To investigate the saponins from whole plants of Lysimachia davurica Ledeb., two new saponins named davuricoside I (compound 1) and E (compound 2) were isolated. Their chemical structures were elucidated as 3β,16α, 28, 29-tetrihydroxy-olean-12-en-3-O-β-D-glucopyranosyl-(1→2)-β-D-glucuronopyranoside (compound 1) and 3β,16α, 29-trihydroxy-13, 28-epoxy-oleanane-3-O-β-D-glucopyranosyl-(1→2)-β-D-glucuronopyranoside (compound 2) on the basis of their one- and two-dimensional nuclear magnetic resonance and mass spectrometry data, and chemical methods. Compound 1 showed significant cytotoxic activity against human A2780 cells.(Author for correspondence.Tel (Fax): 0571 8827 3061; E-mail: tjk@zju.edu.cn)

For more than a century, ecologists have concentrated on competition as a crucial process for community organization. However, more recent experimental investigations have uncovered the striking influence of positive interactions on the organization of plant communities. Complex combinations of competition and positive interactions operating simultaneously among plant species seem to be widespread in nature. In the present paper, we reviewed the mechanism and ecological importance of positive interactions in plant communities, emphasizing the certainties and uncertainties that have made it an attractive area of research. Positive interactions, or facilitation, occur when one species enhances the survival, growth, or richness of another. The importance of facilitation in plant organization increases with abiotic stress and the relative importance of competition decreases. Only by combining plant interactions and the many fields of biology can we fully understand how and when the positive interactions occur.(Author for correspondence. Tel: +86 (0)571 8697 1083; Fax: +86 (0)571 8697 1083; E-mail: wanggx@zju.edu.cn)

A novel mannose-binding agglutinin was purified from bulbs of Zephyranthes candida Herb by extraction, precipitation with 80% (NH4)2SO4, and ion-exchange chromatography on DEAE-Sepharose followed by gel filtration on Sephacryl S-100. The purified Z. candida agglutinin (ZCA) migrated as a single band of 12 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing and non-reducing conditions. The apparent molecular mass of the lectin, as determined by gel filtration chromatography, was 48 kDa. The results indicated that ZCA was composed of four identical subunits of 12 kDa each (homotetrameric nature). The ZCA agglutinated rabbit erythrocytes, Escherichia coli and Saccharomyces cerevisiae cells at concentrations of 0.95, 1.90, and 31.30 μg/mL, respectively. Bioassays indicated that ZCA has a significant effect on wheat aphid survival. Mortality after 7 d was > 90% at 0.26%. A degenerate primer was designed in accordance with the N-terminal partial sequence of purified ZCA. The full-length cDNA was cloned by 3''- and 5''-rapid amplification of cDNA ends. The full-length cDNA had 661 bp and the sequence encoded an open reading frame of 168 amino acids. The mature protein of ZCA includes 109 amino acid residues and the molecular weight of the protein was 12.1 kDa. The result show that the zca gene encodes a protein precursor with a signal peptide, a mature protein, and a C-terminal cleavage amino acids sequence. Molecular modeling of ZCA indicated that its three-dimensional structure strongly resembles that of the snowdrop agglutinin. Blocks’ analysis revealed that the deduced amino acid sequence of ZCA has three functional domains specific for agglutination and three carbohydrate binding boxes (QDNY).(Author for correspondence.E-mails: scuchenfang@hotmail.com and jinkubao@yahoo.com)

A bacterial artificial chromosome (BAC) library containing a large genomic DNA insert is an important tool for genome physical mapping, map-based cloning, and genome sequencing. To isolate genes via a map-based cloning strategy and to perform physical mapping of the cotton genome, a high-quality BAC library containing large cotton DNA inserts is needed. We have developed a BAC library of the restoring line 0-613-2R for isolating the fertility restorer (Rf1) gene and genomic research in cotton (Gossypium hirsutum L.). The BAC library contains 97 825 clones stored in 255 pieces of a 384-well microtiter plate. Random samples of BACs digested with the NotI enzyme indicated that the average insert size is approximately 130 kb, with a range of 80–275 kb, and 95.7% of the BAC clones in the library have an average insert size larger than 100 kb. Based on a cotton genome size of 2 250 Mb, library coverage is 5.7 × haploid genome equivalents. Four clones were selected randomly from the library to determine the stability of the BAC clones. There were no different fingerprints for 0 and 100 generations of each clone digested with NotI and HindIII enzymes. Thus, the stability of a single BAC clone can be sustained at least for 100 generations. Eight simple sequence repeat (SSR) markers flanking the Rf1 gene were chosen to screen the BAC library by pool using PCR method and 25 positive clones were identified with 3.1 positive clones per SSR marker.(Author for correspondence.Tel (Fax): 025 8439 5307; E-mail: cotton@njau.edu.cn)

The low molecular weight (LMW) glutenin subunits account for 40% of wheat gluten protein content by mass and these proteins are considered to significantly affect dough quality characteristics. Five new full-length LMW glutenin genes (designated LMW-5, LMW-7, LMW-42, LMW-58, and LMW-34) were isolated from the Chinese elite wheat cultivar “Xiaoyan 54” by PCR amplification of genomic DNA using a pair of degenerate primers designed from the conserved sequences of the N- and C-terminal regions of published LMW glutenin genes. Deduced amino acid sequence analysis showed that LMW-5 belongs to the LMW-i type genes and that the other four belong to LMW-m type genes. Sequence comparisons revealed that point mutations occasionally occurred in signal peptide and N-terminus domains and often existed in domain III and domain V. Small insertions and deletions are represented in the repetitive domain. There is a stop codon after amino acid position 110 in the repetitive domain of LMW-34, indicating that it is a pseudogene. The other four genes have complete open reading frames and the putative mature regions of these genes were subcloned into pET-30a expression vector and successfully expressed in Escherichia coli. Protein sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that all proteins expressed in E. coli by the four genes could be related to B-group LMW glutenin subunits of wheat.(Author for correspondence.Tel: 025 8439 5311; Fax: 025 8439 5307; E-mail: moelab@njau.edu.cn)

The voltage-dependent anion channel (VDAC) plays an essential role in the permeability of mitochondrial membrane. In the present study, we isolated a novel VDAC gene (brvdac) based on the assembly of expressed sequence tag sequences from Brassica rapa L. and explored its differential expression patterns in growth, tissues, abiotic stress, and stress recovery. Results of a tissue-specific expression study in young seedlings indicated that, of all tissues tested, brvdac expression was the highest in the leaves. Under cold, drought, and salt stresses, brvdac expression showed a transient increase, and then returned to normal levels when the stress was removed. When plants were exposed to heat shock, there was no increase in brvdac expression, whereas during recovery a quick and considerable increase in expression was observed. These observations indicate that dissimilar modulations of brvdac transcription may occur when plant cells encounter heat shock and the other three types of stress. In addition, phylogenetic analysis implied that an earlier duplication of vdac probably occurred before the divergence between monocotyledons and dicotyledons.(Author for correspondence.Tel: 021 6293 2002; Fax: 021 6282 4073; E-mail: kxtang1@yahoo.com or kxtang@sjtu.edu.cn)

Bryopsis hypnoides Lamouroux was regenerated in vitro from the protoplasm squeezed out from wild algae and the regenerated individuals had an advantage over individuals from the wild in terms of growth. Culturing of segments of thalli also showed that segments from the regenerated algae grew better than those from individuals from the wild. The segment that corresponds to a part of a cell, at least a part of the protoplasm, can develop into a mature individual, including rhizoid and thallus, suggesting that a multinucleate alga, such as B. hypnoides, is different from higher plants, whose totipotency is based on an intact cell (or protoplasm). Further cultivation of mature individuals from segments indicated that the organelles in the thallus had two ways in which they could survive when the alga was on the decline: (i) the organelles were transferred into a ball with a gelatinous envelope through a formed pipe and the ball seemed to be capable of being propagated; and (ii) the organelles were aggregated in the thallus and then moved to the outside. An interesting result is that one organelle aggregation located outside the thallus germinated and developed into a mature alga, although most organelle aggregations gradually lost vitality and died. The results of the present study reveal that the aggregation of organelles can regenerate a stronger organism than individuals from the wild owing to the complete exchange of genetic material and may possibly enable organelles to survive in unfavorable surroundings.(Author for correspondence.Tel: 0532 8289 8574; Fax: 0532 8288 0645; E-mail: gcwang@ms.qdio.ac.cn)

Fluoranthene is one of the polynuclear aromatic hydrocarbons with four benzene rings. Because of its toxicity, mutagenicity, and carcinogenicity, fluoranthene is on the black lists of 129 and 68 priority pollutants established by US Environmental Protection Agency and the People’s Republic of China, respectively. In recent years, the amount of fluoranthene in the aquatic environment has been increasing with increases in anthropogenic discharge. Based on the biological investigation of tidal water in the Futian mangrove, Cyclotella caspia was selected as the dominant algal species to determine the toxicity of fluoranthene towards C. caspia alga and to investigate the biodegradation of fluoranthene by C. caspia under pure culture. The toxicity experiment showed that the 96-h EC50 value for fluoranthene was 0.2 mg/mL. Four parameters, namely C. caspia algal growth rate, chlorophyll (Chl) a content, cell morphology, and superoxide dismutase (SOD) activity, were chosen as indices of toxicity and were measured at 6 d (144 h). The results showed that: (i) the toxicity of fluoranthene towards C. caspia alga was obvious; (ii) C. caspia algal growth rate and Chl a content decreased with increasing concentrations of fluoranthene; and (iii) the rate of cell deformation and SOD activity increased with increasing concentrations of fluoranthene. The biodegradation experiment showed that: (i) the rate of physical degradation of fluoranthene was only 5.86%; (ii) the rate of biodegradation of fluoranthene on the 1st and 6th days (i.e. at 24 and 144 h) was approximately 35% and 85%, respectively; and (iii) the biodegradation capability of C. caspia alga towards fluoranthene was high. It is suggested that further investigations on the toxicity of fluoranthene towards algae, as well as on algal biodegradation mechanisms, are of great importance to use C. caspia as a biological treatment species in an organic wastewater treatment system.(Author for correspondence.School of Life Sciences, State Key Laboratory for Biocontrol, Sun Yet-sen (Zhongshan) University, Guangzhou 510275, China Tel.: +86 (0)20 8403 6296; Fax: +86 (0)20 8411 3652; E-mail: ls04@zsu.edu.cn)

In the present study, we investigated the role of gibberellic acid (GA3) and indole acetic acid (IAA) in the gravity response of stems and tension wood formation using two-year-old stems of Fraxinus mandshurica Rupr. var. japonica Maxim seedlings. Forty-five seedlings were used and divided into nine groups that included five seedlings in each group. Seedlings were treated with applications of GA3 alone at concentrations of 2.89 × 10–8 and 2.89 × 10–7 μmol/L, IAA alone at concentrations of 5.71×10–8 and 5.71×10–7 μmol/L, or their combination to the apical bud of the stem using a micropipette. Seedlings were positioned horizontally after the first treatment. The same treatments were repeated six times per week. At the end of the experiment, all seedlings were harvested. Then, stem segments were cut under a light microscope. Application of exogenous GA3 at the higher concentration stimulated the upward bending of stems, whereas exogenous IAA had no effect. A synergistic effect of GA3 and IAA on upward stem bending was observed following application of the two combinations of GA3 and IAA. Moreover, application of exogenous GA3 at the higher dose stimulated wood formation on both the upper and lower sides of the stems, whereas the mixture of GA3 and IAA had a synergistic effect on wood formation in horizontal stems. Application of exogenous IAA alone at the lower concentration (5.71×10–8μ mol/L) or application of a mixture of the higher concentrations of GA3 (2.89 × 10–7 μmol/L) and IAA (5.71×10–7μmol/L) inhibited the development of gelatinous fibers (the G-layer) of tension wood on the upper side of the horizontal stems. The differentiation of gelatinous fibers of tension wood was not inhibited by GA3 when it was applied alone, whereas the development of the gelatinous fibers of tension wood was strongly affected by the application of IAA. The findings of the present study suggest that the development of the G-layer is not related to the dose of GA3, but needs a relatively lower concentration of IAA.(Author for correspondence.Tel: 022 2350 4732; Fax: 022 2350 4732; E-mail: jiangsha@nankai.edu.cn)

Quantifying spatial patterns of species richness and determining the processes that give rise to these patterns are core problems in biodiversity theory. The aim of the present paper was to more accurately detect patterns of vascular species richness at different scales along altitudinal gradients in order to further our understanding of biodiversity patterns and to facilitate studies on relationships between biodiversity and environmental factors. Species richness patterns of total vascular plants species, including trees, shrubs, and herbs, were measured along an altitudinal gradient on one transect on a shady slope in the Dongling Mountains, near Beijing, China. Direct gradient analysis, regression analysis, and geostatistics were applied to describe the spatial patterns of species richness. We found that total vascular species richness did not exhibit a linear pattern of change with altitude, although species groups with different ecological features showed strong elevational patterns different from total species richness. In addition to total vascular plants, analysis of trees, shrubs, and herbs demonstrated remarkable hierarchical structures of species richness with altitude (i.e. patchy structures at small scales and gradients at large scales). Species richness for trees and shrubs had similar spatial characteristics at different scales, but differed from herbs. These results indicated that species groups with similar ecological features exhibit similar biodiversity patterns with altitude, and studies of biodiversity based on species groups with similar ecological properties or life forms would advance our understanding of variations in species diversity. Furthermore, the gradients or trends appeared to be due mainly to local variations in species richness means with altitude. We also found that the range of spatial scale dependencies of species richness for total vascular plants, trees, shrubs, and herbs was relatively large. Thus, to detect the relationships between species richness with environmental factors along altitudinal gradients, it was necessary to quantify the scale dependencies of environmental factors in the sampling design or when establishing non-linear models.(Author for correspondence.Tel: 010 6283 6223; Fax: 010 8259 1781; E-mail: makp@brim.ac.cn)

Zooxanthellae are very important for the coral reef ecosystem. The diversity of coral hosts is high in the South China Sea, but the diversity of zooxanthellae has not yet been investigated. We chose the Zhubi Coral Reef of the Nansha Islands as the region to be surveyed in the present study because it represents a typical tropical coral reef of the South China Sea and we investigated zooxanthellae diversity in 10 host scleractinian coral species using polymerase chain reaction (PCR) of the large subunit rRNA and restriction fragment length polymorphism (RFLP) patterns. Pocillopora verrucosa, Acropora pelifera, Acropora millepora, Fungia fungites, Galaxea fascicularis, and Acropora pruinosa harbor Clade C, Goniastrea aspera harbors Clade D, and Acropora formosa harbors Clades D and C. Therefore, the Clade C is the dominant type in the Zhubi Coral Reef of the Nansha Islands. Furthermore, the results of the present also disprove what has been widely accepted, namely that one coral host harbors only one algal symbiont. The coral-algal symbiosis is flexible, which may be an important mechanism for surviving coral bleaching. Meanwhile, on the basis of the results of the present study, we think that Symbiodinium Clade D may be more tolerant to stress than Symbiodinium Clade C.(Author for correspondence.Tel: 020 8446 0294; Fax: 020 8446 0294; E-mail: coral@scsio.ac.cn)

Two new compounds, 1-(3-methoxy-4-hydroxyphenyl)-3-(3, 5-dimethoxy-4-hydroxyphenyl)-propane (1) and 5, 7, 3''-trimethyoxyflavan-4''-O-β-D-glucopyranoside (2) were isolated from the ethanol extract of the dried aerial parts of Phacellaria compressa Benth., together with 2,3-bis[(4-hydroxy-3,5-dimethoxyphenyl)-methyl]-1,4-butanediol (3), ethyl 3,4,5-trihydroxybenzoate (4), methyl 3, 4, 5-trihydroxybenzoate (5),β-sitosterol (6), 5, 7, 3'', 4''-tetrahydroxyflavan (7), lupeol (8), zhebeiresinol (9), quercetin-3-O-α-L-rhamnopyranoside (10), (+)-catechin (11), betulin (12), β-daucosterol (13), (+)-syringaresinol (14), scopoletin (15), and proximadiol (16). The structures of these compounds were determined by spectral evidence or by comparing them with authentic samples. Compound 9 showed α-amylase inhibitory activity of 57.55% at a concentration of 50 μg/mL.

Investigation of the Mesozoic seed plant Leptostrobus Heer from the Yangcaogou Formation of the Late Triassic and the Yixian Formation of the Early Cretaceous, Liaoning Province, China, provides new insight into its general morphology and geographical distribution. The materials of L. cancer from the Yixian Formation described herein are later than all the past findings of this species and add to the record of L. cancer during the Early Cretaceous. Based on well-preserved specimens, the specific diagnosis is slightly emended and the reconstruction of L. cancer is perfected. The materials from the Yangcaogou Formation of the Late Triassic are placed in L. sphaericus. In addition, we review the history of investigation of the genus Leptostrobus since its establishment in 1876 and discuss the main characteristics of each species.(Author for correspondence.Tel: 010 6283 6436; Fax: 010 6259 3385; E-mail: lics@ibcas.ac.cn)

Agrobacterium rhizogenes Conn. causes hairy root disease in plants. Hairy root-infected A. rhizogenes is characterized by a high growth rate and genetic stability. Hairy root cultures have been proven to be an efficient means of producing secondary metabolites that are normally biosynthesized in roots of differentiated plants. Furthermore, a transgenic root system offers tremendous potential for introducing additional genes along with the Ri plasmid, especially with modified genes, into medicinal plant cells with A. rhizogenes vector systems. The cultures have turned out to be a valuable tool with which to study the biochemical properties and the gene expression profile of metabolic pathways. Moreover, the cultures can be used to elucidate the intermediates and key enzymes involved in the biosynthesis of secondary metabolites. The present article discusses various applications of hairy root cultures in plant genetic engineering and potential problems associated with them.(Author for correspondence.Tel (Fax): 021 5132 2508; E-mail: huzhibi@hotmail.com)