Nickel hyperaccumulation defends Streptanthus polygaloides (Brassicaceae) against pathogens

The Ni-hyperaccumulating annual, Streptanthus polygaloides, may contain as much as 16,400 ppm Ni (dry weight) in its tissues. The function of Ni hyperaccumulation is not known. We tested the hypothesis that one function of Ni hyperaccumulation in S. polygaloides is defense against pathogens. Growth of pathogenic organisms on Ni-hyperaccumulating plants (averaging 5,630 ppm Ni, produced by growing plants on high-Ni soil) was compared to pathogen growth on nonhyper-accumulating plants (averaging 124 ppm Ni, produced by growing plants on low-Ni soil). Plants containing hyperaccumulated Ni were more slowly infected by a powdery mildew (Erysiphe polygoni) than low-Ni plants. Two strains of the bacterial pathogen Xanthomonas campestris pv. campestris (one a genetically engineered bioluminescent strain) grew in low-Ni plants but not high-Ni plants. Growth of X. campestris pv. campestris was markedly inhibited by Ni concentrations of 400 ppm in artificial media. Growth of the fungus Alternaria brassicicola, which was necrotrophic on S. polygaloides, also was inhibited on high-Ni leaves relative to low-Ni leaves. These results demonstrated negative effects of hyperaccumulated Ni on a taxonomically wide range of pathogenic organisms, supporting the hypothesis that Ni hyperaccumulation defends S. polygaloides against plant pathogens.     

Metal Tolerance and Accumulation Ability of the Ni Hyperaccumulator Streptanthus polygaloides Gray (Brassicaceae)

High concentrations of metals occur in some plant species (termed hyperaccumulators), such as the Ni hyperaccumulator Streptanthus polygaloides. We determined the tolerance of S. polygaloides to, and its accumulation abilities for, six metals (Ni, Zn, Cu, Co, Mn, and Pb). Potting mix concentrations used for all metals ranged from 0 to 1200 μg/g dry weight. For Ni, a treatment of 1600 μg/g was included. For Mn, treatments of 1600, 2000, and 2500 μg/g also were used, and for Pb these concentrations plus 3500 μg/g were included. Germination, plant number per pot, and size at days 30 and 39, number of plants at the end of the experiment (day 49), flower production, and metal concentration in the aboveground biomass were documented. Lead and Ni showed no consistent effects on plant performance, but yielded increased tissue metal concentrations. Streptanthus polygaloides was more sensitive to Co, Cu, and Zn, as ≥ 400 mg/g significantly suppressed plant growth, survival, and flower production. Tissue metal concentrations also were increased to maxima of 1500 μg Co/g, 120 μg Cu/g, and 6000 μg Zn/g. Manganese affected S. polygaloides less markedly, as ≥ 800 mg/kg decreased growth, survival, and flower production. Maximum tissue Mn concentration was 2900 μg/g. We concluded that S. polygaloides would be an appropriate phytoextractor for soils contaminated with Ni or low levels of Co but would not be useful for Cu, Zn, Mn, and Pb.     

Characterization of the Calcium-Binding Contractile Protein Centrin from Tetraselmis striata (Pleurastrophyceae)

ABSTRACT. Centrin is a major protein of the contactile striated flagellar roots of the green alga Tetraselmis striata . We present a newly modified procedure for the preparation of centrin in sufficient quantity and purity to allow for detailed biochemical characterization. We establish that centrin purified by differential solubility, followed by phenyl-Sepharose and DEAE-Sephacel chromatography is identical with the protein extracted directly from striated flagellar roots with regard to molecular weight, isoelectric point, and calcium-dependent behavior in SDS-PAGE. We also compare the biochemical properties of purified centrin with calmodulin isolated from Tetraselmis and calmodulin isolated from mammalian brain. Centrin can be fully distinguished from either algal or mammalian calmodulin on the basis of molecular weight, isoelectric point, calcium-dependent behavior in SDS-PAGE, proteolytic peptide maps, amino acid composition, ability to activate bovine brain phosphodiesterase, and reactivity with specific antibodies.     

Dynamics of Ni-based defence and organic defences in the Ni hyperaccumulator, Streptanthus polygaloides (Brassicaceae)

Plants use chemical defences to reduce damage from herbivores and the effectiveness of these defences can be altered by biotic and abiotic factors, such as herbivory and soil resource availability. Streptanthus polygaloides , a nickel (Ni) hyperaccumulator, possesses both Ni-based defences and organic defences (glucosinolates), but the extent to which these defences interact and respond to environmental conditions is unknown. S. polygaloides plants were grown on high-Ni and low-Ni soil and concentrations of Ni and glucosinolates were compared with those of the congeneric non-hyperaccumulator, S. insignus spp. insignus , grown under the same conditions. Ni contents were highest (4000 μg g⁻¹ dry tissue) in S. polygaloides plants grown on high-Ni soil. Glucosinolate content was significantly higher in S. insignus than in S. polygaloides suggesting that plants defended by Ni produce a lower concentration of organic defences. In a separate experiment, high-Ni S. polygaloides plants were exposed to simulated herbivory or live folivores to determine the inducibility of Ni-based and organic defences. Contents of Ni were not affected by either herbivory treatment, whereas glucosinolate concentrations were >30% higher in damaged plants. We concluded that the Ni-based defence of S. polygaloides is not induced by herbivory.     

Nickel hyperaccumulation as an elemental defense of Streptanthus polygaloides (Brassicaceae): influence of herbivore feeding mode

No study of a single nickel (Ni) hyperaccumulator species has investigated the impact of hyperaccumulation on herbivores representing a variety of feeding modes. Streptanthus polygaloides plants were grown on high- or low-Ni soils and a series of no-choice and choice feeding experiments was conducted using eight arthropod herbivores. Herbivores used were two leaf-chewing folivores (the grasshopper Melanoplus femurrubrum and the lepidopteran Evergestis rimosalis), a dipteran rhizovore (the cabbage maggot Delia radicum), a xylem-feeder (the spittlebug Philaenus spumarius), two phloem-feeders (the aphid, Lipaphis erysimi and the spidermite Trialeurodes vaporariorum) and two cell-disruptors (the bug Lygus lineolaris and the whitefly Tetranychus urticae). Hyperaccumulated Ni significantly decreased survival of the leaf-chewers and rhizovore, and significantly reduced population growth of the whitefly cell-disruptor. However, vascular tissue-feeding insects were unaffected by hyperaccumulated Ni, as was the bug cell-disruptor. We conclude that Ni can defend against tissue-chewing herbivores but is ineffective against vascular tissue-feeding herbivores. The effects of Ni on cell-disruptors varies, as a result of either variation of insect Ni sensitivity or the location of Ni in S. polygaloides cells and tissues.     

Nickel hyperaccumulation by Streptanthus polygaloides protects against the folivore Plutella xylostella (Lepidoptera: Plutellidae)

We determined the effectiveness of Ni as an elemental defence of Streptanthus polygaloides (Brassicaceae) against a crucifer specialist folivore, diamondback moth (DBM), Plutella xylostella. An oviposition experiment used arrays of S. polygaloides grown on Ni-amended (high-Ni) soil interspersed with plants grown on unamended (low-Ni) soil and eggs were allowed to hatch and larvae fed freely among plants in the arrays. We also explored oviposition preference by allowing moths to oviposit on foil sheets coated with high- or low-Ni plant extract. This was followed by an experiment using low-Ni plant extract to which varying amounts of Ni had been added and an experiment using sheets coated with sinigrin (allyl glucosinolate) as an oviposition stimulant. Diamondback moths laid 2.5-fold more eggs on low-Ni plants than on high-Ni plants and larval feeding was greater on low-Ni plants. High-Ni plants grew twice as tall, produced more leaves, and produced almost 3.5-fold more flowers. Low-Ni plants contained more allyl glucosinolate than high-Ni plants and moths preferred to oviposit on foil sheets dipped in low-Ni plant extract. Moths showed no preference when Ni concentration of low-Ni extract was varied and overwhelmingly preferred sinigrin coated sheets. We conclude that Ni hyperaccumulation is an effective elemental defence against this herbivore, increasing plant fitness through a combination of toxicity to DBM larvae and decreased oviposition by adults.     

嗜麦芽假单胞菌hCG结合蛋白抗体制备及其特性研究

用纯化的嗜麦芽假单胞菌（以下简称细菌）ｈＣＧ结合蛋白制备多克隆抗体。间接免疫沉淀实验证明,该抗体能识别细菌ｈＣＧ结合蛋白－［（１２５）~Ⅰ］ｈＣＧ复合物;配体印迹分析及免疫印迹分析发现,该蛋白能与［（１２５）~Ⅰ］ｈＣＧ发生特异的结合,其结合位置与抗体识别位置一致,为７０ｋＤ蛋白带;同时,该抗体不能特异地抑制细菌ｈＣＧ结合蛋白、大鼠睾丸或卵巢组织细胞膜制剂与［（１２５）~Ⅰ］ｈＣＧ结合。     

Streptanthus bracteatus (Brassicaceae), a rare annual woodland forb, thrives in less cover: evidence of a vanished habitat?

One of the challenges of understanding habitat requirements of endangered species is that the remaining populations may not be in optimal habitat, requiring experimentation to determine optimal habitat and to guide management. A better knowledge of its habitat requirements is important for the conservation of Streptanthus bracteatus, a rare annual of central Texas woodlands. The habitat requirements of a rare, declining species like S. bracteatus can also provide insights into anthropogenic habitat degradation and into previous disturbance regimes. We conducted a garden experiment and a transplant experiment to determine the effect of different light environments on the growth and reproduction of S. bracteatus. Higher levels of light improved S. bracteatus performance, especially fecundity. The optimum level of combined canopy and understory cover at the height of a S. bracteatus plant (??0.5?m above ground) was less than 50?%. The remaining populations of S. bracteatus are in sub-optimal habitat because it is not open enough. The results are consistent with the hypothesis that this species was a ??fire-follower.?? The results also support the hypotheses that central Texas woodlands were once more open and that fire played an ecological role in these woodlands, an example of the ecological requirements of a rare species revealing past community structure and dynamics.     

Detection of Methicillin-Resistant Staphylococcus aureus (MRSA) with Antibodies against Synthetic Peptides Derived from Penicillin-Binding Protein 2′

Ten kinds of peptides (21 to 32 amino acids in length) were synthesized based on the reported amino acid sequences of the penicillin-binding protein 2′ (PBP2′) of methicillin-resistant Staphylococcus aureus (MRSA). Antibodies against these synthetic peptides (SPs) were generated by immunizing rabbits. The antibodies raised against all the peptides except for one reacted to PBP2′ of MRSA and to SPs used for immunization but not to any other protein of MRSA or methicillin-susceptible S. aureus (MSSA) tested by ELISA and Western blotting. A sandwich immunoradiometric assay (IRMA) for the detection of PBP2′ was developed using these antibodies. The method could detect PBP2′ extracted from as few as 3 × 10⁴ cells of a clinical MRSA isolate, and a good correlation between cell number and signal radio-count was observed. IRMA was positive for all 51 methicillin-resistant staphylococci isolated from patients, and was negative for all the 28 methicillin-susceptible ones and 19 strains of other bacterial species. IRMA could be a simple and reliable method for MRSA detection in the clinical bacterial laboratory.     

Ten microsatellite loci from Solms-laubachia eurycarpa (Brassicaceae)

Solms-laubachia eurycarpa is a medicinal herb endemic to the Hengduan Mountains region of south-central China. We screened a partial genomic library enriched for microsatellites and characterized 10 polymorphic loci for S. eurycarpa. The number of alleles per locus ranged from five to 15, with an average of 9.6. The observed and expected heterozygosities ranged from 0.2 to 0.725 and from 0.585 to 0.871, respectively. Amplification in closely related taxa was successful for most loci. The results indicate significant potential for the utility of these markers in studying the population genetics of S. eurycarpa and related species.     

Cloning of cDNA Sequences Encoding the Calcium-Binding Protein, Calmodulin, from Barley (Hordeum vulgare L.)

Full- and partial-length cDNAs encoding calmodulin mRNA have been cloned and sequenced from barley (Hordeum vulgare L.). Barley leaf mRNA, size-fractionated in sucrose density gradients, was used to synthesize double-stranded cDNA. The cDNA was cloned in λgt10 and screened with a synthetic, 14-nucleotide oligonucleotide probe, which was designed using the predicted coding sequences of the carboxy termini of spinach and wheat calmodulin proteins. The primary structure of barley calmodulin, predicted from DNA sequencing experiments, consists of 148 amino acids and differs from that of wheat calmodulin in only three positions. In two of the three positions, the amino acid changes are conservative, while the third change consists of an apparent deletion/insertion. The overall nucleotide sequence similarity between the amino acid coding regions of barley and vertebrate calmodulin mRNAs is approximately 77%. However, a region encoding 11 amino acids of the second Ca²⁺-binding domain is very highly conserved at the nucleotide level compared with the rest of the coding sequences (94% sequence identity between barley and chicken calmodulin mRNAs). Genomic Southern blots reveal that barley calmodulin is encoded by a single copy gene. This gene is expressed as a single size class of mRNA in all tissues of 7-day-old barley seedlings. In addition, these analyses indicate that a barley calmodulin cDNA coding region subclone is suitable as a probe for isolating calmodulin genes from other plants.     

Egg-mimics of Streptanthus (Cruciferae) deter oviposition by Pieris sisymbrii (Lepidoptera: Pieridae)

Summary Streptanthus breweri, a serpentine-soil annual mustard, produces pigmented callosities on its upper leaves which are thought to mimic the eggs of the Pierid butterfly Pieris sisymbrii. P. sisymbrii is one of several inflorescence-infructescence-feeding Pierids which assess egg load visually on individual host plants prior to ovipositing. Removal of the egg-mimics from S. breweri plants in situ significantly increases the probability of an oviposition relative to similar, intact plants.     

Chromosome number evolution in the tribeBrassiceae (Brassicaceae): Evidence from isozyme number

Variation in isozyme number was used to assess the evolution of haploid chromosome numbers (n=6–75) and systematic relationships in the tribeBrassiceae, which is believed to be one of the few monophyletic tribes in theBrassicaceae. Ten enzyme systems were surveyed among 108 species in 35 genera of tribeBrassiceae and for 11 species from seven other tribes. The data indicated that taxa with n=7–13 and n=14–18 were similar in isozyme number, suggesting that genera with n=14–18 did not arise from polyploidy (i.e. entire duplication) of the n=7–13 genomes. These results suggest that aneuploidy and/or chromosome fusion/splitting have played a more significant role than polyploidy in the evolution of higher base chromosome numbers in the tribe. The detection of widespread isozyme duplication in the tribe is consistent with reports of extensive gene duplication in theBrassica crop species, and suggests that the common ancestor of the tribe already had undergone a polyploid event, i.e. complete genome duplication, prior to aneuploid divergence. Inheritance studies conducted onSinapis arvensis showed that segregation ratios at seven loci (Fbp-2,Gpi-2,Idh-2,Pgm-2,Pgm-2,Tpi-1,Tpi-1) conformed to those expected under Mendelian inheritance. Isozyme duplications were phylogenetically informative at various taxonomic levels in the tribe. In particular, duplications for cytosolic phosphoglucomutase (Pgm-2,Pgm-2) and plastid triosephosphate isomerase (Tpi-1,Tpi-1) were evident in 33 of the 35 genera examined, supporting the monophyletic status of theBrassiceae with the inclusion ofOrychophragmus and the exclusion of controversial membersCalepina andConringia.     

A new species of Farsetia (Brassicaceae) from Somalia

Farsetia frutkans , sp. nov., from a limestone escarpment of NE Somalia is described and illustrated.     

A new Biscutella (Brassicaceae) species from the western Balearic Islands

A new diploid species, Biscutella ebusitana is described from coastal cliffs of the western Balearic islands. It is related to B. sempervirens L. and B. montana Cav. from which it can be distinguished by a combination of vegetative (shape, size, petiole and hairs of leaves, petiolatc leaves) and reproductive features (shape of inflorescence, calyx indument). Earlier Balearic records of B. frutescens Coss. should be referred to B. ebusitana.     

Antibodies against Toxoplasma gondii in the Pacific bottlenose dolphin (Tursiops aduncus) from the Solomon Islands

Serum samples from 58 Pacific bottlenose dolphins (Tursiops aduncus) from the Solomon Islands were tested for the IgG antibody to Toxoplasma gondii by the latex agglutination test (LAT), enzyme-linked immunosorbent assay (ELISA), and immunoblotting. The ELISA cut-off value was taken as OD > or = 0.276, and the final dilution ratio, recognized as positive, was represented by the end titer. In 25 of 58 samples, no antibody activity was detected by LAT and ELISA. In 8 of 58 samples, anti-T. gondii IgG antibodies were detected by both LAT and ELISA, with titers of greater than 1 : 64 and 1 : 160, respectively. By immunoblotting, the 8 serum samples producing higher titers showed specific antibody IgG binding to several antigens on the T. gondii lane, but not on the Neospora caninum lane. No specific bands were noted on the lanes for either parasite in the 25 serum samples for which no antibody activity was detected. The specific binding of IgG antibodies to T. gondii antigens observed for serum samples producing higher titers suggests that Pacific bottlenose dolphins from the Solomon islands are exposed to T. gondii.     

A new species of Aethionema (Brassicaceae) from the Bulgarian flora

Aethionema rhodopaeum D. Pavlova is described as a new species from the eastern Rhodope Mountains. The plant was found growing only on serpentines, in two localities, at an altitude of approximately 400 m. The localities are typical open habitats with sparsely colonized debris. The plant communities, composed mainly of xerophytes with a mosaic distribution, contain a large number of rare and endemic species for the Bulgarian flora. The new species belongs to the Aethionema saxatile group and is quite close to the species A. saxatile (L.) R. Br., in particular to ssp. creticum and ssp. graecum . The following diagnostic features are given for the new species: inner filament length always greater than half the petal length, lack of teeth of the filaments, longer [2–3(3.5) mm] style than that of A. saxatile subspecies, and dark purple petals. All leaves are broadly elliptical to suborbicular, obtuse, and fleshy. The chromosome number of the new species is 2 n  = 24. The differences between the new species and related taxa are also discussed.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 533–540.     

Functional Characterization of Antibodies against Neisseria gonorrhoeae Opacity Protein Loops

Background

The development of a gonorrhea vaccine is challenged by the lack of correlates of protection. The antigenically variable neisserial opacity (Opa) proteins are expressed during infection and have a semivariable (SV) and highly conserved (4L) loop that could be targeted in a vaccine. Here we compared antibodies to linear (Ab_linear) and cyclic (Ab_cyclic) peptides that correspond to the SV and 4L loops and selected hypervariable (HV₂) loops for surface-binding and protective activity in vitro and in vivo.

Methods/Findings

Ab_{SV cyclic} bound a greater number of different Opa variants than Ab_{SV linear}, including variants that differed by seven amino acids. Antibodies to the 4L peptide did not bind Opa-expressing bacteria. Ab_{SV cyclic} and Ab_{HV2 cyclic}, but not Ab_{SV linear} or Ab_{HV2 linear} agglutinated homologous Opa variants, and Ab_{HV2BD cyclic} but not Ab_{HV2BD linear} blocked the association of OpaB variants with human endocervical cells. Only Ab_{HV2BD linear} were bactericidal against the serum resistant parent strain. Consistent with host restrictions in the complement cascade, the bactericidal activity of Ab_{HV2BD linear} was increased 8-fold when rabbit complement was used. None of the antibodies was protective when administered vaginally to mice. Antibody duration in the vagina was short-lived, however, with <50% of the antibodies recovered 3 hrs post-administration.

Conclusions

We conclude that an SV loop-specific cyclic peptide can be used to induce antibodies that recognize a broad spectrum of antigenically distinct Opa variants and have agglutination abilities. HV₂ loop-specific cyclic peptides elicited antibodies with agglutination and adherence blocking abilities. The use of human complement when testing the bactericidal activity of vaccine-induced antibodies against serum resistant gonococci is also important.     

Antibodies against Discocotyle sagittata (Monogenea) in farmed trout

The relationship between Discocotyle sagittata intensities and host length, weight and specific anti-parasite antibody titres was studied in 3 year-classes of farmed rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta at the end of the annual transmission cycle. Antibody titres were significantly higher in infected farmed fish than in naive controls, indicating that infection elicits immunoglobulin production. No correlation was found between host size and parasite burdens, nor between infection intensities and antibody titres.