PgCYP736A12 reveals that this gene is actually involved in herbicide metabolism.

Overexpression of ginseng patatin-related phospholipase pPLAIIIβ alters the polarity of cell growth and decreases lignin content in Arabidopsis

Background

The patatin-related phospholipase AIII family (pPLAIIIs) genes alter cell elongation and cell wall composition in Arabidopsis and rice plant, suggesting diverse commercial purposes of the economically important medicinal ginseng plant. Herein, we show the functional characterization of a ginseng pPLAIII gene for the first time and discuss its potential applications.

Methods

pPLAIIIs were identified from ginseng expressed sequence tag clones and further confirmed by search against ginseng database and polymerase chain reaction. A clone showing the highest homology with pPLAIIIβ was shown to be overexpressed in Arabidopsis using Agrobacterium. Quantitative polymerase chain reaction was performed to analyze ginseng pPLAIIIβ expression. Phenotypes were observed using a low-vacuum scanning electron microscope. Lignin was stained using phloroglucinol and quantified using acetyl bromide.

Results

The PgpPLAIIIβ transcripts were observed in all organs of 2-year-old ginseng. Overexpression of ginseng pPLAIIIβ (PgpPLAIIIβ-OE) in Arabidopsis resulted in small and stunted plants. It shortened the trichomes and decreased trichome number, indicating defects in cell polarity. Furthermore, OE lines exhibited enlarged seeds with less number per silique. The YUCCA9 gene was downregulated in the OE lines, which is reported to be associated with lignification. Accordingly, lignin was stained less in the OE lines, and the expression of two transcription factors related to lignin biosynthesis was also decreased significantly.

Conclusion

Overexpression of pPLAIIIβ retarded cell elongation in all the tested organs except seeds, which were longer and thicker than those of the controls. Shorter root length is related to auxin-responsive genes, and its stunted phenotype showed decreased lignin content.

cis-Prenyltransferase interacts with a Nogo-B receptor homolog for dolichol biosynthesis in Panax ginseng Meyer

Background

Prenyltransferases catalyze the sequential addition of isopentenyl diphosphate units to allylic prenyl diphosphate acceptors and are classified as either trans-prenyltransferases (TPTs) or cis-prenyltransferases (CPTs). The functions of CPTs have been well characterized in bacteria, yeast, and mammals compared to plants. The characterization of CPTs also has been less studied than TPTs. In the present study, molecular cloning and functional characterization of a CPT from a medicinal plant, Panax ginseng Mayer were addressed.

Methods

Gene expression patterns of PgCPT1 were analyzed by quantitative reverse transcription polymerase chain reaction. In planta transformation was generated by floral dipping using Agrobacterium tumefaciens. Yeast transformation was performed by lithium acetate and heat-shock for rer2Δ complementation and yeast-two-hybrid assay.

Results

The ginseng genome contains at least one family of three putative CPT genes. PgCPT1 is expressed in all organs, but more predominantly in the leaves. Overexpression of PgCPT1 did not show any plant growth defect, and its protein can complement yeast mutant rer2Δ via possible protein–protein interaction with PgCPTL2.

Conclusion

Partial complementation of the yeast dolichol biosynthesis mutant rer2Δ suggested that PgCPT1 is involved in dolichol biosynthesis. Direct protein interaction between PgCPT1 and a human Nogo-B receptor homolog suggests that PgCPT1 requires an accessory component for proper function.

Overexpression of ginseng UGT72AL1 causes organ fusion in the axillary leaf branch of Arabidopsis

Background

Glycosylation of natural compounds increases the diversity of secondary metabolites. Glycosylation steps are implicated not only in plant growth and development, but also in plant defense responses. Although the activities of uridine-dependent glycosyltransferases (UGTs) have long been recognized, and genes encoding them in several higher plants have been identified, the specific functions of UGTs in planta remain largely unknown.

Methods

Spatial and temporal patterns of gene expression were analyzed by quantitative reverse transcription (qRT)-polymerase chain reaction (PCR) and GUS histochemical assay. In planta transformation in heterologous Arabidopsis was generated by floral dipping using Agrobacterium tumefaciens (C58C1). Protein localization was analyzed by confocal microscopy via fluorescent protein tagging.

Results

PgUGT72AL1 was highly expressed in the rhizome, upper root, and youngest leaf compared with the other organs. GUS staining of the promoter: GUS fusion revealed high expression in different organs, including axillary leaf branch. Overexpression of PgUGT72AL1 resulted in a fused organ in the axillary leaf branch.

Conclusion

PgUGT72AL1, which is phylogenetically close to PgUGT71A27, is involved in the production of ginsenoside compound K. Considering that compound K is not reported in raw ginseng material, further characterization of this gene may shed light on the biological function of ginsenosides in ginseng plant growth and development. The organ fusion phenotype could be caused by the defective growth of cells in the boundary region, commonly regulated by phytohormones such as auxins or brassinosteroids, and requires further analysis.

Leaf-specific pathogenesis-related 10 homolog, PgPR-10.3, shows in silico binding affinity with several biologically important molecules

BACKGROUND

Pathogenesis-related 10 (PR-10) proteins are small, cytosolic proteins with a similar three-dimensional structure. Crystal structures for several PR-10 homologs have similar overall folding patterns, with an unusually large internal cavity that is a binding site for biologically important molecules. Although structural information on PR-10 proteins is substantial, understanding of their biological function remains limited. Here, we showed that one of the PgPR-10 homologs, PgPR-10.3, shares binding properties with flavonoids, kinetin, emodin, deoxycholic acid, and ginsenoside Re (1 of the steroid glycosides).

METHODS

Gene expression patterns of PgPR-10.3 were analyzed by quantitative real-time PCR. The three-dimensional structure of PgPR-10 proteins was visualized by homology modeling, and docking to retrieve biologically active molecules was performed using AutoDock4 program.

RESULTS

Transcript levels of PgPR-10.3 expressed in leaves, stems, and roots of 3-wk-old ginseng plantlets were on average 86-fold lower than those of PgPR-10.2. In mature 2-yr-old ginseng plants, the mRNA of PgPR-10.3 is restricted to leaves. Ginsenoside Re production is especially prominent in leaves of Panax ginseng Meyer, and the binding property of PgPR-10.3 with ginsenoside Re suggests that this protein has an important role in the control of secondary metabolism.

CONCLUSION

Although ginseng PR-10.3 gene is expressed in all organs of 3-wk-old plantlets, its expression is restricted to leaves in mature 2-yr-old ginseng plants. The putative binding property of PgPR-10.3 with Re is intriguing. Further verification of binding affinity with other biologically important molecules in the large hydrophobic cavity of PgPR-10.3 may provide an insight into the biological features of PR-10 proteins.

Functional analysis of 3-hydroxy-3-methylglutaryl coenzyme a reductase encoding genes in triterpene saponin-producing ginseng

Ginsenosides are glycosylated triterpenes that are considered to be important pharmaceutically active components of the ginseng (Panax ginseng 'Meyer') plant, which is known as an adaptogenic herb. However, the regulatory mechanism underlying the biosynthesis of triterpene saponin through the mevalonate pathway in ginseng remains unclear. In this study, we characterized the role of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) concerning ginsenoside biosynthesis. Through analysis of full-length complementary DNA, two forms of ginseng HMGR (PgHMGR1 and PgHMGR2) were identified as showing high sequence identity. The steady-state mRNA expression patterns of PgHMGR1 and PgHMGR2 are relatively low in seed, leaf, stem, and flower, but stronger in the petiole of seedling and root. The transcripts of PgHMGR1 were relatively constant in 3- and 6-year-old ginseng roots. However, PgHMGR2 was increased five times in the 6-year-old ginseng roots compared with the 3-year-old ginseng roots, which indicates that HMGRs have constant and specific roles in the accumulation of ginsenosides in roots. Competitive inhibition of HMGR by mevinolin caused a significant reduction of total ginsenoside in ginseng adventitious roots. Moreover, continuous dark exposure for 2 to 3 d increased the total ginsenosides content in 3-year-old ginseng after the dark-induced activity of PgHMGR1. These results suggest that PgHMGR1 is associated with the dark-dependent promotion of ginsenoside biosynthesis. We also observed that the PgHMGR1 can complement Arabidopsis (Arabidopsis thaliana) hmgr1-1 and that the overexpression of PgHMGR1 enhanced the production of sterols and triterpenes in Arabidopsis and ginseng. Overall, this finding suggests that ginseng HMGRs play a regulatory role in triterpene ginsenoside biosynthesis.

Functional analysis of 3-hydroxy-3-methylglutaryl coenzyme a reductase encoding genes in triterpene saponin-producing ginseng

Ginsenosides are glycosylated triterpenes that are considered to be important pharmaceutically active components of the ginseng (Panax ginseng 'Meyer') plant, which is known as an adaptogenic herb. However, the regulatory mechanism underlying the biosynthesis of triterpene saponin through the mevalonate pathway in ginseng remains unclear. In this study, we characterized the role of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) concerning ginsenoside biosynthesis. Through analysis of full-length complementary DNA, two forms of ginseng HMGR (PgHMGR1 and PgHMGR2) were identified as showing high sequence identity. The steady-state mRNA expression patterns of PgHMGR1 and PgHMGR2 are relatively low in seed, leaf, stem, and flower, but stronger in the petiole of seedling and root. The transcripts of PgHMGR1 were relatively constant in 3- and 6-year-old ginseng roots. However, PgHMGR2 was increased five times in the 6-year-old ginseng roots compared with the 3-year-old ginseng roots, which indicates that HMGRs have constant and specific roles in the accumulation of ginsenosides in roots. Competitive inhibition of HMGR by mevinolin caused a significant reduction of total ginsenoside in ginseng adventitious roots. Moreover, continuous dark exposure for 2 to 3 d increased the total ginsenosides content in 3-year-old ginseng after the dark-induced activity of PgHMGR1. These results suggest that PgHMGR1 is associated with the dark-dependent promotion of ginsenoside biosynthesis. We also observed that the PgHMGR1 can complement Arabidopsis (Arabidopsis thaliana) hmgr1-1 and that the overexpression of PgHMGR1 enhanced the production of sterols and triterpenes in Arabidopsis and ginseng. Overall, this finding suggests that ginseng HMGRs play a regulatory role in triterpene ginsenoside biosynthesis.

Spermidine alleviates the growth of saline-stressed ginseng seedlings through antioxidative defense system

Protective effects of exogenous spermidine (Spd), activity of antioxygenic enzymes, and levels of free radicals in a well-known medicinal plant, Panax ginseng was examined. Seedlings grown in salinized nutrient solution (150 mM NaCl) for 7d exhibited reduced relative water content, plant growth, increased free radicals, and showing elevated lipid peroxidation. Application of Spd (0.01, 0.1, and 1mM) to the salinized nutrient solution showed increased plant growth by preventing chlorophyll degradation and increasing PA levels, as well as antioxidant enzymes such as CAT, APX, and GPX activity in the seedlings of ginseng. During salinity stress, Spd was effective for lowering the accumulation of putrescine (Put), with a significant increase in the spermidine (Spd) and spermine (Spm) levels in the ginseng seedlings. A decline in the Put level ran parallel to the higher accumulation of proline (Pro), and exogenous Spd also resulted in the alleviation of Pro content under salinity. Hydrogen peroxide (H2O2) and superoxide (O2(-)) production rates were also reduced in stressed plants after Spd treatment. Furthermore, the combined effect of Spd and salt led to a significant increase in diamine oxidase (DAO), and subsequent decline in polyamine oxidase (PAO). These positive effects were observed in 0.1 and 1mM Spd concentrations, but a lower concentration (0.01 mM) had a very limited effect. In summary, application of exogenous Spd could enhance salt tolerance of P. ginseng by enhancing the activities of enzyme scavenging system, which influence the intensity of oxidative stress.

Acclimation of hydrogen peroxide enhances salt tolerance by activating defense-related proteins in Panax ginseng C.A. Meyer

The effect of exogenously applied hydrogen peroxide on salt stress tolerance was investigated in Panax ginseng. Pretreatment of ginseng seedlings with 100 μM H2O2 increased the physiological salt tolerance of the ginseng plant and was used as the optimum concentration to induce salt tolerance capacity. Treatment with exogenous H2O2 for 2 days significantly enhanced salt stress tolerance in ginseng seedlings by increasing the activities of ascorbate peroxidase, catalase and guaiacol peroxidase and by decreasing the concentrations of malondialdehyde (MDA) and endogenous H2O2 as well as the production rate of superoxide radical (O2(-)). There was a positive physiological effect on the growth and development of salt-stressed seedlings by exogenous H2O2 as measured by ginseng dry weight and both chlorophyll and carotenoid contents. Exogenous H2O2 induced changes in MDA, O2(-), antioxidant enzymes and antioxidant compounds, which are responsible for increases in salt stress tolerance. Salt treatment caused drastic declines in ginseng growth and antioxidants levels; whereas, acclimation treatment with H2O2 allowed the ginseng seedlings to recover from salt stress by up-regulation of defense-related proteins such as antioxidant enzymes and antioxidant compounds.

Isolation and Characterization of a Theta Glutathione S-transferase Gene from Panax ginseng Meyer

Plants have versatile detoxification systems to encounter the phytotoxicity of the wide range of natural and synthetic compounds present in the environment. Glutathione S-transferase (GST) is an enzyme that detoxifies natural and exogenous toxic compounds by conjugation with glutathione (GSH). Recently, several roles of GST giving stress tolerance in plants have demonstrated, but little is known about the role of ginseng GSTs. Therefore, this work aimed to provide further information on the GST gene present in Panax ginseng genome as well as its expression and function. A GST cDNA (PgGST) was isolated from P. ginseng cDNA library, and it showed the amino acid sequence similarity with theta type of GSTs. PgGST in ginseng plant was induced by exposure to metals, plant hormone, heavy metals, and high light irradiance. To improve the resistance against environmental stresses, full-length cDNA of PgGST was introduced into Nicotiana tabacum. Overexpression of PgGST led to twofold increase in GST-specific activity compared to the non-transgenic plants, and the GST overexpressed plant showed resistance against herbicide phosphinothricin. The results suggested that the PgGST isolated from ginseng might have a role in the protection mechanism against toxic materials such as heavy metals and herbicides.

Transcript pattern of cytochrome P450, antioxidant and ginsenoside biosynthetic pathway genes under heavy metal stress in Panax ginseng Meyer

The differential transcript patterns of five antioxidant genes, four genes related to the ginsenoside pathway and five P450 genes related to defense mechanism were investigated in in vitro adventitious roots of Panax ginseng after exposure to two different concentrations of heavy metals for 7 days. PgSOD-1 and PgCAT transcription increased in a dose-dependent manner during the exposure to CuCl(2), NiCl(2), and CdCl(2), while all other tested scavenging enzymes didn't show significant increase during heavy metal exposure. Conversely, the mRNA transcripts of PgSQE, PgDDS were highly responsive to CuCl(2) compared to NiCl(2) exposure. However, the transcript profile of Pgβ-AS was highly induced upon NiCl(2) treatment compared to CuCl(2) and CdCl(2) exposure. The expressions of PgCYP716A42, PgCYP71A50U, and PgCYP82C22 were regulated in similar manners, and all showed the highest transcript profile at 100 μM of CuCl(2), CdCl(2), and NiCl(2) except PgCYP71D184, which showed the highest transcript level when subjected to 10 μM CuCl(2) and NiCl(2). Thus it may suggest that in P. ginseng heavy metal interaction on cell membrane induced expression of various defense related genes via jasmonic acid pathway and also possesses cross talk networks with other defense related pathways.

Cytoplasm localization of aminopeptidase M1 and its functional activity in root hair cells and BY-2 cells

Aminopeptidase M1 (APM1) was the first M1 metallopeptidase family member identified in Arabidopsis, isolated by its affinity for the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). A loss-of-function mutation showed various developmental defects in cell division and auxin transport. APM1 was shown to be localized in endomembrane structures, the cytoplasm, and the plasma membrane. These previous results suggested that APM1 has diverse functional roles in different cell and tissue types. Here we report that APM1 localized to the cytoplasm, and its over-expression in the root hair cell caused longer root hair phenotypes. Treatment of aminopeptidase inhibitors caused internalization of auxin efflux PIN-FORMED proteins in root hair cells and suppressed short root hair phenotype of PIN3 overexpression line (PIN3ox). APM1 also localized to the cytoplasm in tobacco BY-2 cells, its over-expression had little effect on auxin transport in these cells.

High Frequency of Plant Regeneration through Cyclic Secondary Somatic Embryogenesis in Panax ginseng

Somatic embryogenesis is one of good examples of the basic research for plant embryo development as well as an important technique for plant biotechnology such as medicinally important plants. Single embryos develop into normal plantlets with shoots and roots. Therefore, direct single embryogenesis derived from single cells is highly important for normal plant regeneration. Here we demonstrate that the cyclic secondary somatic embryogenesis in Panax ginseng Meyer is a permanent source of embryogenic material that can be used for genetic manipulations. Secondary somatic embryos were originated directly from the primary somatic embryos on hormone-free Murashige and Skoog medium, and proliferated further in a cyclic manner. EM medium (one third of modified MS medium [MS medium containing half amount of NH4NO3 and KNO3] with 2% to 3% sucrose) favored further development of proliferated secondary somatic embryos into plantlets with root system. The plantlets developed into plants with well-developed taproots in half-strength Schenk and Hildebrandt basal medium supplemented with 0.5% activated charcoal.

Classification and characterization of putative cytochrome P450 genes from Panax ginseng C. A. Meyer

In plants heme containing cytochrome P450 (P450) is a superfamily of monooxygenases that catalyze the addition of one oxygen atom from O2 into a substrate, with a substantial reduction of the other atom to water. The function of P450 families is attributed to chemical defense mechanism under terrestrial environmental conditions; several are involved in secondary and hormone metabolism. However, the evolutionary relationships of P450 genes in Panax ginseng remain largely unknown. In the present study, data mining methods were implemented and 116 novel putative P450 genes were identified from Expressed Sequence Tags (ESTs) of a ginseng database. These genes were classified into four clans and 22 families by sequence similarity conducted at amino acid level. The representative putative P450 sequences of P. ginseng and known P450 family from other plants were used to construct a phylogenetic tree. By comparing with other genomes, we found that most of the P450 genes from P. ginseng can be found in other dicot species. Depending on P450 family functions, seven P450 genes were selected, and for that organ specific expression, abiotic, and biotic studies were performed by quantitative reverse transcriptase-polymerase chain reaction. Different genes were found to be expressed differently in different organs. Biotic stress and abiotic stress transcript level was regulated diversely, and upregulation of P450 genes indicated the involvement of certain genes under stress conditions. The upregulation of the P450 genes under methyl jasmonate and fungal stress justifies the involvement of specific genes in secondary metabolite biosynthesis. Our results provide a foundation for further elucidating the actual function and role of P450 involved in various biochemical pathways in P. ginseng.

Authentication of medicinal plants by SNP-based multiplex PCR

Highly variable intergenic spacer and intron regions from nuclear and cytoplasmic DNA have been used for species identification. Noncoding internal transcribed spacers (ITSs) located in 18S-5.8S-26S, and 5S ribosomal RNA genes (rDNAs) represent suitable region for medicinal plant authentication. Noncoding regions from two cytoplasmic DNA, chloroplast DNA (trnT-F intergenic spacer region), and mitochondrial DNA (fourth intron region of nad7 gene) are also successfully applied for the proper identification of medicinal plants. Single-nucleotide polymorphism (SNP) sites obtained from the amplification of intergenic spacer and intron regions are properly utilized for the verification of medicinal plants in species level using multiplex PCR. Multiplex PCR as a variant of PCR technique used to amplify more than two loci simultaneously.

Expression and stress tolerance of PR10 genes from Panax ginseng C. A. Meyer

Pathogenesis-related 10 protein families (PgPR10 proteins) from ginseng are reported to have ribonuclease activity, conferring defense-related resistance against various stresses. Homology-based PCR using PgPR10-2 specific primers allowed for the isolation of two additional PgPR10 genes. PgPR10-1 is identical to the previously reported ribonuclease 1, while PgPR10-3 is a newly-discovered protein, suggesting that the PgPR10s are a multi-gene family. Differential organ-specific transcripts of PgPR10-1 and PgPR10-2 in the flower bud and root, respectively, indicate that there are tissue-specific functional roles for this gene family. Overexpression of PgPR10-2 in Arabidopsis conferred longer root length and a tolerant growth phenotype on NaCl-supplemented media. Further changes in transcriptional levels against sets of abiotic stressors suggest similar functional roles of PgPR10-1 in the root and predominantly in the flower organ based on its higher expression levels. Overall, this suggests that the manipulation of PgPR10 genes in plants can be used as valuable tool to enhance its physiological status.

phot1 inhibition of ABCB19 primes lateral auxin fluxes in the shoot apex required for phototropism

It is well accepted that lateral redistribution of the phytohormone auxin underlies the bending of plant organs towards light. In monocots, photoreception occurs at the shoot tip above the region of differential growth. Despite more than a century of research, it is still unresolved how light regulates auxin distribution and where this occurs in dicots. Here, we establish a system in Arabidopsis thaliana to study hypocotyl phototropism in the absence of developmental events associated with seedling photomorphogenesis. We show that auxin redistribution to the epidermal sites of action occurs at and above the hypocotyl apex, not at the elongation zone. Within this region, we identify the auxin efflux transporter ATP-BINDING CASSETTE B19 (ABCB19) as a substrate target for the photoreceptor kinase PHOTOTROPIN 1 (phot1). Heterologous expression and physiological analyses indicate that phosphorylation of ABCB19 by phot1 inhibits its efflux activity, thereby increasing auxin levels in and above the hypocotyl apex to halt vertical growth and prime lateral fluxes that are subsequently channeled to the elongation zone by PIN-FORMED 3 (PIN3). Together, these results provide new insights into the roles of ABCB19 and PIN3 in establishing phototropic curvatures and demonstrate that the proximity of light perception and differential phototropic growth is conserved in angiosperms.

Plants depend on sunlight for photosynthesis and adapt their growth to optimize light capture. Phototropism, the reorientation of growth towards light, is one important adaptive response. Modern studies of phototropism began with experiments in monocotyledonous grasses by Charles Darwin and led ultimately to the discovery of the plant growth hormone auxin, establishing the concept that light perception at the shoot apex triggers differential bending in the tissues below. In the past two decades, molecular-genetic analysis in the model flowering plant Arabidopsis thaliana has identified the principle photoreceptor for phototropism, phot1, as well as the major auxin transporters. Despite extensive efforts, how the photoreceptor regulates auxin transport so as to establish differential growth is still poorly understood, as is whether this process is conserved between monocots and dicots. Here, we introduce a new approach to the study of Arabidopsis phototropism in the absence of developmental events associated with seedling photomorphogenesis. In doing so, we show that the proximity of light perception and differential growth is conserved between monocots and dicots: in both plant types, differential growth is a consequence of lateral auxin movements across the shoot apex. Moreover, we identify two auxin transporters, PIN3 and ABCB19, that contribute to these movements, the latter serving to prime lateral auxin fluxes in the shoot apex. ABCB19 function is regulated by phot1, identifying it as a substrate for this class of photoreceptor kinase.

In silico gene expression analysis in Codonopsis lanceolata root

Expressed sequence tags (ESTs) provide valuable tools that can be used to predict the genes involved in primary and secondary metabolite synthesis. To the best of our knowledge, ESTs have not yet been developed for Codonopsis. lanceolata, and therefore, the EST referenced in this report is the first transcript for C. lanceolata. A cDNA library was constructed using the roots of C. lanceolata plants that were grown in a field. The selected 881 cDNA clones were sequenced and processed with an EST pipeline, resulting in 636 unique sequences, including 517 singletons and 119 contig sequences. Using bioinformatics tools, 81% of the EST sequence was putatively annotated. Data for unique transcripts were mined from biological databases and functionally classified using gene ontology (GO), the Kyoto Encyclopedia of Genes and Genomes Orthology, KEGG pathway maps, and protein family. The GO-based analyses were examined in terms of biotic and abiotic stress response, transport, cellular component organization, biogenesis, and secondary metabolic processes. The KEGG-based analyses of most transcripts were sorted by carbohydrate metabolism, energy metabolism, and biosynthesis of secondary metabolites. Five randomly-selected putative genes were used for an expression study using various stresses such as salt, H(2)O(2), salicylic acid, and methyl jasmonic acid. Mined data were organized in "The Codonopsis EST Database" (www.bioherbs.khu.ac.kr/Codonopsis).

Screening and optimization of pectin lyase and polygalacturonase activity from ginseng pathogen Cylindrocarpon Destructans

Cylindrocarpon destructans isolated from ginseng field was found to produce pectinolytic enzymes. A Taguchi's orthogonal array experimental design was applied to optimize the preliminary production of polygalacturonase (PG) and pectin lyase (PL) using submerged culture condition. This method was applied to evaluate the significant parameters for the production of enzymes. The process variables were pH, pectin concentration, incubation time and temperature. Optimization of process parameters resulted in high levels of enzyme (PG and PL) production after ten days of incubation at a pH of 5.0 at 25°C in the presence of 1.5% pectin. Among different nitrogen sources, urea and peptone showed high production of PG and PL, respectively. The enzyme production and mycelial growth seems to have direct influence on the culture conditions; therefore, at stationary state high enzyme production and mycelial growth were obtained than agitation state. Along with this, optimization of enzyme activity was also determined using various physiological parameters like, temperature, incubation time and pH. Taguchi's data was also analyzed using one step ANOVA statistical method.

Transcript profiling of antioxidant genes during biotic and abiotic stresses in Panax ginseng C. A. Meyer

The regulation of reactive oxygen scavengers against biotic and abiotic conditions were investigated in the seedling of Panax ginseng C. A. Meyer. From the EST library we selected the antioxidant marker genes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), and glutathione synthase (GS). The abiotic chilling, heat, osmotic, oxidative, and wounding stresses and biotic stresses with fungal pathogens were tested against 3-week-grown seedlings. The expression patterns of the genes were analyzed by means of real-time quantitative RT-PCR. The transcriptome result under abiotic stresses showed differential expression and elevated up-regulation of PgSOD, PgGPX, PgGS, and PgAPX, thus it may prove the generation of ROS in ginseng. Whereas, in biotic stress the up-regulation of transcript level merely based on the incompatible interactions. But PgAPX and PgCAT showed no significant change or slight down-regulation of transcript level during pathogen interaction. Thus it may suggest that in ginseng, plant-pathogen interaction triggers defense-related gene transcription via salicylic acid mediated signaling mechanism, and also possess crosstalk signaling networks between abiotic and biotic stress responses.

Differential auxin-transporting activities of PIN-FORMED proteins in Arabidopsis root hair cells

The Arabidopsis (Arabidopsis thaliana) genome includes eight PIN-FORMED (PIN) members that are molecularly diverged. To comparatively examine their differences in auxin-transporting activity and subcellular behaviors, we expressed seven PIN proteins specifically in Arabidopsis root hairs and analyzed their activities in terms of the degree of PIN-mediated root hair inhibition or enhancement and determined their subcellular localization. Expression of six PINs (PIN1-PIN4, PIN7, and PIN8) in root hair cells greatly inhibited root hair growth, most likely by lowering auxin levels in the root hair cell by their auxin efflux activities. The auxin efflux activity of PIN8, which had not been previously demonstrated, was further confirmed using a tobacco (Nicotiana tabacum) cell assay system. In accordance with these results, those PINs were localized in the plasma membrane, where they likely export auxin to the apoplast and formed internal compartments in response to brefeldin A. These six PINs conferred different degrees of root hair inhibition and sensitivities to auxin or auxin transport inhibitors. Conversely, PIN5 mostly localized to internal compartments, and its expression in root hair cells rather slightly stimulated hair growth, implying that PIN5 enhanced internal auxin availability. These results suggest that different PINs behave differentially in catalyzing auxin transport depending upon their molecular activity and subcellular localization in the root hair cell.

Phospholipase A(2) is required for PIN-FORMED protein trafficking to the plasma membrane in the Arabidopsis root

Phospholipase A(2) (PLA(2)), which hydrolyzes a fatty acyl chain of membrane phospholipids, has been implicated in several biological processes in plants. However, its role in intracellular trafficking in plants has yet to be studied. Here, using pharmacological and genetic approaches, the root hair bioassay system, and PIN-FORMED (PIN) auxin efflux transporters as molecular markers, we demonstrate that plant PLA(2)s are required for PIN protein trafficking to the plasma membrane (PM) in the Arabidopsis thaliana root. PLA(2)alpha, a PLA(2) isoform, colocalized with the Golgi marker. Impairments of PLA(2) function by PLA(2)alpha mutation, PLA(2)-RNA interference (RNAi), or PLA(2) inhibitor treatments significantly disrupted the PM localization of PINs, causing internal PIN compartments to form. Conversely, supplementation with lysophosphatidylethanolamine (the PLA(2) hydrolytic product) restored the PM localization of PINs in the pla(2)alpha mutant and the ONO-RS-082-treated seedling. Suppression of PLA(2) activity by the inhibitor promoted accumulation of trans-Golgi network vesicles. Root hair-specific PIN overexpression (PINox) lines grew very short root hairs, most likely due to reduced auxin levels in root hair cells, but PLA(2) inhibitor treatments, PLA(2)alpha mutation, or PLA(2)-RNAi restored the root hair growth of PINox lines by disrupting the PM localization of PINs, thus reducing auxin efflux. These results suggest that PLA(2), likely acting in Golgi-related compartments, modulates the trafficking of PIN proteins.

WITHDRAWN: Localization and functional activity of APM1 in root-hair cells and BY-2 cells

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Interactions of PIN and PGP auxin transport mechanisms

Polarized transport of the plant hormone auxin influences multiple growth processes in plants and is regulated by plasma-membrane-localized efflux and uptake carriers. The PGP (P-glycoprotein) ABC transporters (ATP-binding-cassette transporters), PIN (pin-formed) subfamily of major facilitator proteins and members of AUX/LAX families have been shown to independently transport auxin both in planta and in heterologous systems. However, PIN- and PGP-mediated transport in heterologous systems exhibits decreased substrate specificity and inhibitor-sensitivity compared with what is seen in plants and plant cells. To determine whether PIN–PGP interactions enhance transport specificity, we analysed interactions of the representative auxin-transporting PGPs with PIN1 and AUX1 in planta and in heterologous systems. Here, we provide evidence that PINs and PGPs interact and function both independently and co-ordinately to control polar auxin transport and impart transport specificity and directionality. These interactions take place in protein complexes stabilized by PGPs in detergent-resistant microdomains.

Interactions among PIN-FORMED and P-glycoprotein auxin transporters in Arabidopsis

Directional transport of the phytohormone auxin is established primarily at the point of cellular efflux and is required for the establishment and maintenance of plant polarity. Studies in whole plants and heterologous systems indicate that PIN-FORMED (PIN) and P-glycoprotein (PGP) transport proteins mediate the cellular efflux of natural and synthetic auxins. However, aromatic anion transport resulting from PGP and PIN expression in nonplant systems was also found to lack the high level of substrate specificity seen in planta. Furthermore, previous reports that PGP19 stabilizes PIN1 on the plasma membrane suggested that PIN-PGP interactions might regulate polar auxin efflux. Here, we show that PGP1 and PGP19 colocalized with PIN1 in the shoot apex in Arabidopsis thaliana and with PIN1 and PIN2 in root tissues. Specific PGP-PIN interactions were seen in yeast two-hybrid and coimmunoprecipitation assays. PIN-PGP interactions appeared to enhance transport activity and, to a greater extent, substrate/inhibitor specificities when coexpressed in heterologous systems. By contrast, no interactions between PGPs and the AUXIN1 influx carrier were observed. Phenotypes of pin and pgp mutants suggest discrete functional roles in auxin transport, but pin pgp mutants exhibited phenotypes that are both additive and synergistic. These results suggest that PINs and PGPs characterize coordinated, independent auxin transport mechanisms but also function interactively in a tissue-specific manner.

Immunophilin-like TWISTED DWARF1 modulates auxin efflux activities of Arabidopsis P-glycoproteins

The immunophilin-like protein TWISTED DWARF1 (TWD1/FKBP42) has been shown to physically interact with the multidrug resistance/P-glycoprotein (PGP) ATP-binding cassette transporters PGP1 and PGP19 (MDR1). Overlapping phenotypes of pgp1/pgp19 and twd1 mutant plants suggested a positive regulatory role of TWD1 in PGP-mediated export of the plant hormone auxin, which controls plant development. Here, we provide evidence at the cellular and plant levels that TWD1 controls PGP-mediated auxin transport. twd1 and pgp1/pgp19 cells showed greatly reduced export of the native auxin indole-3-acetic acid (IAA). Constitutive overexpression of PGP1 and PGP19, but not TWD1, enhanced auxin export. Coexpression of TWD1 and PGP1 in yeast and mammalian cells verified the specificity of the regulatory effect. Employing an IAA-specific microelectrode demonstrated that IAA influx in the root elongation zone was perturbed and apically shifted in pgp1/pgp19 and twd1 roots. Mature roots of pgp1/pgp19 and twd1 plants revealed elevated levels of free IAA, which seemed to account for agravitropic root behavior. Our data suggest a novel mode of PGP regulation via FK506-binding protein-like immunophilins, implicating possible alternative strategies to overcome multidrug resistance.

PIN proteins perform a rate-limiting function in cellular auxin efflux

Intercellular flow of the phytohormone auxin underpins multiple developmental processes in plants. Plant-specific pin-formed (PIN) proteins and several phosphoglycoprotein (PGP) transporters are crucial factors in auxin transport-related development, yet the molecular function of PINs remains unknown. Here, we show that PINs mediate auxin efflux from mammalian and yeast cells without needing additional plant-specific factors. Conditional gain-of-function alleles and quantitative measurements of auxin accumulation in Arabidopsis and tobacco cultured cells revealed that the action of PINs in auxin efflux is distinct from PGP, rate-limiting, specific to auxins, and sensitive to auxin transport inhibitors. This suggests a direct involvement of PINs in catalyzing cellular auxin efflux.

PGP4, an ATP binding cassette P-glycoprotein, catalyzes auxin transport in Arabidopsis thaliana roots

Members of the ABC (for ATP binding cassette) superfamily of integral membrane transporters function in cellular detoxification, cell-to-cell signaling, and channel regulation. More recently, members of the multidrug resistance P-glycoprotein (MDR/PGP) subfamily of ABC transporters have been shown to function in the transport of the phytohormone auxin in both monocots and dicots. Here, we report that the Arabidopsis thaliana MDR/PGP PGP4 functions in the basipetal redirection of auxin from the root tip. Reporter gene studies showed that PGP4 was strongly expressed in root cap and epidermal cells. PGP4 exhibits apolar plasma membrane localization in the root cap and polar localization in tissues above. Root gravitropic bending and elongation as well as lateral root formation were reduced in pgp4 mutants compared with the wild type. pgp4 exhibited reduced basipetal auxin transport in roots and a small decrease in shoot-to-root transport consistent with a partial loss of the redirective auxin sink in the root. Seedlings overexpressing PGP4 exhibited increased shoot-to-root auxin transport. Heterologous expression of PGP4 in mammalian cells resulted in 1-N-naphthylthalamic acid-reversible net uptake of [3H]indole-3-acetic acid. These results indicate that PGP4 functions primarily in the uptake of redirected or newly synthesized auxin in epidermal root cells.

PGP4, an ATP binding cassette P-glycoprotein, catalyzes auxin transport in Arabidopsis thaliana roots

Members of the ABC (for ATP binding cassette) superfamily of integral membrane transporters function in cellular detoxification, cell-to-cell signaling, and channel regulation. More recently, members of the multidrug resistance P-glycoprotein (MDR/PGP) subfamily of ABC transporters have been shown to function in the transport of the phytohormone auxin in both monocots and dicots. Here, we report that the Arabidopsis thaliana MDR/PGP PGP4 functions in the basipetal redirection of auxin from the root tip. Reporter gene studies showed that PGP4 was strongly expressed in root cap and epidermal cells. PGP4 exhibits apolar plasma membrane localization in the root cap and polar localization in tissues above. Root gravitropic bending and elongation as well as lateral root formation were reduced in pgp4 mutants compared with the wild type. pgp4 exhibited reduced basipetal auxin transport in roots and a small decrease in shoot-to-root transport consistent with a partial loss of the redirective auxin sink in the root. Seedlings overexpressing PGP4 exhibited increased shoot-to-root auxin transport. Heterologous expression of PGP4 in mammalian cells resulted in 1-N-naphthylthalamic acid-reversible net uptake of [3H]indole-3-acetic acid. These results indicate that PGP4 functions primarily in the uptake of redirected or newly synthesized auxin in epidermal root cells.

Cellular efflux of auxin catalyzed by the Arabidopsis MDR/PGP transporter AtPGP1

Directional transport of the phytohormone auxin is required for the establishment and maintenance of plant polarity, but the underlying molecular mechanisms have not been fully elucidated. Plant homologs of human multiple drug resistance/P-glycoproteins (MDR/PGPs) have been implicated in auxin transport, as defects in MDR1 (AtPGP19) and AtPGP1 result in reductions of growth and auxin transport in Arabidopsis (atpgp1, atpgp19), maize (brachytic2) and sorghum (dwarf3). Here we examine the localization, activity, substrate specificity and inhibitor sensitivity of AtPGP1. AtPGP1 exhibits non-polar plasma membrane localization at the shoot and root apices, as well as polar localization above the root apex. Protoplasts from Arabidopsis pgp1 leaf mesophyll cells exhibit reduced efflux of natural and synthetic auxins with reduced sensitivity to auxin efflux inhibitors. Expression of AtPGP1 in yeast and in the standard mammalian expression system used to analyze human MDR-type proteins results in enhanced efflux of indole-3-acetic acid (IAA) and the synthetic auxin 1-naphthalene acetic acid (1-NAA), but not the inactive auxin 2-NAA. AtPGP1-mediated efflux is sensitive to auxin efflux and ABC transporter inhibitors. As is seen in planta, AtPGP1 also appears to mediate some efflux of IAA oxidative breakdown products associated with apical sites of high auxin accumulation. However, unlike what is seen in planta, some additional transport of the benzoic acid is observed in yeast and mammalian cells expressing AtPGP1, suggesting that other factors present in plant tissues confer enhanced auxin specificity to PGP-mediated transport.

Immunoelectron microscopic localization of partially purified antigens in adult Paragonimus iloktsuenesis

An immunoelectron microscopy employing immunogold labeling method was performed to detect tissue origin of D1 fraction (D1A) among 5 antigenic protein fractions partially purified by DEAE-anion exchange chromatography from water-soluble crude antigen (PIWA) of adult Paragonimus iloktsuenensis. Immune reactions of adult worm tissues with rabbit serum immunoglobulin immunized with crude antigen (PI-Ig) and D1 antigen (D1-Ig), as well as rat serum immunoglobulin infected with P. iloktsuenensis were observed. D1A showed strong antigenicity in the intestinal epithelium of the worms during the early infection period of 2-4 weeks after infection. The vitellaria also showed stronger antigenicity than the other tissue sites in immune reaction of tissues against all immunoglobulins from 4 to 33 weeks after vitelline development. Therefore, it is suggested that D1A was mainly originated from the intestinal epithelial tissues before the development of vitelline gland of the parasites. Immuno-reactivity of two immunoglobulins (PI-Ig, D1-Ig) was significantly different in intestinal epithelial cytoplasmic protrusions (CP) and intestinal epithelial secretory granules (SG). In the experimental group with D1-Ig, gold particles were labeled significantly in CP than in SG when compared to the PI-Ig group. Thus, the major antigenic materials in D1 antigen having a strong antigenicity in the early infection period was considered to be originated from the intestinal epithelial tissue.

Molecular identification of Paragonimus ohirai and P. westermani from Anhui Province, China

Nucleotide sequences of the internal transcribed spacer 2 (ITS2) region were determined from seven adults of species Paragonimus collected from Jinde and Xiuning Counties, Anhui Province, China. Among these, the nucleotide sequence obtained from one Paragonimus adult (Jinde County) was identical to the ITS2 sequence of P. ohirai previously reported. In order to confirm the result, partial regions of mitochondrial cytochrome C oxidase I (COI) and NADH dehydrogenase 1 (ND1) from the putative P. ohirai sample were further sequenced. They showed a high level of similarity with those of P. ohirai, COI (99.7%) and ND1 (99.5%), supporting the result obtained from the ITS2. In addition to this, we designed P. ohirai- and P. westermani-specific primers (BDW and BD2OH) from ITS2 to identify P. westermani and P. ohirai easily and rapidly. After testing utility of the primers, they were applied to identify seven unidentified Paragonimus samples collected from Jinde and Xiuning Counties, China. All the examined samples showed P. westermani band pattern, and it was reconfirmed by sequencing their ITS2 regions that they are P. westermani. This result indicates that the two newly designed specific primers could be quite helpful for easily identifying P. westermani and P. ohirai, that most of Paragonimus in Jinde and Xiuning Counties consist of P. westermani, and that P. ohirai exists in Jinde County with minority.

[Ultrastructural antigenic localization in Paragonimus iloktsuenensis during developmental stage by immunogold labeling method]

Antigenic localization in Paragonimus iloktsuenensis worm tissues (tegument, intestine and vitelline gland) in different developmental stages of 2 weeks, 3 weeks, 4 weeks, 5 weeks and 33 weeks from albino rats (Sprague-Dawley) infected with P. iloktsuenensis was observed by electron microscopy. These worm tissues of different developmental stage of P. iloktsuenensis was observed on electromicrograph by immunogold labeling method using P. iloktsuenensis infected rat serum of 10 weeks. Antigenic localization was demonstrated as labeling of gold particles in tissues on electronmicrograph. In tegument, gold particles were labeled on tegumental tissue, generally more numerous on secretory granules in tegumental syncytium 2 weeks than those on the other elder developmental stages, but there was a little variation in antigenicity according to individual worm tissue. In general, antigenicity in tegumental tissue was not strong (gold particles: 0.1-5/1 microns 2). In intestine, a large number of gold particles (15-18/1 microns 2) were labeled in intestinal epithelium. Gold particles were concentrated especially on secretory granules in cytoplasm, and gold particles were labeled not only in cytoplasmic protrusions, but also in intestinal luminal contents. Intensity of labeling of gold particles was not correlated with developmental stage of worms. In vitelline gland, a large number of gold particles were labeled on vitelline globules. The gold particles in vitelline globules (8-11/1 microns 2) were concentrated in protoplasm among segmental globules.

[ELISA of rat sera infected with Paragonimus iloktsuenensis]

Enzyme-linked immunosorbent assay (ELISA) of paragonimiasis iloktsuenensis rat sera was performed using crude antigens of Paragonimus iloktsuenensis (PIA), P. westermani (PWA) and Clonorchis sinensis (CSA). Three crude antigens (PIA, PWA, CSA) were prepared to saline homogenated supernatants of whole adult worms. Infected rat sera were obtained biweekly from the albino rats fed 50-80 metacercariae of P. iloktsuenensis through gastric catheter. Experimental groups were divided into 4 groups: GI (controls), GII, GIII and GIV according to 1-7 worms as GII, 10-19 worms as GIII and 22-40 worms as GIV, respectively. In ELISA, the mean OD values of each group for the homologous antigen (PIA) were increased significantly compared to the control sera at the 4th week of infection. With the progress of duration of infection, the mean OD values of infected sera of GII & GIV continuously increased up to the 12th week (last week), but in GIII the mean OD value increased until the 10th week. No significance was noted among the infection dose groups (GII, GIII and GIV), after the 6th week of infection. Also, the OD values of all infected rats did not show any proportional relationships to the number of worms recovered. In brief, the antibody productivity of individual rats were strongly different. The rat sera infected with P. iloktsuenensis cross-reacted with those infected with P. westermani or C. sinensis, as identified by OD values.

[Studies on the immunodiagnosis of rabbit clonorchiasis II. Immunoaffinity purification of whole worm antigen and characterization of egg, metacercaria and adult antigens of Clonorchis sinensis]

The sensitivity and specificity of crude and affinity-purified antigens of Clonorchis sinensis obtained from the infected rabbits were studied. Stage-specific antigenic proteins from the eggs, metacercariae and adult worms were characterized by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunosorbent assay (ELISA) The results were as follows: The antibody-binding antigen (ABA) purified from whole worm crude antigen (WWA) by CNBr-activated Sepharose 4B affinity chromatography made 4 specific bands against rabbit anti-sera on Ouchterlony gel diffusion plate, while WWA made 7 bands. Major WWA protein bands by SDS-PAGE were found at 16,300-18,500 and 28,000-29,000 daltons, while major ABA protein bands were at 18,000-21,000 and 29,000-31,000 daltons. The reactivity of ABA with rabbit anti-sera in ELISA was remarkably less sensitive than that of WWA. Molecular weights of egg antigen (EGA), metacercarial antigen (MEA) and adult worm antigen (WWA) of C. sinensis ranged from 15,000-200,000 daltons, 15,000-100,000 daltons and 11,000-80,000 daltons, respectively. Major WWA proteins consisted mainly of polypeptide bands of low molecular weight, less than 31,000 daltons, while those of EGA and MEA consisted of higher molecular weights than 30,000 daltons. The ELISA reactivities of WWA to rabbit anti-sera were remarkably greater than those of MEA. EGA showed negative reaction throughout the experiments. WWA showed higher optical density (O.D.) than 1.0, when reacted with rabbit anti-sera obtained at 4-6 weeks after the infection. In the rabbit anti-sera later than 12 weeks after the infection, the O.D. reacting with WWA showed a plateau without variation. MEA showed relatively low O.D. values (<0.6), when reacted with anti-sera from lightly infected groups throughout the experiments, although there were some weak positive cases (O.D.>0.6) in heavily infected groups. MEA reacted with rabbit anti-sera showed negative results on Ouchterlony gel diffusion plates. Summarizing the above results, it is suggested that the whole worm antigen prepared from the adult worms of C. sinensis is most highly antigenic. However, this antigen might reveal cross reactions with other trematodes such as Paragonimus westermani, therefore, purification of antigenic proteins from the crude antigen is essential to increase the sensitivity and specificity for the immunodiagnosis of clonorchiasis.

[ELISA of paragonimiasis in cat by crude and purified antigens of Paragonimus westermani]

Enzyme-linked immunosorbent assay (ELISA) using crude and affinity-purified antigens of adult worms of Paragonimus westermani was performed for infected cat sera with different worm burden, from preinfection to 18th week after infection. Crude antigen was used with supernatant of homogenated worms by freezing-thawing method, and the supernate was centrifuged for l hour at 10,000 rpm at 4C. Affinity-purified antigen (antibody-bound antigen) was prepared from fractions (bound and unbound) of crude antigen by affinity chromatography on CNBr-activated sepharose 4B, and IgG as a ligand was prepared from paragonimiasis cat serum (6 months infected) obtained by ammonium sulfate (40-45 per cent saturated) precipitation method. By SDS-PAGE, crude antigen showed 22 polypeptide fractions while purified antigen showed 4 fractions: 36, 400, 34,700,27,600 and 11,500 in molecular weights. All cats were divided into five groups(G1-G5) by different worm burdens. The mean of recovered worms (+/-SD) and the number of cats in each group are as follows:G1, 2 worms(0) and 4 cats; G2, 4.75(+/-0.66) and eight; G3, 10.75(+/-1.92) and four; G4, 25.20(+/-3.43) and five; G5, 48(+/-12.63) and five cats. The results were summarized as follows: The antibody levels(OD value) increased by worm burden in G1 to G4 generally. However, individual antibody levels were not exactly related with worm burden in all groups, especially there was a wide difference in G4 and G5. These results suggested that the worm burden in G4 (about 20 - 30 worms) is enough to produce antibody maximum in cats of 2~3 kg weight. The antibody levels increased significantly (p<0.05) compared to control sera at the 3rd week in G1 and G2, at the 2nd week in G3, and at the 1st week in G4 and G5. Especially in the 4th week, OD value increased more in G1(p<0.001) and in G2 to G5(p<0.01). In the pattern of antibody levels by ELISA in each group, OD in G1 increased to the 18th week continuously, in G2 OD was maintained same after the 16th week, but in G3 it decresed after the 16th week, and it was maintained same in G4 and G5 after the 14th week. The antibody levels by ELISA with the affinity-purified antigen were higher than those with crude antigen in all groups generally. Especially, the difference of OD values between two antigens was larger from the 4th to the 10th week. In G1 and G2 OD with purified antigen was higher than that with crude one to the 18th week. It was also higher in G3 than that with crude antigen to the 16th week and OD of G4 and G5 were higher before the 14th week than that with crude antigen, however became lower at the 16th week. Consequently, the antibody level in ELISA with affinity-purified antigen was more sensitive at the early weeks after infection and in light infection groups than that with crude antigen.

[Comparison Of Agar-Gel Diffusion Tests, Counterimmunoelectrophoresis And Enzyme-Linked Immunosorbent Assay In The Sera Of Skin Test Positives For Paragonimiasis]

Agar-gel diffusion test (AGD), counterimmunoelectrophoresis (CIEP) and enzyme-linked immunosorbent assay(ELISA) were examined with the sera of skin test positives for paragonimiasis. The crude antigen(Paragonimus whole worm extracts: protein concentration, 7.56mg/ml) and human sera were used in AGD and CIEP. And in ELISA test, diluted antigen with 1:40,000 of crude antigen and diluted sera with 1:100, 1:200 were used in the test. The positive identical ratio between AGD and CIEP reactions is 98 % and negative identical ratio is 100 %. One or three precipitin bands are observed in AGD. One to seven precipitin bands are also revealed in CIEP. Especially, deeply stained bands are observed in CIEP than those of AGD. The positive identical ratios between AGD and ELISA tests are 96 % in 1:100 diluted sera, and 94 % in 1:200 diluted sera. But the negative identical ratios between AGD and ELISA tests are 97 % and 99 % respectively in 1:100 and 1:200 diluted sera. The positive identical ratios between CIEP and ELISA tests are 98 % and 96 % respectively in 1:100 and 1:200 diluted sera, but also 97 % and 99 % in 1:100 and 1:200. Control sera, such as clonorchiasis, amoebiasis and toxoplasmosis, revealed all negatives with Paragonimus antigen in AGD, CIEP and ELISA tests. By above results, ELISA was most sensitive, next CIEP and AGD. But AGD test appears to be more useful when used to crude antigen without cross reaction with other parasitic infections. CIEP test is basically equal in terms of precipitin reaction, but CIEP is able to be detected more sensitively and rapidly though less simple in handiwork than AGD. Consequently, three methods for immunological tests of paragonimiasis have good correlations with one another. Also, each of these has both merits and demerits in immunological test for paragonimiasis. But the ELISA test was proved to be the most sensitive and convenient tool for mass screening test, especially in case of using purified antigen.