安蕨属的分类与分布

1849年,捷克人Presl根据菲律宾产的一种蕨类植物Anisocampium cumingia-num Presl,建立了安蕨属Anisocapium Presl,几十年来未被各国植物学家(如Baker、Beddom、Makino、C.Christensen、Christ、Nakai、秦仁昌、Devol、Ohwi和Tagawa)所承认。1940年,Tard.-Blot et C.Chr.编写《印度支那植物通志》(Fl.Gen.Indo-Chine)时接受了安蕨属的概念。1947年,美国人Copeland研究东南亚蕨类植物时,也肯定了安蕨属是一个自然分类群。以后,     

海南岛叉蕨科植物的增补与修订

发现滇桂三相蕨Ataxipteris dianguiensis W. M. Chu & H. G. Zhou和多形叉蕨Tecataria polymorpha (Wall. ex Hook.) Copel.为海南新分布, 并为滇桂三相蕨指定了后选模式,讨论了燕尾叉蕨T. simonsii (Baker) Ching和中型叉蕨T. media Ching的异同,澄清了三叉蕨T. subtriphylla (Hook. & Arn.) Copel.和多形叉蕨的形态变异,把云南产狭基叉蕨T. polymorpha var. subcuneata Ching & Chu H. Wang处理为多形叉蕨的异名。至此,海南产叉蕨科植物为8属20种。     

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.     

中国铁角蕨科铁角蕨属一新记录杂交种——东方铁角蕨

该研究报道了采自山东省泰安市泰山的铁角蕨科铁角蕨属一中国新记录植物——东方铁角蕨(Asplenium×akaishiense Otsuka),并对其形态特征进行了描述。该物种形态介于过山蕨(A. ruprechtii Sa. Kurata)与细茎铁角蕨(A. tenuicaule Hayata)之间,可能是二者的自然杂交种。     

江西省膜蕨科一新记录属——毛边蕨属

在调查九连山自然保护区蕨类植物资源时,发现江西省蕨类植物新记录属、种各1个,即毛边蕨属(Didymoglossum Desv.)和单叶假脉蕨[Didymoglossum sublimbatum (Müller Berol.) Ebihara&K. Iwats.],并讨论其植物地理学意义。     

直立介蕨是假蹄盖蕨属的成员

对直立介蕨Dryoathyrium erectum (Z. R. Wang) W. M. Chu &; Z. R. Wang与介蕨属Dryoathyrium、假蹄盖蕨属Athyriopsis的叶、毛、孢子囊群和孢子的形态进行了比较研究。直立介蕨叶轴和羽轴上的沟槽不明显、具有单列细胞的节状毛、孢子囊群有双生一脉, 以及孢子的形态等特征与假蹄盖蕨属植物相似。结合叶绿体DNA trnL-F区序列分析结果, 所有形态及分子资料均表明该种植物应属于假蹄盖蕨属, 应恢复其原名直立假蹄盖蕨Athyriopsis erectum Z. R. Wang。     

山东对囊蕨属(蹄盖蕨科)植物孢粉学研究及其在分类上的意义

采用扫描电镜对山东分布的8种对囊蕨属(Deparia)植物进行孢粉学观察。研究结果表明:在中国对对囊蕨属(Deparia Hook.& Grev.)蹄盖蕨科(Athyriaceae)新分类系统首次进行孢子形态亚显微结构研究;该属孢子形态圆肾形,左右对称,具周壁,其周壁纹饰在种内稳定,种间区别显著;为建立假蹄盖蕨亚属(Subgen.1.Athyriopsis)和蛾眉蕨亚属(Subgen.2.Lunathyrium )提供孢粉学依据;依据山东蛾眉蕨和东北蛾眉蕨孢壁纹饰的显著差异,山东蛾眉蕨应为一个独立的物种,不宜并入东北蛾眉蕨,建议恢复山东蛾眉蕨在植物分类学上的种级地位,依照对囊蕨属新分类系统,山东蛾眉蕨(Lunathyrium shandongense)新组合为中华山东对囊蕨(D.sinoshandongensis)。该研究不仅为对囊蕨属孢粉学积累了新的资料,也为近缘种的分类鉴定提供了孢粉学依据。因此对囊蕨属孢子形态研究,在该属孢粉学、分类学及系统演化上都具有重要意义。     

山东假瘤蕨与金鸡脚假瘤蕨的孢子形态研究

采用扫描电镜对山东假瘤蕨(Phymatopsis shandongensis J.X.Li et C.Y.Wang)和金鸡脚假瘤蕨(P.hastata(Thunb.)Pic.Serm.)正常发育的成熟孢子进行了系统地观察研究。结果显示,前者孢壁纹饰属粗糙型,后者孢壁纹饰属粗刺型,两者孢壁纹饰差异显著;孢壁纹饰特征在植物分类中具有重要意义,依据孢壁纹饰,山东假瘤蕨应为一个独立的物种,不宜并入金鸡脚假瘤蕨;建议恢复山东假瘤蕨在植物分类学上的种级地位。本研究还提供了金鸡脚假瘤蕨孢子形态特征;补充了假瘤蕨属的扫描电镜孢壁纹饰新资料。研究结果为弄清这两种植物的分类归属提供了孢粉学依据。     

叉蕨科4属5种植物配子体的发育模式及其系统学意义

利用光学显微镜详细观察了叉蕨科(Aspidiaceae)4属5种植物, 即肋毛蕨属(Ctenitis (C. Chr.)C. Chr.)的亮鳞肋毛蕨 (C. subglandulosa (Hance)Ching)和海南肋毛蕨(C. decurrenti-pinnata (Ching)Ching)、轴脉蕨属(Ctenitopsis Ching ex Tard.-Blot et C. Chr.)的轴脉蕨(C. sagenioides (Mett.)Ching)、黄腺羽蕨属(Pleocnemia Presl )的黄腺羽蕨(P. winitti Holtt.)以及叉蕨属(Tectaria Cav.)的剑叶叉蕨(T. leptophylla (C. H. Wright)Ching)的配子体发育过程, 记录了配子体各发育阶段的模式特征, 认为这5种植物的孢子、丝状体、片状体、生长点、翼片、细胞、毛状体和假根等具有稳定的系统学意义。检索结果与该科的经典分类结果基本相似, 并在此基础上编写了各分类群的检索表。本研究为叉蕨科系统学研究积累了详实的配子体形态学资料。     

凤尾蕨属配子体若干系统学特征新考

通过对凤尾蕨属(Pteris L.)8种,即半边旗(P.semipinnata L.)、傅氏凤尾蕨(P.fauriei Hieron.)、阔叶凤尾蕨(P.esquirolii Christ)、三叉凤尾蕨(P.tripartita Sw.)、蜈蚣草(P.vittata L.)、溪边凤尾蕨(P.excelsa Gaud.)、有刺凤尾蕨(P.setuloso-costulata Hayata)、西南凤尾蕨(P.wallichiana Agardh)孢子的人工培养,观察并总结了该属配子体发育各阶段形态特征,并与以往的观察结果进行比较.最终选取孢子萌发型与配子体发育类型等稳定特征作为判断依据,讨论该属与书带蕨科(Vittariaceae)、中国蕨科(Sinopteridaceae)、铁线蕨科(Adiantaceae)等科的亲缘关系.研究认为蕨类配子体生长点上方边缘细胞分布情况多变,不是稳定的系统学特征.而配子体特定部位边缘细胞的外侧壁形态则具有较高的系统学参考价值.     

INTERGENERIC HYBRIDIZATION AMONG FIVE GENERA OF THE FAMILY LESSONIACEAE (PHAEOPHYCEAE) AND EVIDENCE FOR POLYPLOIDY IN A FERTILE PELAGOPHYCUS×MACROCYSTIS HYBRID

Hybridization was attempted by combining gametophytes between intergeneric pairs among the following taxa in the Lessoniaceae: Macrocystis pyrifera ( L.) C. Agardh , M. integrifolia Bory, M. angustifolia Bory , Pelagophycus porra ( Leman) Setch ., Nereocystis luetkeana ( Mert.) Post & Rupr ., Dictyoneurum californicum Rupr ., and Dictyoneuropsis reticulata ( Saud.) Smith. Hybrid sporophytes were produced in some combinations involving Macrocystis × Pelagophycus and Macrocystis × Dictyoneurum, and in all combinations of Dictyoneuropsis × Dictyoneurum. This is the first report of intergeneric hybrids involving Dictyoneurum. Gametophytes of P. porra had 16–24 chromosomes. Gametophytes from a fertile Macrocystis-Pelagophycus hybrid were crossed with Macrocystis and Pelagophycus gametophytes. Hybrid male gametophytes and Pelagophycus female gametophytes produced sporophyte progeny, but hybrid males with Macrocystis females did not. A single hybrid female gametophyte did not produce gametophytes in combination with hybrid males , Pelagophycus males or Macrocystis males. The hybrid gametophytes had approximately 30 chromosomes. It is hypothesized that the hybrid is an alloploid, containing a complete set of Macrocystis and Pelagophycus chromosomes, which may have allowed meiosis and sporogenesis to proceed normally in the hybrid sporophyte found in the sea. Thus, reproductive isolating mechanisms appear to operate at both pre- and postzygotic stages, and both can be overcome in intergeneric hybrids .     

ITS sequence variation and concerted evolution in the natural hybrid species Malus toringoides

The internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) is one of the most used molecular characters in plant systematics. Our previous studies based on morphological analysis and ITS sequence variation suggested that Malus toringoides (Rehd.) Hughes is derived from hybridization between M. transitoria (Batal.) Schneid. and M. kansuensis (Batal.) Schneid. To further understand the variation pattern of ITS sequences in M. toringoides, and to elucidate the evolutionary processes that affect ITS sequence variation after hybridization, we sampled 99 accessions from multiple populations of the hybrid and parental species, and then obtained totally 254 ITS sequences by cloning and sequencing. Our ITS variation data demonstrates three outcomes of ITS repeats after hybrid speciation. ～ 27–41% of M. toringoides have only M. transitoria type ITS sequence, ～ 40–70% have M. transitoria type ITS sequence plus one or two chimeric ITS sequences generated by recombination between parental ITS sequences, and six accessions retain both parental type ITS sequences. The plausible evolutionary processes that created the observed ITS variations were inferred to be the joint actions of recombination, concerted evolution, pseudogenization and backcrossing. Our study provides further understandings of the variation model of ITS repeats after hybridization as well as the evolution of M. toringoides after its hybrid speciation.     

Assortative fertilization and selection at larval stage in the mussels Mytilus edulis and M. galloprovincialis

Assortative mating (prezygotic isolation) and reduced hybrid fitness (postzygotic isolation) are typically invoked to explain the stability of hybrid zones. In the tension zone model, these factors work in opposition to migration, which promotes genetic homogeneity. Many marine animals migrate over long distances through a planktonic larval stage. Therefore, strong reproductive isolation is needed to maintain stable marine hybrid zones. However, surprisingly little is known about mating preferences and hybrid fitness in marine organisms. Smooth-shelled mussels (Mytilus spp.) form a well-known species complex, with hybridization over extensive areas such as the contact zone of M. edulis and M. galloprovincialis around European Atlantic coasts. This paper reports direct experimental evidence of assortative fertilization, hybrid larval inviability, and early heterosis for growth rate in M. edulis and M. galloprovincialis. Four crosses between pure M. edulis and M. galloprovincialis were analyzed with a new polymerase-chain-reaction-based diagnostic marker. Gamete competition between taxa was allowed in two out of the four crosses. Genotype frequencies observed at an early stage (36 h after fertilization) unambiguously revealed assortative fertilization when gamete competition was allowed. A significant reduction in hybrid viability was subsequently observed during the larval stage. At the same stage an antagonistic effect, heterosis, was observed on growth rate. However, even if heterosis is observed in the F1, it is expected to vanish in subsequent hybrid generations. Although specialization for different habitats and asynchronous spawning have been mentioned as factors contributing to the maintenance of the blue mussel hybrid zone in Europe, we argue that assortative fertilization and reduced hybrid fitness are important factors that also contribute to the stabilization of this zone. These results emphasize that multiple factors may act concomitantly in a barrier to gene flow, especially in complex life cycles. Furthermore, they show that assortative mating through gamete preference, as already demonstrated for sea urchins, may play a role in speciation processes taking place in the sea.     

水稻长颖壳突变体的形态发生、解剖结构观察及其遗传鉴定

长颖壳花器官突变体从野生稻(Oryza ntvara Sharma et Shastry)和栽培稻(Oryza sativa subsp.indica Kato)杂交后代材料中获得.该突变体的内外稃变长、呈叶状,且顶端表现不同程度的开裂;每朵颖花的雄蕊l～10枚不等;雌蕊l～3枚不等;子房上柱头l～5个不等;有的颖花形成雄蕊/雌蕊嵌合体;子房处常附有瘤状物;此突变体结实率为1 8.2%;花粉可育率为62.46%.利用扫描电镜观察了该突变体花器官形态发生过程,并经遗传分析鉴定该突变性状由单隐性基因(暂命名为lh)控制.本文讨论了lh基因和以前鉴定的其他突变体基因之间的关系,通过表型分析推测,突变体基因可能影响花器官数目同时具有拟南芥B类基因的部分功能.     

The complete amino acid sequence of barley trypsin inhibitor

The amino acid sequence of barley trypsin inhibitor has been determined. The protein is a single polypeptide consisting of 121 amino acid residues and has Mr = 13,305. No free sulfhydryl groups were detected by Ellman's reagent, which indicates the presence of five disulfide bridges in the molecule. The primary site of interaction with trypsin was tentatively assigned to the arginyl-leucyl residues at positions 33 and 34. On comparison of the sequence of this inhibitor with those of other proteinase inhibitors, we found that the barley trypsin inhibitor could not be classified into any of the established families of proteinase inhibitors (Laskowski, M., Jr., and Kato, I. (1980) Annu. Rev. Biochem. 49, 593-626) and that this inhibitor should represent a new inhibitor family. On the other hand, this trypsin inhibitor showed a considerable similarity to wheat alpha-amylase inhibitor (Kashlan, N., and Richardson, M. (1981) Phytochemistry (Oxf.) 20, 1781-1784) throughout the whole sequence, suggesting a common ancestry for both proteins. This is the first case of a possible evolutionary relationship between two inhibitors directed to totally different enzymes, a proteinase and a glycosidase.     

On the supramolecular organization of gramicidin channels. The elementary conducting unit is a dimer.

The question, whether the conducting channels formed by the linear gramicidins are dimers (as is generally believed) or tetramers (as has been recently proposed [Stark G., M. Strässle, and Z. Takacz. 1986. J. Membr. Biol. 89:23-37; Strässle, M., G. Stark, M. Wilhelm, P. Daumas, F. Heitz, and R. Lazaro. 1989. Biochim. Biophys. Acta. 980:305-314]) has been addressed in single-channel experiments. The experimental approach was based on the ability of electrophysiological (single-channel) experiments to resolve the number of hybrid channel types that could form between gramicidin A or C and O-pyromellityl-gramicidin A or C (in which a pyromellitic acid residue has been esterified to the ethanolamine-OH group [Apell, H.-J., E. Bamberg, H. Alpes, and P. Läuger. 1977. J. Membr. Biol. 31:171-188]). The presence of the bulky, negatively charged pyromellityl group at the channel entrances endows the hybrid channels with characteristically different features and thus facilitates the resolution of the different hybrid channel types. Only two hybrid channel types were detected, indicating that the conducting channels are membrane-spanning dimers. There was likewise no evidence for lateral association between conducting channels and nonconducting monomers. These results can be reconciled with those of Stark et al. (op. cit.) if gramicidin channel formation involves a (slow) folding into beta 6.3-helical monomers followed by the dimerization step.     

Breakdown in the Process of Incipient Speciation in Anopheles gambiae

Understanding genetic causes and effects of speciation in sympatric populations of sexually reproducing eukaryotes is challenging, controversial, and of practical importance for controlling rapidly evolving pests and pathogens. The major African malaria vector mosquito Anopheles gambiae sensu stricto (s.s.) is considered to contain two incipient species with strong reproductive isolation, hybrids between the M and S molecular forms being very rare. Following recent observations of higher proportions of hybrid forms at a few sites in West Africa, we conducted new surveys of 12 sites in four contiguous countries (The Gambia, Senegal, Guinea-Bissau, and Republic of Guinea). Identification and genotyping of 3499 A. gambiae s.s. revealed high frequencies of M/S hybrid forms at each site, ranging from 5 to 42%, and a large spectrum of inbreeding coefficient values from 0.11 to 0.76, spanning most of the range expected between the alternative extremes of panmixia and assortative mating. Year-round sampling over 2 years at one of the sites in The Gambia showed that M/S hybrid forms had similar relative frequencies throughout periods of marked seasonal variation in mosquito breeding and abundance. Genome-wide scans with an Affymetrix high-density single-nucleotide polymorphism (SNP) microarray enabled replicate comparisons of pools of different molecular forms, in three separate populations. These showed strong differentiation between M and S forms only in the pericentromeric region of the X chromosome that contains the molecular form-specific marker locus, with only a few other loci showing minor differences. In the X chromosome, the M/S hybrid forms were more differentiated from M than from S forms, supporting a hypothesis of asymmetric introgression and backcrossing.     

Production and characterization of an interspecific hybrid between leek and garlic

An interspecific hybrid between leek ( Allium ampeloprasum L.) and garlic ( Allium sativum L.) was produced by hybridization using a fertile garlic clone as a pollen donor and an ovary culture. The hybridity was confirmed by chromosome observation (2n = 3 x = 24) and randomly amplified polymorphic DNA (RAPD) analysis. The interspecific hybrid showed a vigorous growth habit, and its foliage was larger than that of the parental species. The bulb of the interspecific hybrid was heavier than that of the parents, containing an intermediate number of cloves. The hybrid could be propagated vegetatively by planting cloves. The odor compounds of garlic, which leek did not have, were detected in the volatiles of the hybrid with a certain concentration. The results of the study suggest the possibility of direct use of an interspecific hybrid between A. ampeloprasum and A. sativum as a new crop.     

Recombinant thermophilic enzymes for trehalose and trehalosyl dextrins production

Two thermophilic and thermostable enzymes, trehalosyl dextrins forming enzyme (TDFE) and trehalose forming enzyme (TFE), able to convert starch and dextrins to ,-trehalose were recently purified and characterized from Sulfolobales [I. Di Lernia, A. Morana, A. Ottombrino, S. Fusco, M. Rossi, M. De Rosa, Extremophiles, 2 (1998) 409; T. Nakada, S. Ikegami, H. Chaen, M. Kubota, S. Fukuda, T. Sugimoto, M. Kurimoto, Y. Tsujisaka, Biosci., Biotechnol., Biochem., 60 (1996) 267; T. Nakada, S. Ikegami, H. Chaen, M. Kubota, S. Fukuda, T. Sugimoto, M. Kurimoto, Y. Tsujisaka, Biosci., Biotechnol., Biochem., 60 (1996) 263; M. Kato, Y. Miura, M. Kettoku, K. Shindo, A. Iwamatsu, K. Kobayashi, Biosci., Biotechnol., Biochem., 60 (1996) 921; M. Kato, Y. Miura, M. Kettoku, K. Shindo, A. Iwamatsu, K. Kobayashi, Biosci., Biotechnol., Biochem., 60 (1996) 925]. The first enzyme transforms starch and dextrins to the corresponding trehalosyl derivatives, with an intramolecular transglycosylation process, which converts the glucosidic linkage at the reducing end from -1,4 to -1,1. The second, hydrolyzes the -1,4 linkage adjacent to the -1,1 bond of trehalosyl dextrins, forming trehalose and lower molecular weight dextrins. Herein, we report the cloning and high level expression of the two enzymes of Sulfolobus solfataricus strain MT4 in Escherichia coli using pTrc expression vector. The yield of TDFE and TFE obtained in this expression system was of 180 U/l and of 3630 U/l of medium, respectively.     

Structure and function of a family 10 beta-xylanase chimera of Streptomyces olivaceoviridis E-86 FXYN and Cellulomonas fimi Cex

The catalytic domain of xylanases belonging to glycoside hydrolase family 10 (GH10) can be divided into 22 modules (M1 to M22; Sato, Y., Niimura, Y., Yura, K., and Go, M. (1999) Gene (Amst.) 238, 93-101). Inspection of the crystal structure of a GH10 xylanase from Streptomyces olivaceoviridis E-86 (SoXyn10A) revealed that the catalytic domain of GH10 xylanases can be dissected into two parts, an N-terminal larger region and C-terminal smaller region, by the substrate binding cleft, corresponding to the module border between M14 and M15. It has been suggested that the topology of the substrate binding clefts of GH10 xylanases are not conserved (Charnock, S. J., Spurway, T. D., Xie, H., Beylot, M. H., Virden, R., Warren, R. A. J., Hazlewood, G. P., and Gilbert, H. J. (1998) J. Biol. Chem. 273, 32187-32199). To facilitate a greater understanding of the structure-function relationship of the substrate binding cleft of GH10 xylanases, a chimeric xylanase between SoXyn10A and Xyn10A from Cellulomonas fimi (CfXyn10A) was constructed, and the topology of the hybrid substrate binding cleft established. At the three-dimensional level, SoXyn10A and CfXyn10A appear to possess 5 subsites, with the amino acid residues comprising subsites -3 to +1 being well conserved, although the +2 subsites are quite different. Biochemical analyses of the chimeric enzyme along with SoXyn10A and CfXyn10A indicated that differences in the structure of subsite +2 influence bond cleavage frequencies and the catalytic efficiency of xylooligosaccharide hydrolysis. The hybrid enzyme constructed in this study displays fascinating biochemistry, with an interesting combination of properties from the parent enzymes, resulting in a low production of xylose.