Partial characterization ofAspergillus fumigatus polygalacturonases for the degumming of natural fibers

Summary Aspergillus fumigatus strain 4, cultured on citrus pectin as the sole carbon source, produced polygalacturonases whose activity was optimum at 65°C and pH 3.5–4.5. The enzymes presented a bimodal thermostability for 10 min, but not 60 min, of incubation. Polygalacturonases showed pH stability between 3.0 to 9.0. The enzymes were stable when stored at 4–6°C for 90 days, but their activity was reduced by 24% when they were stored at 26–30°C. Orange pulp was the best pectic carbon source tested for the production of pectinases capable of retting ramie fibers. The reutilization of these enzymes was possible, suggesting the viability of industrial use of pectinases for degumming ramie fibers.     

Morphological and physiological changes of ramie (Boehmeria nivea L. Gaud) in response to drought stress and GA3 treatment

Ramie (Boehmeria nivea L. Gaud) fibers extracted from the stem bast is one of the most important natural fibers. Ramie growth is severely hindered by drought stress but is promoted by gibberellins (GAs). In order to investigate ramie morphological and physiological responses to drought stress and GA₃ treatment, four groups of potted ramie (severe drought stress (DS), severe drought stress and spraying with GA₃ (DS + GA₃), normal watering and spraying with GA₃ (control + GA₃), and normal watering as a control) were tested. The result showed that, comparing with the ramie growing under well watering condition, a decrease in chlorophyll a (Chl a) and carotenoid and an increase in proline and soluble sugar contents were commonly observed in drought-stressed and GA₃-treated ramie. Different responses of the stem morphological traits, fiber yield, and seven physiological characteristics (relative water content, the activities of POD, SOD, and CAT enzymes, the contents of Chl b, endogenous GAs and MDA) were observed between drought-stressed and GA₃-treated plants. When the ramie suffering drought stress was sprayed with GA₃ (in (DS + GA₃) group), the responses of some physiological traits (POD, SOD, CAT, MDA, and endogenous GAs) and morphological traits (stem shape and fiber yield) to drought stress disappeared completely or partially, and the plant presented similar characteristics of well-watered ramie in these traits. These results suggested that the application of exogenous GA₃ can improve the drought tolerance of ramie.     

RETRACTED ARTICLE: Transgenic ramie [<Emphasis Type="Italic">Boehmeria nivea</Emphasis> (L.) Gaud.]: factors affecting the efficiency of <Emphasis Type="Italic">Agrobacterium</Emphasis><Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transformation and regeneration

In the present study, an efficient Agrobacterium-mediated gene transformation system was developed for ramie [Boehmeria nivea (L.) Gaud.] based on the examinations of several factors affecting plant transformation efficiency. The effects of Agrobacterium cell density, acetosyringone, co-cultivation temperature, co-cultivation duration, co-cultivation photoperiod and pH on stable transformation were evaluated. Agrobacterium at a concentration of OD = 0.5–0.8 improved the efficiency of transformation. Concentration of acetosyringone at 50 mg/L during co-cultivation significantly increased transformation efficiency. Co-cultivation at 20°C, in comparison to 15, 25 and 28°C, consistently resulted in higher transformation frequencies. A relatively short co-cultivation duration (3 days) was optimal for ramie transformation. Co-cultivation medium at pH 5.9 and co-cultivation in darkness both improved the transformation efficiencies of ramie. An overall scheme for producing transgenic ramie is presented, through which an average transformation rate from 10.5 to 24.7% in five ramie varieties was obtained. Stable expression and integration of the transgenes were confirmed by histochemical GUS assay, kanamycin painting assay, PCR and Southern blotting. This optimized transformation system should be employed for efficient Agrobacterium-mediated transformation of ramie. An erratum to this article can be found at     

Large-scale degumming of ramie fibre using a newly isolated <Emphasis Type="Italic">Bacillus pumilus</Emphasis> DKS1 with high pectate lyase activity

A combined (enzymatic and chemical) process using a Bacillus pumilus strain (DKS1), isolated from the soil, was used to degum ramie bast fibres. After 24 h of incubation with the isolated pectinolytic strain using a low-cost medium, the weight loss of the ramie fibre was found to be 25% under small scale. High activity of pectate lyase was detected in the culture supernatants; 400 kg of ramie fibres was degummed with 24% weight loss in large-scale degumming under field conditions. No cellulase activity was found. Microbial intervention followed by mild (0.1%) alkali treatment showed high percentage of weight loss from the ramie fibre. Bacterial degumming followed by chemical treatment resulted in an increase of single fibre tenacity (cN/tex) by more than 20.81% as compared to non-degummed (decorticated) fibre samples. Scanning electron micrographs (SEM) and fluorescence microscope showed that after Bacillus pumilus DKS1 treatment the surface of the decorticated ramie fibre becomes very smooth. These results indicate the process provides an economical and eco-friendly method for the small scale as well as large-scale degumming of decorticated ramie fibre. This study has great relevance to the textile as well as paper industry.     

In vitro plant regeneration from seedling-derived explants of ramie [Boehmeria nivea (L.) Gaud]

Ramie [Boehmeria nivea (L.) Gaud] is one of the most important perennial fiber crops in China. In vitro tissue culture of ramie could serve as an important means for its improvement through genetic transformation. To improve the regeneration capacity of ramie, the effects on plant regeneration of donor plant age, basal medium, plant growth regulators, and culture conditions were evaluated using explants derived from the cotyledon, hypocotyl, leaf, petiole, and stem of ramie seedlings. Cotyledons and hypocotyls excised from 4-d-old seedlings and leaves and petioles and stems from 15-d-old seedlings were optimal explants. The highest regeneration efficiency was obtained on Murashige and Skoog salts with Gamborg’s B₅ vitamins basal medium containing 2.27 μM thidiazuron (TDZ) and 0.054 μM naphthaleneacetic acid (NAA) for the five explant types tested. A photoperiod of 16:8 h (light/dark) was found to be superior than continuous darkness for regeneration of ramie using TDZ. The regenerated shoots were transferred to hormone-free medium for shoot elongation and successfully rooted on half-strength Murashige and Skoog supplemented with 0.134 μM NAA. The rooted plantlets with four to five leaves were transplanted to greenhouse for further growth.     

A novel cottong ovule culture: Induction, growth, and characterization of submerged cotton fibers (Gossypium hirsutum L.)

Summary The growth of submerged cotton (Gossypium hirsutum L.) fibers from cultured ovules has been investigated. The results indicate that exogenous plant hormone levels regulate the induction of submerged fiber growth. The age of ovules at induction is also important. Cell diameter, wall thickness, and cell length of submerged fibers were measured and compared with air-grown fibers and fibers grown in vivo (produced by cotton plants grown in the greenhouse). Various cellwall thickening patterns were observed among submerged fibers, while only one predominant cell-wall deposition pattern was produced in air-grown fibers and in fibers produced in vivo. The diameter of submerged fibers was about the same as that of air-grown fibers but about 22% less than that of fibers grown, in vivo. It appears that the secondary cell wall thickenings are initiated earlier in submerged fibers. The cell-wall thickness of submerged fibers, at 41 d post anthesis (DPA), was 51% greater than that of fibers grown in vivo, whereas the cell-wall thickness of air-grown fibers was 42% less than that of fibers produced in vivo. The cell length of submerged fibers was approximately half that of fibers grown in vivo. and the air-grown fiber length was about two-thirds of fibers grown in vivo. The age of ovules at induction affects the outcome of the air-grown fiber-cell length, but does not appear to affect the length of submerged fiber cells. To produce submerged fiber growth, we found that the optimal age of ovules at induction was 0 DPA, and the optimal medium (with a GA₃ of 0.5 μM and an IAA range of 5-20 μM) depends on the time of ovule induction (−2 to+2DPA). We conclude that conditions leading to submerged cotton fiber growth have great potential for (a) direct monitoring of growth and making precise, detailed measurements during fiber growth and development; (b) producing cellulose and fibers in vitro more efficiently than earlier ovule-culture methods; and (c) using these unique cultures to obtain a better understanding of signal transduction and gene expression leading to growth, development, and programmed cell death in the life history of the cotton fiber.     

Quantitative trait loci affecting cotton fiber are linked to the t1 locus in upland cotton

Pilose (T ₁), a dominant marker in upland cotton, has been associated with coarse, short fibers. Pilose was, thereby, considered to be pleiotropic on fiber fineness and length. However, a pilose-expressing line with a fiber of average fineness was recently identified. This finding does not support pleiotropy between T ₁ and fiber traits, but is indicative of linkage between pilose and loci influencing fiber characteristics. To understand the relationship between T ₁ and fiber traits, a pilose line with short, coarse fiber was crossed to two t ₁ lines with standard fiber characteristics. One hundred and forty-nine F₂-derived F₃ lines were developed from one cross, and 60 F₂-derived F₃ lines from the other. Seven fiber traits (elongation, maturity, micronaire reading, perimeter, 2.5% span length, strength, and wall thickness) were measured. Segregation was normal, as indicated by allelic frequencies of 0.5 for T ₁ and t ₁, and segregation ratios of 121 for marker genotypes. The association of homozygous T ₁ lines with fibers of average fineness was again observed. Linkage between T ₁ and loci affecting micronaire, perimeter, 2.5% span length, strength, and wall thickness was found in both populations. Significant additive and non-additive gene effects for each of these traits at the marker locus were found as well. The pilose marker accounted for 10–75% of the phenotypic variation associated with each trait. In conclusion, the t ₁ locus is linked to numerous loci that influence fiber traits, and this linkage has previously been misinterpreted as pleiotropy.     

The vicissitudes of the pacemaker current <Emphasis Type="Italic">I</Emphasis><Subscript>Kdd</Subscript> of cardiac purkinje fibers

Summary The mechanisms underlying the pacemaker current in cardiac tissues is not agreed upon. The pacemaker potential in Purkinje fibers has been attributed to the decay of the potassium current I _Kdd. An alternative proposal is that the hyperpolarization-activated current I _f underlies the pacemaker potential in all cardiac pacemakers. The aim of this review is to retrace the experimental development related to the pacemaker mechanism in Purkinje fibers with reference to findings about the pacemaker mechanism in the SAN as warranted. Experimental data and their interpretation are critically reviewed. Major findings were attributed to K⁺ depletion in narrow extracellular spaces which would result in a time dependent decay of the inward rectifier current I _K1. In turn, this decay would be responsible for a “fake” reversal of the pacemaker current. In order to avoid such a postulated depletion, Ba²⁺ was used to block the decay of I _K1. In the presence of Ba²⁺ the time-dependent current no longer reversed and instead increased with time and more so at potentials as negative as −120 mV. In this regard, the distinct possibility needs to be considered that Ba²⁺ had blocked I _Kdd (and not only I _K1). That indeed this was the case was demonstrated by studying single Purkinje cells in the absence and in the presence of Ba²⁺. In the absence of Ba²⁺, I _Kdd was present in the pacemaker potential range and reversed at E _K. In the presence of Ba²⁺, I _Kdd was blocked and I _f appeared at potentials negative to the pacemaker range. The pacemaker potential behaves in a manner consistent with the underlying I _Kdd but not with I _f. The fact that I _f is activated on hyperpolarization at potential negative to the pacemaker range makes it suitable as a safety factor to prevent the inhibitory action of more negative potentials on pacemaker discharge. It is concluded that the large body of evidence reviewed proves the pacemaker role of I _Kdd (but not of I _f) in Purkinje fibers.     

QTL mapping for fiber yield-related traits by constructing the first genetic linkage map in ramie (Boehmeria nivea L. Gaud)

Ramie fiber extracted from stem bast is one of the most important natural fibers. The fiber yield of ramie is a valuable trait and is decided by several components, including stem number per plant (SN), the fiber yield per stem (FYPS), stem length (SL), stem diameter (SD), and bark thickness (BT). All of these fiber yield-related traits are inherited in a quantitative manner. The genetic basis for these traits is still uncharacterized, which has hindered the improvement of yield traits through selective ramie breeding. In this study, an F₂ population derived from two ramie varieties, Zhongzhu 1 and Qingyezhuma, with striking differences in fiber yield-related traits, was used for cutting propagation and to develop an F₂ agamous line (FAL) population. A genetic linkage map with 132 DNA loci spanning 2,265.1 cM was first constructed. The analysis of quantitative trait locus (QTL) for fiber yield-related traits was performed in ramie for the first time. Finally, a total of 6, 9, 5, 7, and 6 QTLs for FYPS, SL, SN, SD, and BT, respectively, were identified in the FAL population in two environments. Among these 33 QTLs, 9 QTLs were detected in both environments and 24 QTLs exhibited overdominance. The overdominance of these QTLs possibly contributed to the heterosis of these yield-related traits in ramie. Moreover, there were 7 QTL clusters identified. The identification of the QTLs for fiber yield-related traits will be helpful for improving the fiber yield in ramie breeding programs.     

扇脉杓兰和无距虾脊兰的核型分析

为了解扇脉杓兰(Cypripedium japonicum Thunb.)和无距虾脊兰(Calanthe tsoongiana T. Tang et F. T. Wang)的核型,采用根尖压片法对扇脉杓兰和无距虾脊兰的染色体数目和核型进行了研究。结果表明,扇脉杓兰体细胞的染色体数为22,核型公式为2n=2x=22=16m+2sm+2st+2t,染色体相对长度组成为2n=22=2L+6M2+12M1+2S,核不对称系数为60.01%,核型分类为2B型;而无距虾脊兰体细胞的染色体数为40,核型公式为2n=2x=40=28m+10sm+2st,染色体相对长度组成为2n=40=8L+10M2+16M1+6S,核不对称系数为59.84%,核型分类为2B型;两者核型都较为对称。其中,无距虾脊兰的核型为首次报道。这为扇脉杓兰和无距虾脊兰的进化地位和种质保护提供了细胞学证据。     

Mycoflora and fumonisin-producing strains ofFusarium moniliforme in mixed poultry feeds and component raw material

In a survey of the mycoflora and mycotoxins in foods and feeds, 66 samples of mixed poultry feeds and some component raw materials were investigated. Fungal counts ranged from < 10² to 1.3 × 10⁶ CFU/g.Fusarium spp. counts ranged from 10² to 1.0 × 10⁶ CFU/g. TheFusarium spp. strains isolated were screened for their potential to produce fumonisin B₁ (FB₁) and fumonisin B₂ (FB₂) in maize cultures. Samples and maize cultures were analysed for FB₁ and FB₂ using TLC and fluorescamine-derivative HPLC. No fumonisins were detected in the samples (<6 ppm).Fusarium moniliforme was isolated in 59.1% of samples, and 97.4% of the strains produced FB₁ and 79.4% of strains produced FB₂ in maize cultures. Some isolates produced higher FB₁ and FB₂ levels than the reference strainF. moniliforme MRC 826.     

Regulatory mechanism of contraction in the proboscis retractor muscle of a sipunculid worm,Phascolosoma scolops

Summary Regulatory mechanism of contraction in the proboscis retractor muscle of Phascolosoma scolops was studied by physiological measurements and cytochemical electron microscopy. The magnitude of K⁺-contracture was dependent on external Ca²⁺ concentration and the contracture disappeared in Ca²⁺-free solution. The K⁺-contracture was suppressed by application of procaine and Mn²⁺. Caffeine induced contracture even when external Ca²⁺ was absent. Ultrastructural observations of the retractor muscle cells showed the presence of a large number of vesicles (subsarcolemmal vesicles), corresponding to the sarcoplasmic reticulum in vertebrate skeletal muscle, underneath the plasma membrane. For the cytochemical electron microscopy, the muscle fibers were fixed with 1% OsO₄ solution containing 2% K-pyroantimonate. In the relaxed fibers, pyroantimonate precipitates were localized along the inner surface of plasma membrane and in the subsarcolemmal vesicles. In the contracting fibers, the precipitates were uniformly distributed in the myoplasm. The X-ray microanalysis revealed that the precipitates contained Ca. These results suggest that the contractile system is activated by the influx of extracellular Ca²⁺ as well as by the release of Ca²⁺ from the intracellular structures such as the inner surface of the plasma membrane and subsarcolemmal vesicles.     

苎麻转录因子基因BnMYB3的克隆及表达分析

该研究采用RACE技术,从苎麻中克隆到1个MYB转录因子基因(BnMYB3)的全长cDNA序列(GenBank登录号为MF741320.1)。生物信息学分析表明,BnMYB3基因cDNA全长为1 216bp,包括900bp编码区序列,编码含有299个氨基酸的蛋白,其分子量约为33.63kD,理论等电点为9.16;该蛋白质含有2个典型的MYB结构域,属于R2R3-MYB。从苎麻基因组中克隆了BnMYB3基因1 681bp启动子序列,该序列包含ABRE、GARE-motif、CGTCA-motif和TGACG-motif等多个逆境相关的顺式作用元件。实时荧光定量PCR分析表明,BnMYB3为组成型表达基因,在茎和叶中的表达量显著高于根;BnMYB3基因能够响应镉胁迫,且表达量随镉胁迫处理时间和处理浓度的增加而显著上升。     

Effects of CO2 concentrations on the freshwater microalgae, Chlamydomonas reinhardtii, Chlorella pyrenoidosa and Scenedesmus obliquus (Chlorophyta)

In order to investigate the possible impacts of increased atmospheric CO₂ levels on algal growth and photosynthesis, the influence of CO₂ concentration was tested on three planktonic algae (Chlamydomonas reinhardtii, Chlorella pyrenoidosa, and Scenedesmus obliquus). Increased CO₂ concentration enhanced significantly the growth rate of all three species. Specific growth rates reached maximal values at 30, 100, and 60 M CO₂ in C. reinhardtii, C. pyrenoidosa, and S. obliquus, respectively. Such significant enhancement of growth rate with enriched CO₂ was also confirmed at different levels of inorganic N and P, being more profound at limiting levels of N inC. pyrenoidosa and P in S. obliquus. The maximal rates of net photosynthesis, photosynthetic efficiency and light-saturating point increased significantly (p < 0.05) in high-CO₂-grown cells. Elevation of the CO₂ levels in cultures enhanced the photoinhibition of C. reinhardtii, but reduced that of C. pyrenoidosa and S. obliquus when exposed to high photon flux density. The photoinhibited cells recovered to some extent (from 71% to 99%) when placed under dim light or in darkness, with better recovery in high-CO₂-grownC. pyrenoidosa and S. obliquus. Although pH and pCO₂ effects cannot be distinguished from this study, it can be concluded that increased CO₂ concentrations with decreased pH could affect the growth rate and photosynthetic physiology of C. reinhardtii, C. pyrenoidosa, and S. obliquus.     

Identification of sulphate-reducing ectosymbiotic bacteria from anaerobic ciliates using 16S rRNA binding oligonucleotide probes

The identity of ectosymbiotic bacteria of some marine, free-living anacrobic ciliates (Metopus contortus, Caenomorpha levanderi and Parablepharisma sp.) was studied using fluorescent-dye-conjugated oligonucleotides complementary to short sequence elements of 16S ribosomal RNA. The ectosymbiotic bacteria of all species hybridized with a eubacterial probe and those of the two former mentioned species hybridized with a general probe for sulphate-reducing bacteria, but not to a probe specific for Desulfobacter. The results support indirect evidence suggesting that ectosymbiotic bacteria of anaerobic ciliates are sulphate-reducers which depend on host metabolites for substrates.Abbreviations DMSO dimethyl sulfoxide - PBS phosphate-buffered saline, 137 mM NaCl, 2.7 mM KCl, 4.3 mM Na₂HPO₄, 1.4 mM KH₂PO₄, pH: 7.3 - TEAA triethylamonium acetate - 1 x SSC standard sodium citrate buffer, 150 mM NaCl, 15 mM Na₂ citrate, pH: 7.0 - 1 x Denh Denhardts solution, 0.02% ficoll, 0.02% bovine serum albumine, 0.02% polyvinol-pyralidone     

Action and immunoreactivity of neuropeptides in the buccal neuromuscular system of a prosobranch mollusc,Rapana thomasiana

Summary In a prosobranch mollusc, Rapana thomasiana, the catch-relaxing peptide H-Ala-Met-Pro-Met-Leu-Arg-Leu-NH₂ (CARP) was found to depress the contraction of the radula protractor and retractor elicited by electrical stimulations. The action of CARP was in contrast to that of other neuropeptides, H-Phe-Met-Arg-Phe-NH₂ (FMRFamide) and H-Phe-Leu-Arg-Phe-NH₂ (FLRFamide), which enhanced the contraction of the radula protractor and retractor, respectively. By immunohistochemical examinations, FMRFamide-like immunoreactive neurons were found on the rostral side of the right buccal ganglion and the caudal side of the left ganglion, where some CARP-like immunoreactive neurons were also distributed, indicating a possible coexistence of FMRFamide and CARP. FMRFamide- and CARP-like immunoreactivities were also detected in the neuropile of buccal ganglia, radula nerves arising from the ganglia, and nerve fibers in the radula muscles. The present results suggest that FMRFamide- and CARP-like peptides are involved in the regulation of the contraction of the radula muscles.     

Ethoxyzolamide repression of the low photorespiration state in two submersed angiosperms

Net photosynthesis in the submersed angiosperms Myriophyllum spicatum L. and Hydrilla verticillata (L.f.) Royal was inhibited by 21% O₂, but the degree of inhibition was greater for plants in the high than in the low photorespiratory state. Increasing the CO₂ concentration from 50 through 2,500 l l^-1 decreased the O₂ inhibition of the high-photorespiration plants in a competitive manner, but it had no effect on the O₂ inhibition of plants in the low photorespiratory state. Carbonic-anhydrase activity increased by almost threefold with the induction of the low photorespiratory state. Ethoxyzolamide, an inhibitor of carbonic anhydrase, reduced the net photosynthesis of low-photorespiration Myriophyllum and Hydrilla plants by 40%, but their dark respiration was unaffected. This ethoxyzolamide inhibition of net photosynthesis exhibited a competitive response to CO₂ concentration, resulting in a decrease in the apparent affinity of photosynthesis for CO₂. The net photosynthesis of plants in the high photorespiratory state was inhibited only slightly by ethoxyzolamide, and this inhibition was independent of the CO₂ level. Ethoxyzolamide treatment caused an increase in the O₂ inhibition of net photosynthesis of plants in the low photorespiratory state. Ethoxyzolamide increased the low CO₂ compensation points of low-photorespiration Myriophyllum and Hydrilla, but the values for the high-photorespiration plants were unchanged. In comparison, the CO₂ compensation points of the terrestrial plants Sorghum bicolor (C₄), Moricandia arvensis (C₃-C₄ intermediate) and Nicotiana tabacum (C₃) were unaltered by ethoxyzolamide treatment. These data indicate that the low photorespiratory state in Myriophyllum and Hydrilla is repressed by ethoxyzolamide treatment, thus implicating carbonic anhydrase as a component of the photorespiration-reducing mechanism in these plants. The competitive interaction of CO₂ with ethoxyzolamide provides evidence that the low photorespiratory state in submersed angiosperms is the result of some type or types of CO₂ concentrating mechanism. In Myriophyllum it may be via bicarbonate utilization, but in Hydrilla it probably takes the form of an inducible C₄-type system.Abbreviations PEP phosphoenolpyruvate - RuBP ribulose bisphosphate     

The Pinwheel Experiment Revisited

The critical point hypothesis explains the origin of some cardiac arrhythmias, and the bidomain model describes electrical stimulation of the heart. In this paper, the critical point hypothesis is combined with the bidomain model. The result is four new predictions about the pinwheel experiment, a fundamental experiment in cardiac electrophysiology. These are: (1) The duration of the vulnerable period during cathodalS₂stimulation is longer for anS₁wavefront propagating perpendicular to the fibers than for anS₁wavefront propagating parallel to the fibers. (2) For anodalS₂stimulation with theS₁wavefront propagating parallel to the fibers, the vulnerable period splits into two periods with an “invulnerable period” between them. (3) For anodalS₂stimulation with theS₁wavefront propagating perpendicular to the fibers, the vulnerable period consists of only one period. (4) A previously suggested mechanism for the upper limit of vulnerability (S₂is so strong that the entire tissue is depolarized by an amount greater thanS*) is no longer applicable.     

Flagellar apparatus ultrastructure inMesostigma viride (Prasinophyceae)

The ultrastructure of the flagellar apparatus ofMesostigma viride Lauterborn (Prasinophyceae) has been studied in detail with particular reference to absolute configurations, numbering of basal bodies, basal body triplets and flagellar roots. The two basal bodies are interconnected by three connecting fibers (one distal fiber = synistosome, and two proximal fibers). The flagellar apparatus shows 180° rotational symmetry; four microtubular flagellar roots and two system II fibers are present. The microtubular roots represent a 4-6-4-6-system. The left roots (1s, 2s) consist of 4 microtubules, each with the usual 3 over 1 root tubule pattern. Each right root (1d, 2d) is proximally associated with a small, but typical multi-layered structure (MLS). The latter displays several layers corresponding to the S₁ (the spline microtubules: 5–7), and presumably the S₂—S₄ (the lamellate layers) of the MLS of theCharophyceae. At its proximal origin (near the basal bodies) each right root originates with only two microtubules, the other spline microtubules being added more distally. The structural and positional information obtained in this study strongly suggest that one of the right roots (1d) ofMesostigma is homologous to the MLS-root of theCharophyceae and sperm cells of archegoniate land plants. Thus the typical cruciate flagellar root system of the green algae and the unilateral flagellar root system of theCharophyceae and archegoniates share a common ancestry. Some functional and phylogenetic aspects of MLS-roots are discussed.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

免疫荧光法显示贝居腹盾吸虫肌肉神经组织的实验研究

从背角无齿蚌(Anodonta woodiana)围心腔内检获自然感染的贝居腹盾吸虫(Aspidogaster conchicola),根据虫体内睾丸、卵巢、子宫及卵黄腺4种生殖器官的发育程度,将所获虫体分为幼虫组和成虫组,所有虫体用4%甲醛固定后,分别采用鬼笔环肽染色法和乙酰化微管蛋白免疫组织化学法显示贝居腹盾吸虫成虫和幼虫的肌肉纤维和神经纤维,使用激光共聚焦显微镜观察。结果显示,鬼笔环肽荧光染色的贝居腹盾吸虫成虫较幼虫肌肉组织更为发达,口周围、盾盘附着器、子宫末段及阴茎囊肌肉纤维分布较为密集。乙酰化微管蛋白荧光染色的贝居腹盾吸虫成虫较幼虫神经网络更为复杂,在部分生殖器官如子宫末段、阴茎囊和睾丸部位存在神经纤维。双重染色结果显示,该吸虫不同器官上的肌肉纤维分布与神经纤维的分布相互吻合。该结果提示,贝居腹盾吸虫可能通过神经系统对其肌肉活动进行调控。