Chromosome and DNA methylation dynamics during meiosis in the autotetraploid Arabidopsis arenosa

Variation in chromosome number due to polyploidy can seriously compromise meiotic stability. In autopolyploids, the presence of more than two homologous chromosomes may result in complex pairing patterns and subsequent anomalous chromosome segregation. In this context, chromocenter, centromeric, telomeric and ribosomal DNA locus topology and DNA methylation patterns were investigated in the natural autotetraploid, Arabidopsis arenosa. The data show that homologous chromosome recognition and association initiates at telomeric domains in premeiotic interphase, followed by quadrivalent pairing of ribosomal 45S RNA gene loci (known as NORs) at leptotene. On the other hand, centromeric regions at early leptotene show pairwise associations rather than associations in fours. These pairwise associations are maintained throughout prophase I, and therefore likely to be related to the diploid-like behavior of A. arenosa chromosomes at metaphase I, where only bivalents are observed. In anthers, both cells at somatic interphase as well as at premeiotic interphase show 5-methylcytosine (5-mC) dispersed throughout the nucleus, contrasting with a preferential co-localization with chromocenters observed in vegetative nuclei. These results show for the first time that nuclear distribution patterns of 5-mC are simultaneously reshuffled in meiocytes and anther somatic cells. During prophase I, 5-mC is detected in extended chromatin fibers and chromocenters but interestingly is excluded from the NORs what correlates with the pairing pattern.     

Chromosome ends and the nuclear envelope at premeiotic interphase in the male grasshopper Brachystola magna by 3-D,E.M. reconstruction

During premeiotic interphase in the male grasshopper Brachystola magna the nucleus is divided into two nuclear envelope bound compartments, one containing the X chromosome and one the autosomes. — The autosomal compartment is characterized by an invaginated nuclear envelope with nuclear pores distributed throughout the envelope. In a polarized region of the cell the pericentric heterochromatic chromocenters are associated with the inner membrane of the envelope invaginations. In this species the chromosomes are telocentric (acrocentric?) and the pericentric heterochromatin marks the proximal chromosome ends. It is concluded that the chromosome ends are attached to the nuclear envelope at premeiotic interphase. — Comparisons are made between the present observations on chromosome arrangements and the nuclear envelope at premeiotic interphase to earlier observations at early meiotic prophase in the same species (Church, 1976). It is concluded that a rearrangement of both the proximal chromosome ends and the nuclear envelope occurs as cells enter meiotic prophase.     

凤仙花花药发育中多糖和脂滴组织化学研究

以不同发育时期的凤仙花花药为实验材料,采用组织化学方法,对花药发育中的结构变化及多糖和脂滴物质分布进行观察。结果表明:(1)凤仙花的花药壁由6层细胞组成,包括1层表皮细胞,2层药室内壁细胞,2层中层细胞和1层绒毡层细胞。其中绒毡层细胞的形态不明显,很难与造孢细胞区分,且在小孢子母细胞时期退化。(2)在小孢子母细胞中出现了一些淀粉粒,但减数分裂后,早期小孢子中的淀粉粒消失,又出现了一些小的脂滴;随着花粉的发育,小孢子形成大液泡,晚期小孢子中的脂滴也消失;小孢子分裂形成二胞花粉后,营养细胞中的大液泡降解、消失,二胞花粉中又开始积累淀粉;接近开花时,成熟花粉中充满细胞质,其中包含了较多的淀粉粒和脂滴。(3)在凤仙花的花药发育中,绒毡层细胞很早退化,为小孢子母细胞和四分体小孢子提供了营养物质;其后的中层细胞退化则为后期花粉发育提供了营养物质。     

The time and duration of the premeiotic inteprhase in microsporocytes ofTrillium kamtschaticum

The time and duration of each phase of the premeiotic interphase were determined in microsporocytes of two clones (S and K clones) ofTrillium kamtschaticum. After collectionTrillium plants were stored at 3 C or 7 C prior to completion of premeiotic mitosis in archesporial cells. For autoradiography, cells were explanted in the presence of³H-thymidine to identify the interval of the premeiotic DNA synthesis. Approximate durations of the G₁, S and G₂ phases for the K clone stored at 3 C were estimated to be 12, 12 and 14 days, respectively. The interval of premeiotic development was markedly different between clones. A high degree of synchrony in meiotic development, which is usually observed within anthers up to late meiotic prophase, was confirmed at the S phase, suggesting that synchrony is established during the G₁ interval.     

天竺桂凋落叶添加对凤仙花生理特性的影响

采用盆栽试验,通过向土壤(每盆8kg)中添加0(CK)、20(L20)、40(L40)和80g·pot-1(L80)天竺桂(Cinnamomum japonicum)凋落叶,模拟其自然分解对凤仙花(Impatiens balsamina)生理特性的影响。结果显示:(1)天竺桂凋落叶处理显著增加了凤仙花现蕾前期和现蕾期叶片H2O2含量,同时显著抑制了凤仙花现蕾前期、现蕾期和盛花期超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性。(2)凋落叶添加处理显著增加了凤仙花现蕾前期抗坏血酸(ASA)含量,但现蕾期和盛花期ASA含量却显著下降。(3)添加凋落物处理显著降低了现蕾前凤仙花叶片MDA含量,但显著增加了现蕾期MDA含量,而盛花期MDA含量在L20、L80处理下显著降低,在L40处理下则显著增加。(4)天竺桂凋落叶添加对可溶性蛋白和可溶性糖两种渗透调节物质含量影响不显著。(5)凋落叶处理显著抑制了凤仙花地径生长和地上生物量积累。(6)天竺桂凋落叶中主要化感物质可能有香豆素、桉叶油醇、肉桂醛、反式石竹烯和松油醇等。研究认为,非酶促活性氧清除系统可能在凤仙花抵御化感物质氧化胁迫过程中发挥着比酶促系统更为重要的作用,其中的ASA在氧化胁迫的早期过程扮演着重要角色;天竺桂凋落叶添加处理所造成的氧化胁迫可能超过了两类活性氧清除系统的清除能力,对凤仙花膜系统造成明显伤害,导致其地径和生物量积累显著降低。     

Beitrag zur Cytotaxonomie der GattungThlaspi

Zusammenfassung Für achtThlaspi-Arten werden Chromosomenzahlen mitgeteilt, davon fürT. bulbosum Sprun. exBoiss., 2 n=14 undT. kotschyanum Boiss. etHohen., 2 n=14 erstmalig. Für sechs weitere Taxa werden bekannte Zahlen bestätigt:T. alpestre L. s. lat., 2 n=14,T. alpinum Crantz, 2 n=14, 28,T. goesingense Halacsy, n=28, 2 n=56,T. kovatsii Heuffel, 2 n=14,T. perfoliatum L., 2 n=42 undT. rotundifolium (L.)Gaud. ssp. cepaeifolium (Wulf.)Rouy etFouc., 2 n=14. Dazu kommen Hinweise systematischer, pflanzengeographischer und ökologischer Natur, u. a. der sichere Nachweis vonT. goesingense für Jugoslawien.

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Summary Chromosome numbers of eightThlaspi-species were counted, the last two for the first time:T. alpestre, 2 n=14;T. alpinum, 2 n=14 and 28;T. goesingense, n=28, 2 n=56;T. kovatsii (=T. avalanum), 2 n=14;T. perfoliatum, 2 n=42:T. rotundifolium ssp.cepaeifolium, 2 n=14;T. bulbosum, 2 n=14 andT. kotschyanum, 2 n=14. There are additional remarks on the taxonomical position, distribution and ecology of these taxa;T. goesingense is verified for Yugoslavia.

     

串叶松香草Giemsa C带和染色中心研究

以Giemsa C带技术处理串叶松香草根尖细胞染色体(2n=14),全部着丝点及第5和第7对染色体短臂端部显稳定的C带,第6对染色体长臂有两条明显的居间带,其他居间带小而不稳定(重复率不高)。间期细胞核染色体呈Rable构型,其着丝点一极最多出现20个染色中心。统计分析表明,靠近着丝点的短臂端带区和居间带区异染色质有易与着丝点区异染色质融合的倾向。分裂中期Giemsa C带数目与间期染色中心数目存在数量对应关系。     

OBSERVATIONS ON PREMEIOCYTES OF WHEAT

Electron microscopic observations of wheat premeiocytes in premeiotic mitosis (PMM) and premeiotic interphase (PMI) are reported. In archesporial cells of columns at last PMM there is a significant increase in activity of endoplasmic reticulum. Characteristic states of chromatin of premeiocyte nuclei in the stages of PMI are illustrated. Changes in the primary walls of PMCs at Stage 1, PMI, precede the formation of callose in Stage 2. In general, callose deposition throughout the PMC column follows the pattern described elsewhere in Sorghum and other Gramineae. The behavior of the plasmalemma during callose synthesis resembles that described elsewhere in Cucurbita. A role for the cell endomembrane system in callose synthesis is suggested. Blebs arising from the inner membrane of the nuclear envelope, described elsewhere in endosperm cells of wheat and by us in wheat PMCs in this report, give rise to vesicles which carry nuclear material into the cell cytoplasm. Differences in this transport mechanism as it appears in the two tissue systems are described.     

Zwei Ausgangskaryotypen bei der Gräser-GattungAira L.

Zusammenfassung Für die Arten der GattungAira L. werden die folgenden Chromosomenzahlen mitgeteilt:A. capillaris Host, 2n=14;A. caryophyllea L., 2n=14 und 28;A. multiculmis Dum., 2n=28;A. praecox L., 2n=14;A. tenorii Guss., 2n=14;A. provincialis Jord., 2n=28 undA. cupaniana Guss., 2n=14. Die Zahlen der letzten drei Arten werden zum erstenmal veröffentlicht.Bei den diploiden Arten kommen zwei unterschiedliche Karyotypen vor: A ist verbreitet, B aufA. praecox beschränkt. Der Karyotyp der tetraploidenA. caryophyllea setzt sich aus A+B zusammen, während es sich beiA. multiculmis um eine Verdoppelung von A handelt. — Über die Verbreitung der Arten und Cytotypen werden einige Hinweise gegeben.

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Two basic karyotypes in the grass genusAira L.

Summary Chromosome numbers of all known species of the genusAira L. are counted:A. capillaris Host, 2n=14;A. caryophyllea L., 2n=14 and 28;A. multiculmis Dum., 2n=28;A. praecox L., 2n=14;A. tenorii Guss., 2n=14;A. provincialis Jord., 2n=28 andA. cupaniana Guss., 2n=14. The numbers of the last three species are published for the first time. Two different karyotypes are found amongst the diploids: A is widespread, B limited toA. praecox. The karyotype of the tetraploidA. caryophyllea can be described as AB, that ofA. multiculmis as AA. — Remarks on the distribution of the species and cytotypes are added.

     

Systematics and karyoevolution inMagnoliidae:Tetrameranthus as compared with otherAnnonaceae genera of the same chromosome number

First generic chromosome counts reveal the base number x=7 for the generaTetrameranthus andRollinia. T. umbellatus from the Peruvian Amazon is diploid (2n=14),T. duckei from Brazil (Manaus) is tetraploid (2n=28). In the NeotropicsRollinia (7 species counted) has developed diploid to octoploid taxa (2n=14, 28, 42, 56). Counts of 7 South AmericanAnnona species are presented for comparison (2n=14, 28). The West AfricanCleistopholis patens has 2n=14. The Asian genusMezettia: 2n=14 and the neotropicalGuatteria tribe: 2n=28 are also revised. A detailed karyomorphological comparison, including karyotypes, banding patterns, condensing behaviour of chromosomes and structure of interphase nuclei reveals that the closely related generaAnnona andRollinia are almost identical in their diploid genomes, whereas the polyploid ones differ in their heterochromatin (=hc) composition and number of NO-chromosomes.Cleistopholis, Mezettia and theGuatteria tribe are karyologically and systematically distinct from each other and fromAnnona/Rollinia. Tetrameranthus as compared with the karyomorphology of about 60 other Annonaceous genera has a very peculiar and unusual karyomorphology which underlines its isolated position. Nuclear structures are almost identical in the African genusUvariopsis (2n = 16) and partly similar in theGuatteria tribe; both also share some morphological similarities and possibly are related. From a comparison ofTetrameranthus with several nuclear types within theMagnoliidae, a new model of chromosome evolution in primitive Angiosperms is suggested. In respect to their eco-morphological differentiation the genera investigated differ strongly from each other.Dedicated to Prof. Dr. K.-H.Rechinger on the occasion of His 80th birthday.     

4-(2′-Carboxyphenyl)-4-oxobutyrate: An obligatory intermediate in lawsone biosynthesis

4-(2′-Carboxyphenyl)-4-oxobutyric acid (6) has been detected in cuttings of Impatiens balsamina. It is labelled under conditions where activity from U-¹⁴C-glutamate is incorporated effectively into lawsone (1). 3-(2′-Carboxyphenyl)-3-oxopropionic acid (7) has also been encountered in the cuttings.     

Fine structure and cytochemistry of the nuclei of the primitive ciliateTracheloraphis crassus (Karyorelictida)

Summary The nuclei ofTracheloraphis crassus were studied using light and electron microscopy combined with Bernhard's RNP staining and pronase digestion. The nuclear apparatus of this species consists of a longitudinal row of 11–43 macronuclei and 4–16 micronuclei. Like in all karyorelictids, the macronuclei are unable to divide and become segregated during cytokinesis; their number is supplemented in every cell cycle by differentiation of several new macronuclei from micronuclei.Each adult macronucleus contains a single compact endonuclear aggregate of several large chromocenters, readily destained with EDTA, and several RNP containing nucleoli. There is continuity between the material of the chromocenters and the decondensed DNP fibrils in the nuclear matrix. The nucleoli contain NORs in the form of fibrillar centers. The endonuclear aggregate includes also groups of RNP granules which are especially resistant to EDTA destaining. A microfibrillar sphere, usually localized at the periphery of the aggregate, contacts one or several nucleoli. The sphere is not bleached with EDTA, and only its periphery becomes digested with pronase. The macronuclear matrix consists of both protein fibrils and pronase-resistant fibrils, the latter being localized at the nuclear periphery.Developing macronuclear primordia contain loose strands of decondensed chromatin; only later they form chromocenters and nucleoli.The micronuclei reproduce by mitosis with typical chromosomes (2n=66). During interphase, they are filled with condensed chromatin which can be bleached with EDTA; they form no nucleoli. Ring-like lamellae, existing in the cavities of the chromatin mass, stain for RNA (after Bernhard) and are pronase-sensitive. These lamellae resemble the kinetochore material conserved during interphase in another karyorelictid ciliate,Trachelocerca geopetiti.     

Stimulation of Root Formation onImpatiens balsamina L. cuttings by coumarin and the associated biochemical changes

Coumarin-caused stimulation of rooting of cuttings ofImpatiens balsamina L. is associated with an increase in the endogenous contents of carbohydrates, total phenols and proteins. Peroxidase, IAA oxidase and polyphenol oxidase activities also increased in coumarin treated cuttings at the time of cell division preceding primordia formation (6–12 h after treatment). Coumarin effect on rooting as well as on related biochemical changes resembles the effect of auxins in some ways.     

Chromosome numbers of the European seagrasses

The chromosome numbers of the five European seagrasses have been determined in material from several sites along the coasts of the Atlantic Ocean, the North Sea and the Mediterranean:Zostera marina L., 2n = 12;Z. noltii Hornem., 2n = 12;Posidonia oceanica (L.)Delile, 2n = 20;Cymodocea nodosa (Ucria)Aschers., 2n = 14, 2n = 28;Halophila stipulacea (Forsk.)Aschers., 2n = 18. The difference in chromosome morphology betweenZ. marina andZ. noltii supports the division of the genus into two subgenera.     

Neue österreichische Fundorte vonAgropyron-, Bromus- undArabis-Arten sowie deren Chromosomenzahlen

Zusammenfassung Auf Uferböschungen des Donaukanals (Wien II) kommt außerAgropyron pectinatum (Mb.)Pb. (mit 2n=14 Chromosomen) auch eine offensichtlichA. desertorum (Fisch.) R. etSch. zuzuzählende, in Österreich sicher eingeschleppte Sippe (mit 2n=28+überzähligen Chromosomen) vor. Neu für Tirol istBromus ramosus Huds. s. str. (n=21).Arabis planisiliqua (Pers.)Rchb. fil. (2n=16) konnte in Niederösterreich wiederentdeckt werden.Arabis sagittata (Bertol.) DC. wächst auch im Burgenland, sie hat 2n=16 Chromosomen.     

End-to-end chromosome attachments in mitotic interphase and their possible significance to meiotic chromosome pairing

Cytological studies on telophase and early prophase in roottip cells of several plant species (Allium cepa, 2n=16; four Crepis species, including Crepis capillaris, 2n=6; Callitriche hermaphroditica, 2n=6; Nigella arvensis, 2n=12; Secale cereale, 2n=14) revealed that chromosome ends are attached two by two forming chains of chromosomes (interphase associations). In these chains homologous chromosomes are presumably located adjacent to each other. In Crepis capillaris it was observed that the two nucleolar chromosomes form a separate ring one end attached to the ring of the four remaining chromosomes and the other end attached to the nucleolus. It is proposed that these end-to-end attachments have significance for chromosome pairing in meiosis. The adjacent location of homologous chromosomes in the interphase associations would facilitate rapid and regular synapsis.     

Evidence for homologous pairing of chromosomes prior to meiotic prophase in maize

Relative positions of homologous heterochromatic regions of maize chromosomes were studied at premeiotic interphase, at tapetal mitotic interphase and at root tip mitotic interphase. In all three kinds of cell homologues were found to be situated significantly nearer to each other than to heterologues. It is concluded that some degree of homologous chromosome pairing may occur widely at anaphase or telophase (where it is easily overlooked) and that therefore, as has been previously suggested, homologues may be loosely aligned throughout premeiotic interphase in preparation for their subsequent synapsis.     

Intermediate symmetry in lawsone biosynthesis

Feeding experiments in Impatiens balsamina have established that 2-¹⁴C-acetate predominantly labels C-2 of lawsone. This finding confirms previous biosynthetic postulates, indicates that no symmetrical intermediate is involved in lawsone biosynthesis, and sheds light on the final steps in that process. The experimental methods that have been employed in this series of studies are also described in detail.     

Seasonal Variations in GA3 Effects on Flowering of Impatiens balsamina, a Qualitative Short Day Plant

The effectiveness of GA₃ in inducing floral-bud initiation in Impatiens balsamina under non-inductive photopcriods varies considerably at different parts of the year and appears to be determined by the prevailing temperature conditions. The period of floral-bud initiation is shortest in October and February and increases both with decreasing temperatures in November and with increasing temperatures in August and September. Floral buds do not initiate in March and April, during which time the temperature increases considerably subsequent to the start of experiment.     

Cytogenetic evidence for the specific distinction of an Alaskan marmot,Marmota broweri Hall and Gilmore (Mammalia: Sciuridae)

Summary Cytogenetic studies based upon somatic cells (bone marrow) have disclosed that the marmot hitherto designated Marmota caligata broweri Hall and Gilmore, occurring in the Brooks Range of arctic Alaska, differs from M. c. caligata (Eschscholtz) in number of chromosomes (2n=36 as compared with 2n=42 in M. caligata) and in proportions of chromosomal types. Typical karyograms for the two species are presented. It is concluded that the Brooks Range marmot is specifically distinct from M. caligata, the applicable name being Marmota broweri Hall and Gilmore. Also determined were diploid chromosome numbers for two other Nearctic species of marmots, M. flaviventris (Audubon and Bachman), with 42, and M. olympus (Merriam), with 40. It is suggested that M. broweri survived the last (Wisconsin) glaciations in the amphi-Beringian refugium, and that its closest affinities may be with one of the Eurasian species of Marmota.