The chloroplast genome of a chlorophylla+c-containing alga,Odontella sinensis

The chloroplast genome of a marine centric diatom,Odontella sinensis, was cloned and sequenced. The circular genome is 119,704 bp in length (AC=Z67753;). It contains an inverted repeat sequence of 7,725 bp separating two single-copy regions of 38,908 and 65,346 bp, respectively, and 174 genes and open reading frames, of which nine are duplicated within the inverted repeat segments.     

Effect of UV Irradiance on Utilization of Inorganic Nitrogen by the Antarctic Diatom Odontella weissflogii (Janisch) Grunow

Abstract: The impact of UV-B irradiation on unialgal cultures of the temperate marine diatom Odontella sinensis and of the Antarctic Odontella weissflogii was tested under controlled laboratory conditions. Uptake rates of inorganic nitrogen by Odontella sinensis were more affected by UV-B radiation than those of Odontella weissflogii. Utilization of ¹⁵N-ammonium was reduced after 3 h of UV-B exposure. Values of K_m from several marine phytoplankton species were estimated from algae not exposed to UV-B and from those after 3 h of UV-B radiation. Calculation of Lineweaver-Burk plot showed, under UV-B stress, a noncompetitive inhibition for ¹⁵NH⁺₄ uptake and a competitive inhibitory effect for ¹⁵NO^?₃ by Odontella weissflogii. The damage to ¹⁵NH⁺₄ uptake by UV-B was more pronounced under red than blue light; a contradictory result was obtained for ¹⁵NO^?₃ utilization by Odontella weissflogii. Reduction of the pigments by UV-B under white light was dependent on the exposure time; a strong depression of the contents of chlorophyllide a, chlorophyll c, diatoxanthin and the fucoxanthins was found. Contents of the chlorophylls are markedly affected by UV-B under red light whereas the chlorophyll a concentration is enhanced in blue and green light. UV-B exposure in conjunction with blue and green light led to a reduction of the protein content and an increase in the amino acid contents. The pattern of pool sizes of free amino acids varied after UV-B exposure. UV-A irradiance had no effect. The possible targets of UV-B irradiation on the uptake system of inorganic nitrogen are discussed in detail. Adaptation to the environmental conditions, e.g. via synthesis of UV stress proteins or mycosporine-like amino acids, were also considered.     

CELLULAR MOVEMENT IN THE CENTRIC DIATOM ODONTELLA SINENIS1

Cultured, actively growing cells of Odentella sinensis secrete mucilage, forming gelatinous masses; the mucilage can be visualised with Alcian Blue. When examined live with the light microscope, many cells exhibited continuous small shuffing and rocking movements that could last for long periods (30-40 min); the cells, however, were not translocated and remained relatively fixed in position with respect to their neighbours. Ultrastructural examination of these cells showed prominent aggregations of mucilage vesicles, derived from the Golgi bodies, at the base of the labiate processes, each of which is close to an elevation bearing an ocellus. In Ditylum brightwellii, similar aggreations of these vesides were also located at teh labiate processes; this diatom, too, secretes mucilage but does not have ocelli. We conclude that the movements observed in O. sinenisis are an indirect result of active muilage secretion through the labiate process. It has been suggested that the raphe may have evolved from the labiate process; our conclusion, therefore, has phylogenetic implications, suggesting a functional as well as a morphological relationship between the two valve structures.     

Studies on the biochemistry and fine structure of silica shell formation in diatoms

Summary The sequential wall formation in the centric diatom,Ditylum brightwellii (West) Grunow, is described. The silica deposition vesicle is formed by the coalescence of small vesicles. Silicification of the new valve starts from the central labiate process area prior to the completion of cytokinesis, and the developing valve grows in a centrifugal direction. The initiation of the structures on the valve follows the sequence: labiate process, marginal ridge, and rota. A novel labiate process apparatus, which is situated in the cytoplasm close to the developing labiate process, appears prior to the initiation of the labiate process and disappears upon its maturation. Segments of the girdle bands are formed in individual silica deposition vesicles after the valve matures and is exocytosed. Three morphological forms of deposited silica have been determined: thin base layers, microfibrils, and hexagonal columns. The involvement of cytoplasmic structures in the patterning of the siliceous wall is discussed.     

Aberrant valve formation in a centric diatom,Ditylum brightwellii

Summary Interphase cells of the centric diatom,Ditylum brightwellii (West) Grunow, were treated with a microtubule-inhibitor (amiprophosmethyl, 6×10^–7 M); the cells could proceed to divide, but the spindle apparatus in about 25% of the cells was displaced and their two sibling cells has either two nuclei or none. The cells with two nuclei formed a new valve with two labiate processes, instead of one as in normal cells. Most of the cells lacking a nucleus were unable to form a new valve, and of the 2% that did form new valves, all did so without dividing. The valves with two labiate processes were originally formed in two separate silica deposition vesicles (SDVs) and the two embryonic siliceous valves fused when these two expanding SDVs met. Accordingly, both the pattern of perforations and the shape of the marginal ridges on the new valve vary with the distance between the two initiation sites of the two SDVs. Implications of these observations in the evolution of valves in diatoms are discussed and a hypothesis on multiple origins of the valves is proposed.     

Nucleotide sequence of two cDNAs encoding fucoxanthin chlorophyll a/c proteins in the diatom Odontella sinensis

Two cDNA clones encoding fucoxanthin chlorophyll a/c-binding proteins (FCP) in the diatom Odontella sinensis have been cloned and sequenced. The derived amino acid sequences of both clones are identical, comparison of the corresponding nucleic acids reveals differences only in the third codon position, suggesting a recent gene duplication. The derived proteins are similar to the chlorophyll a/b-binding proteins of higher plants. The presequences for plastid import resemble signal sequences for cotranslational import rather than transit peptides of higher plants. They are very similar to the presequences of FCP proteins in the diatom Phaeodactylum, but different from the presequences of the -subunit of CF₀CF₁ of Odontella and the peridinin chlorophyll a binding proteins (PCP) of the dinoflagellate Symbiodinium.Abbreviations CAB chlorophyll a/b-binding protein - FCP fucoxanthin chlorophyll a/c-binding protein - fcp the respective FCP genes - LHC light-harvesting complex - PCP peridinin chlorophyll a-binding protein - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate     

Beiträge zur Systematischen Anatomie derAnthemideae: Die Spaltöffnungsapparate

The subdivision of theAnthemideae into two subtribes purely on the grounds of the presence or absence of receptacular paleae can no longer be maintained. Anatomical data may serve as a basis for a more adequate division of the tribe. This survey of the stomatal apparatus types within theAnthemideae is based on the investigation of 29 species from 15 genera and the evaluation of literature data: Anomocytic stomatal apparatus occur in all species examined, anisocytic at least in all genera investigated by us. We even found representatives of some rare types, such as polo-, helico- or hemiparacytic apparatus, in nearly all species. Diacytic types were not found inOtanthus, Artemisia, Tripleurospermum, Tanacetum corymbosum, and they also appear to be lacking inSantolina andEriocephalus. Paracytic stomatal apparatus and a new type which links paracytic with actinocytic and cyclocytic was discovered inOtanthus maritimus andArtemisia stellerana.

     

Geographical distribution of Polycelis (Seidlia) auriculata in Japan

Polycelis (Seidlia) auriculata is endemic to mountain districts of Japan, from the central part of Honshû to the area of the Daisetsu Mts of Hokkaidô. In northern Japan, it sometimes occurs in cold-water biotopes of lowland areas. The progenitor of P. auriculata appears to have been the oldest immigrant into northern Japan among the Japanese Polycelis species, entering through a northern route as a preglacial faunal element. P. auriculata now shows a discontinious distribution in northern Japan. By virtue of its geographical and vertical distribution, ecological niche, variation in anatomy of the copulatory apparatus, and cytodemes, this species appears to be in the process of transformation.     

Ultrastructural features of megasporogenesis inTorreya nucifera (Taxaceae)

In megasporogenesis ofTorreya nucifera (Taxaceae) more than one product of meiosis can start to germinate, a process previously observed inTaxus. Ultrastructural analysis ofT. nucifera revealed that this behaviour is cytologically determined by the presence of a transfer cell type wall-membrane apparatus and by the presence of uncommonly complex plasmalemmasomes in the megasporocyte. These features may determine a uniform supply of nutrients to the entire megasporocyte cytoplasm, so that after meiosis the germination potential is not restricted to the chalazal megaspore. Even if more than one product of meiosis can originate the female gametophyte in bothTaxus andTorreya, this process involves different ultrastructural aspects in the two species. In conclusion, the extension of the germination potential is a common characteristic to both species but it is most probably the result of some evolutionary convergence.     

Phagomyxa bellerocheae sp. nov. and Phagomyxa odontellae sp. nov., Plasmodiophoromycetes feeding on marine diatoms

The parasitic Plasmodiophoromycetes Phagomyxa bellerocheae sp. nov. and P. odontellae sp. nov. have been found in the North Frisian Wadden Sea; North Sea, feeding on the centric diatoms Bellerochea malleus and Odontella sinensis, respectively. Their structure and development is investigated by light microscopy and compared. The diagnoses are given. The life cycle of P. odontellae takes about a week. Received in revised form: 25 September 2000 Electronic Publication     

Seasonal reversibility of acclimation to irradiance in leaves of common box (Buxus sempervirens L.) in a deciduous forest

Understorey shade plants are seasonally exposed to dramatic changes in light conditions in deciduous forests related with the dynamics of the overstorey leaf phenology. These transitions are commonly followed by changes in herb plant communities, but shade-tolerant evergreen species must be able to adapt to changing light conditions. In this work we checked the photoprotective responses of evergreen species to acclimate to the shady summer environment and reversibly de-acclimate to a more illuminated environment after leaf fall on deciduous overstoreys. For that purpose we have followed the process of light acclimation in leaves of common box (Buxus sempervirens) during the winter to spring transition, which decrease irradiance in the understorey, and conversely during the transition from summer to autumn. Four parameters indicative of the structure and degree of acclimation of the photosynthetic apparatus have been studied: chlorophyll a/b ratio which is supposed to be inversely proportional to the antenna size, α/β-carotene which increases in shade acclimated leaves and the pools of α-tocopherol and xanthophyll cycle pigments (VAZ) which are two of the main photoprotection mechanisms in plants. Among these parameters, chlorophyll a/b ratio and VAZ pool responded finely to changes in irradiance indicating that modifications in the light harvesting size and photoprotective capacity contribute to the continuous acclimation and de-acclimation of long-lived evergreen leaves.     

新疆委陵菜属不同花柱组植物叶表皮微形态结构的研究

利用光学显微镜和扫描电子显微镜,观察了新疆委陵菜属5组不同花柱组10种4变种植物叶表皮的微形态特征,测量统计叶表皮毛的类型、表皮细胞的形状及大小、气孔器的分布及类型、气孔的形状、大小、密度及指数、气孔外拱盖形态及其纹饰等指标。结果显示:新疆委陵菜属10种4变种植物叶的下表皮均有气孔器的分布,形状为长椭圆形、椭圆形、宽椭圆形和近圆形;气孔器的类型多为无规则四细胞型、无规则型、围绕型和辐射型;表皮毛的类型为针状毛、带状柔毛和腺毛;表皮细胞的形状分为不规则形和多边形2种类型。研究表明,新疆委陵菜属植物表皮毛特征、叶片表皮细胞的形状、垂周壁式样、气孔器的形状类型、气孔密度指数及外围蜡质纹饰等存在差异,对属以下等级的划分有重要价值,可作为物种分类及鉴别的依据,同时也为本属一些分类群间的系统关系的探讨提供佐证。     

Genetic diversity and phylogenetic position of the subclass Astomatia (Ciliophora) based on a sampling of six genera from West African oligochaetes (Glossoscolecidae, Megascolecidae), including description of the new genus Paraclausilocola n. gen

To more confidently assess phylogenetic relationships among astome ciliates, we obtained small subunit (SSU) rRNA sequences from nine species distributed in six genera and three families: Almophrya bivacuolata, Eudrilophrya complanata, Metaracoelophrya sp. 1, Metaracoelophrya sp. 2, Metaracoelophrya intermedia, Metaradiophrya sp., Njinella prolifera, Paraclausilocola constricta n. gen., n. sp., and Paraclausilocola elongata n. sp. The two new species in the proposed new clausilocolid genus Paraclausilocola n. gen. are astomes with no attachment apparatus, two files of contractile vacuoles, and an arc-like anterior suture that has differentiations of thigmotactic ciliature on the anterior ends of the left kineties of the upper surface. Phylogenetic analyses were undertaken using neighbor-joining, Bayesian inference, maximum likelihood, and maximum parsimony. The nine species of astomes formed a strongly supported clade, showing the subclass Astomatia to be monophyletic and a weakly supported sister clade to the scuticociliates. There were two strongly supported clades within the astomes. However, genera assigned to the same family were found in different clades, and genera assigned to the same order were found in both clades. Thus, astome taxa appear to be paraphyletic when morphology is used to assign species to genera.     

The nomenclatural status, ontogeny and morphology of Pholidoteuthis massyae (Pfeffer, 1912) new comb (Cephalopoda: Pholidoteuthidae)

Pholidoteuthis is unusual amongst genera of squid in that the mantle is beset with close-packed dermal cushions (scales). Despite frequent reference to species in this genus, considerable systematic confusion surrounds usage of the generic name, erected prematurely given that the same systematic characters apply for the earlier Tetronychoteuthis Pfeffer, 1900, and species attributed to it. The synonymy and ontogenetic morphology of Pholidoteuthis massyae (Pfeffer 1912) new comb., the senior synonym of P. boschmai Adam, 1950, is reported. The relationship between this species and others referred to Tetronychoteuthis, Lepidoteuthis, the Pholidoteuthidae Adam, 1950, Lepidoteuthidae Pfeffer, 1912 and Octopoteuthidae Berry, 1912, is discussed. A conjectural account of the mechanics of mating in P. massyae is provided based on the nature of spermatophore insertion in the female mantle, and modification to the terminal region of the male’s genital apparatus.     

杜鹃花属映山红亚属植物叶表皮显微形态特征及其分类学意义

为澄清映山红亚属(Rhododendron subg. Tsutsusi)内的系统关系问题,该研究选择杜鹃花属映山红亚属37种植物作为对象,其中29种为首次报道,通过扫描电镜观察其叶表皮显微特征。结果表明:(1)气孔器均为无规则型且均在远轴面。(2)根据叶片微形态特征将映山红亚属的种类分为杜鹃型(R. simisii-type)、岭南杜鹃型(R. mariae-type)、皋月杜鹃型(R. indicum-type)、崖壁杜鹃型(R. saxatile-type)及丁香杜鹃型(R. farrerae-type)5种类型。(3)杜鹃型植物的气孔器周边无或具间断的条形突起。(4)岭南杜鹃型植物的气孔器周围有多层条形突起环绕,保卫细胞两极不具T型加厚。(5)皋月杜鹃型植物的叶表皮保卫细胞两极具有T型加厚,与叶状苞亚属(Subg. Therorhodion)叶状苞杜鹃(R. redowskianum)的气孔器特征相似,推测其与叶状苞亚属具有一定的亲缘关系。(6)崖壁杜鹃型植物的叶表皮毛单一,多呈卷曲状,与其他类型有所不同且未见腺体。(7)丁香杜鹃型植物的叶表皮仅有腺体。(8)依据叶表皮微形态特征讨论了一些近缘种类的关系,如倾向于将背绒杜鹃(R. hypoblematosum)和千针叶杜鹃(R. polyraphidoideum)处理为独立的种,支持保留紫薇春(R. naamkwanense var. cryptonerve)作为南昆杜鹃(R. naamkwanense)的变种地位,不支持将腺花杜鹃(R. adenanthum)并入细瘦杜鹃(R. tenue)作异名处理等。该研究结果表明叶表皮显微特征在映山红亚属内物种划分上具有重要价值。     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

An ultrastructural comparison betweenSpermatozopsis andDunaliella (Chlorophyceae)

The ultrastructure of the type species of the genusDunaliella, D. salina, has been reinvestigated in an attempt to clarify the relationships betweenDunaliella andSpermatozopsis. Dunaliella salina differs in the following ultrastructural characters fromSpermatozopsis (as exemplified byS. similis Preisig etMelkonian): presence of a distinctive surface coat covering the plasmalemma; presence of a prominent pyrenoid (with pairs of thylakoids partially entering the pyrenoid matrix); dictyosomes parabasal; endoplasmic reticulum closely underlying the plasmalemma around most of the cell; contractile vacuoles absent; cell form ovoid to elongated and not spirally twisted; mitochondrial profiles near the flagellar apparatus. Differences in the ultrastructure of the flagellar apparatus: basal body angle more or less fixed; distal connecting fibre cross-striated; system II fibre (rhizoplast) present, associated with mitochondrial profile; system I fibre underlying two-stranded microtubular root; mating structure present. These ultrastructural differences justify distinction between the two taxa at generic level. The problematical status of freshwater species ofDunaliella is briefly discussed.     

Encystment Processes and the “Matrioshka-like Stage” in a Moss-dwelling and in a Limnic Species of Eutardigrades (Tardigrada)

Tardigrades have two forms of dormancy, namely cryptobiosis and encystment. The encystment is a form of diapause known for a limited number of species of tardigrades and still little studied. To increase the knowledge on encystment, two species of eutardigrades from Italy have been considered: the moss-dwelling Amphibolus volubilis (Eohypsibiidae), and the limnic Dactylobiotus parthenogeneticus (Murrayidae). Cysts have been collected in nature, or induced under laboratory conditions. In the latter case, it was possible to follow the several steps of encystment processes. Two different types of cyst (“type 1” and “type 2”) have been found in A. volubilis, while in D. parthenogeneticus only one type has been found. In general, the ovoid-shaped cysts are constituted by a series of cuticles surrounding the animals and resemble an onion or a Matrioshka Russian doll. In all three types of cyst, the encystment processes show both common and peculiar traits. Encystment begins with the discharging of the sclerified parts of the buccal-pharyngeal apparatus, as in the molting process, but without the loss of the old cuticle. Then, two or three new cuticles are serially synthesized, according to cyst type. In A. volubilis, the ultrastructure of these new cuticular involucra is similar to that of non-encysted animal cuticles, while in D. parthenogeneticus the ultrastructure of the new cuticular involucra differs from that of non-encysted animal cuticle. A modified buccal-pharyngeal apparatus has been observed both in “type 2” cyst of A. volubilis and in the D. parthenogeneticus cyst.     

Ultrastructure of the motile cells of the prostrate filamentous green algaeProtoderma sarcinoidea andChamaetrichon capsulatum

The biflagellate zoospores ofProtoderma sarcinoidea and the quadriflagellate zoospores ofChamaetrichon capsulatum are each covered by an amorphous, mucous material and a single layer of square scales, and the pyrenoid matrix is traversed by one or more thylakoid membranes. In the flagellar apparatus the basal bodies ofP. sarcinoidea and the upper basal bodies ofC. capsulatum are displaced in the counterclockwise absolute orientation, while the lower basal bodies ofC. capsulatum are directly opposed. Other components of the flagellar apparatus observed in each alga include: cruciately arranged d and s rootlets, each associated with an electron-dense component; simple terminal caps comprised of large and small subunits; a terminal electron-dense mass located near the proximal end of each basal body inP. sarcinoidea and near the upper basal bodies inC. capsulatum; and two rhizoplasts. Components specific to one or the other species include a single accessory basal body inP. sarcinoidea and a fibrous, electron-opaque band that links the upper and the lower basal bodies inC. capsulatum. The flagellar apparatus architecture ofP. sarcinoidea resemblesGayralia oxysperma, while that ofC. capsulatum is similar toTrichosarcina polymorphum andUlothrix species, all of which are included in theUlothrix-group,Ulotrichales, Ulvophyceae.     

不同缺氮营养水平对金色奥杜藻生长及光合生理的影响

采用了Φ6 cm柱状光生物反应器,在不同氮素营养条件(17.6 mmol/L N、8.8 mmol/L N、5.87 mmol/L N、0 mmol/L N)下通气培养硅藻金色奥杜藻[Odontella aurita(Bacillariophyceae;Centricae)],分析探讨藻细胞的光合生理及生长状况与氮素营养水平的关系。结果表明,不同氮素实验组藻细胞达到最大生长的时间明显差异,与对照组(17.6 mmol/L)相比,氮限制(5.87mmol/L N、8.8 mmol/L N)在培养的前期对金色奥杜藻的生长具有促进作用,氮饥饿(0 mmol/L)显著抑制藻细胞生长(P<0.05)。氮限制实验组藻细胞总碳水化合物的含量显著增加(P<0.05),而总蛋白含量明显下降(P<0.05)。藻细胞叶绿素a、c及总类胡萝卜素含量与培养液的氮素营养水平呈正相关。藻细胞最大光合放氧速率Pm随氮浓度下降而降低,呼吸速率Rd呈现相反趋势,PSⅡ最大光能转化效率(Fv/Fm)、实际光能转化效率(Yield)、潜在活性(Fv/Fo)以及相对电子传递效率(ETR)均随氮素限制而显著下降(P<0.05),说明藻细胞的表观光合生理状况与氮素营养水平直接相关。