An ultrastructural study of the mature spermatozoid of the fern Asplenium trichomanes L. subsp. trichomanes

 Asplenium trichomanes L. subsp. trichomanes spermatozoids are spirals of about five turns. Keels link the elements of the microtubular ribbon with the plates of the lamellar layer (LL) which are uninterrupted, parallel and curved with an inner angle of about 150°. Electron-opaque filaments connect the microtubules of the multilayered structure (MLS) and the osmiophilic crest, the LL and the MLS-associated mitochondrion and the latter and the plasmalemma. The nucleus occupies the 2.5–3 posterior turns and has an inner honeycomb-shaped chromatin mass and an outer highly condensed chromatin mass with randomly scattered electron-transparent areas. The basal bodies of the ca. 50 flagella are bounded by a reticulum of granular material which forms a plug inside their proximal region; the proximal region of the flagellum has a 9 + 0 pattern. The axoneme has a 9 + 2 pattern. Received: 15 January 1997 / Revision accepted: 1 April 1997     

中国铁角蕨的种下分类学研究

综合运用孢粉学、细胞学、生态学和形态学的证据,处理了中国产铁角蕨Asplenium trichomanes L． 的种下分类问题,将其划分为4个亚种和1个变种：原亚种A．trichomanes L．ssp．trichomanes,喜钙亚种 A．trichomanes L. ssp．inexpectans Lovis,四倍亚种A．trichomanes L．ssp. quadrivalens D．E．Meyer emend． Lovis,粗轴亚种A．trichomanes L．ssp.pachyrachis(Christ)Lovis et Reichst．和哈如变种A．trichomanes L. var．harovii Moore emend．Midle,并提供了它们在中国的分布情况。查阅研究中国科学院植物研究所 (PE)的标本时发现,一些定名为A．trichomanes L．var．centrochinense Christ(华中变种)的模式标本碎片在形态上和倍性上均不同于已知分类群,认为应给予其新种的分类地位。     

A subspecific taxonomic study on Asplenium trichomanes L. from China

With the evidence from palynological, cytological, ecological and morphological data, the subspecific taxonomy of Asplenium trichomanes L. from China is carried out. Four subspecies and one variety, i.e.A. trichomanes L. ssp. trichomanes, A. trichomanes L. ssp. inexpectans Lovis, A. trichomanes L. ssp. quadrivalens D. E. Meyer emend. Lovis, A. trichomanes L. ssp. pachyrachis (Christ) Lovis et Reichst. and A. trichomanes L. var. harovii Moore emend. Midle are recognized from China. The distribution of each subspecies and variety is also presented. Some fragments of a type specimen named as A. trichomanes L. var. centrochinense Christ in PE are found to be different from the known taxa of A. trichomanes L. complex both morphologically andcytologically, and therefore are regarded representing a new species.     

The Asplenium trichomanes complex in East Central Sweden

An investigation of the Asplenium trichomanes complex in some Swedish provinces is presented. The study comprises ssp. trichomanes 2n = 72, ssp. inexpectans 2n = 72, ssp. quadrivalens 2n = 144 and a triploid hybrid 2n = 108. The ssp. inexpectans is reported from Sweden for the first time. It is previously only known from Central and Southern Europe. It was found to be about as common as the other two subspecies occurring in Sweden.     

Some factors affecting the chloroplast replication in the mossPlagiomnium trichomanes

Summary Some factors affecting the chloroplast replication were studied using the leaf cells of the mossPlagiomnium trichomanes. There was a significant positive correlation between chloroplast number per cell and cell volume in leaves of any developmental stage. However, when the detached leaves were cultured on nutrient agar, it was observed that the chloroplast replication occurred without cell enlargement regardless of the developmental stage of leaves. This implies that cell enlargement is not an essential factor for the chloroplast replication, but one of the environmental factors affecting it. Light is essential for the chloroplast replication which response to the light intensity. In the dark, there was little increase in chloroplast number per cell. With a light intensity of 50 lux, the increase rate of chloroplast number per cell was about half of that with 3,000 lux. Day length also affected significantly the chloroplast replication.     

Effects of antibiotics on the chloroplast replication in the mossPlagiomnium trichomanes

Protoplasma - Four morphological processes were observed during the cycle of the chloroplast replication of the mossPlagiomnium trichomanes; spherical to ellipsoidal, ellipsoidal to slight...     

The Role of Light-Induced Membrane Potential Changes in Guttation in Gametophytes of Asplenium trichomanes

Gametophytes of the fern Asplenium trichomanes exhibit guttationwhen illuminated. Membrane potential changes evoked by lightwere measured in the presence of ion channel and proton pumpinhibitors to elucidate the nature of the response and a possiblelink to guttation. Light-induced depolarization was suppressedby the anion channel inhibitors: anthracene-9-carboxylic acidand niflumic acid. Potassium channel blockers: TEA and Ba²⁺caused an increase of the amplitude of light-induced membranepotential changes. Calcium channel inhibitors, La³⁺ Gd³⁺ diltiazem,nifedipine and verapamil had no significant effect on the membranepotential changes. Similarly, proton pump inhibitors, diethylstilbestroland vanadate, had only minor effects on the response. A possiblerole of Cl^– and K⁺ fluxes in light-induced guttation isdiscussed. (Received July 8, 1999; Accepted October 13, 1999)     

Investigations into the Genetic Variation, Population Structure, and Breeding Systems of the Fern Asplenium trichomanes subsp. quadrivalens

The genetic structure of five populations of the tetraploid fern Asplenium trichomanes subsp. quadrivalens in northern Switzerland was analyzed. Asplenium trichomanes subsp. quadrivalens is one of the most common and most widespread ferns in Europe. In this study we have combined genetic investigations, spatial autocorrelation, and breeding experiments to investigate in detail five populations from natural rock faces. Enzyme electrophoresis revealed very low genetic variability within and among the populations. The small amount of variation was partitioned mainly among the localities, indicated by high Fst values up to 0.764. Overall means of the proportion of polymorphic loci (P=0.076), the mean number of alleles per locus (A=1.086), and the mean expected heterozygosity (H=0.018) were low compared with other ferns (e.g., Kirkpatrick et al. 1990). Very few heterozygous individuals were found. Values of the fixation index (F) were high, ranging between 0.732 and 1.000 and indicating substantial inbreeding. Spatial autocorrelation showed different patterns of substructure in populations of A. trichomanes subsp. quadrivalens with a tendency for patches in short distances (up to 1.5 m). The breeding experiments with isolated prothalli and prothalli pairs showed that a mean of 56.4% of the isolated prothalli were successful in sporophyte formation. The highest rate in one population was 83.3%. We conclude that genetic load must be low in A. trichomanes subsp. quadrivalens. Sporophyte formation was statistically more successful in the experiments with gametophyte pairs than in isolates, indicating that additional cross-fertilization occurred. The latter agreed with the occurrence of few heterozygote samples and the small number of multilocus phenotypes found in natural habitats. Asplenium trichomanes subsp. quadrivalens is shown to be a highly inbreeding taxon with the capability of single spore colonization and subsequent founding of new populations. Such features can be hypothesized to have contributed to the postglacial colonization and the widespread distribution of this taxon in Europe.     

Soil preference of populations of genotypes ofAsplenium trichomanes L. andPolypodium vulgare L. in Belgium as related to cation exchange capacity

A number of populations ofPolypodium vulgare L. andAsplenium trichomanes L. were sampled with corresponding soils in Belgium in order to get an idea of their suitability for the investigation of related calcicole and calcifuge taxa. Morphology and cytology enabled us to distinguish the subspecies and the hybrids. Analyses of the soils for pH, CaCO₃, Al and H show that subspecies and hybrids have distinct soil preferences and can be characterised as calcicoles-neutrophile/basiphiles or calcifuge-acidiphiles. Physiological implications of the ecological status of the taxa are discussed in the light of their root cation exchange capacity.     

铁角蕨属4种植物配子体发育的比较研究

以腐叶土为基质培养铁角蕨(Asplenium trichomanes L.)、阿尔泰铁角蕨[A.altajense(Kom.)Grubov]、假大羽铁角蕨(A.pseudolaserpitii folium Ching)和细裂铁角蕨(A.tenui folium D.Don)的孢子,用光学显微镜观察并比较它们的配子体发育过程,以期为铁角蕨属的系统学研究提供基础资料.结果显示,4种铁角蕨属植物配子体均具有:孢子两面型、单裂缝、周壁具褶皱、书带蕨型萌发,成熟原叶体心形,原叶体具有毛状体等共同特征,表明铁角蕨属的演化处于较进化的系统位置,但它们的毛状体形态和细胞数目明显不同,可为属内分系提供依据.研究发现,4种铁角蕨属植物配子体的边缘细胞形状以及假根的形态和数量均有差异,其叶绿体能象单细胞一样进行无丝分裂,强光照射下叶绿体向相邻细胞的侧壁集中等现象.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.