Types Of Tetrads Research Articles

Morphological and Ultrastructural Features of Selected Epidendroideae Pollen Dispersal Units and New Insights into Their Chemical Nature.

Orchidaceae display enormous diversity in their flower morphology, which is particularly evident in their pollen dispersal units (pollinia, pollinaria). The packaging of pollen by elastoviscin leads to a great diversity of these morphologically and structurally complex pollen units. Despite being one of the most diverse angiosperm families, the available palynological data on orchids remain limited and sometimes contradicting. This study provides new insights into the pollen morphology and ultrastructure of five orchid species from the subfamily Epidendroideae, using combined light, scanning electron, and transmission electron microscopy. The aim was to compare the morphology and ultrastructure of pollen dispersal units and to elucidate the chemical nature of the pollen wall layers and of elastoviscin. Our combined light and electron microscopy investigation demonstrated the presence of six tetrad types even within a single pollinium, which is unique for orchids. The application of different staining methods confirmed the assumed lipidic nature of elastoviscin and the differences in its contrast and ultrastructure suggest a mixture of sticky materials with dissimilar chemical compositions. This study affirmed that sporopollenin is mostly restricted to the outer pollen grains of peripheral tetrads in compact and sectile pollinia, while inner tetrads exhibit highly reduced non-sporopollenin pollen walls.

Ontogeny of Different Tetrad Types in the Single Microsporangium of Mitrephora tomentosa (Annonaceae)

Annonaceae, comprising approximately 107 genera and 2400 species, is the largest family among early-divergent Magnoliales. Previous studies have concentrated on the binding mechanism that holds together the four members of tetrads in Annonaceae. However, the development mechanisms of different tetrad types remain largely unknown. Mitrephora tomentosa was found to exhibit five permanent tetrad types, with two or three of them existing in the same microsporangium, which is ideal for studying the formation mechanisms of different permanent tetrad pollens in a single microsporangium and explaining the relationship between cytokinesis and pollen tetrad types. The ontogenetic development of the different tetrads in M. tomentosa was investigated using electron microscopy technologies, histochemical staining, and immunocytochemistry. During meiosis, pollen mother cells produce decussate and tetragonal tetrads by successive cytokinesis and produce tetrahedral and rhomboidal tetrads by simultaneous cytokinesis. Bidirectional callose deposition was observed in tetrahedral, tetragonal, rhomboidal, and decussate tetrads. The variations in the process of microsporogenesis randomly accumulate and manifest as different combinations of cytokinesis and callose deposition, leading to the formation of differently shaped tetrads. In mature permanent tetrad pollens, four microspores are connected by both simple cohesion and cytoplasmic channels, which also play an important role in maintaining the synchronization of the tetrad members.

Development of anther and sectile pollinium in Herminium lanceum (Thunb. ex Sw.) Vuijk-a massulate orchid

Abstract The role of anther characteristics in orchid taxonomy, cladistic analysis, and understanding the development and evolution of various traits is significant. Therefore, Herminium lanceum (Thunb. ex Sw.) Vuijk was selected for the study due to the lack of information about these characteristics. In this taxon, anther primordium developed two thecae directed towards the lateral side, which produced wedge-shaped, rectangular or triangular massulae through repeated mitotic divisions of archesporial cells. The anther wall developed from the outer secondary parietal layer and inner secondary parietal layer, made up of epidermis, endothecium, a middle layer, and tapetum. Each theca had a central septum that divided it into two microsporangia. Tapetum of dual origin was observed. Cytokinesis produced isobilateral, tetrahedral, linear, T-shaped and decussate types of microspore tetrads. Each microspore had a smaller lenticular generative cell and a larger spherical vegetative cell, which were formed by the mitotic division of the nucleus. Additionally, the endothecium developed ring-shaped fibrous thickenings. Massulae of two locules were united to the reticulum and formed bipartite sectile pollinium.

High-Throughput Fluorescent Pollen Tetrad Analysis Using DeepTetrad.

Meiotic recombination initiates from ~100-200s of programmed DNA double stranded breaks (DSBs) in plants. Meiotic DSBs can be repaired using homologous chromosomes to generate a crossover . Meiotic crossover is critical for chromosomal segregation and increasing genetic variation. The number of crossovers is limited to one and three per chromosome pair in most plant species. Genetic, epigenetic, and environmental factors control crossover frequency and distribution. Due to the limited number of crossovers it is challenging to measure crossover frequency along chromosomes. We adapted fluorescence-tagged lines (FTLs ) that contain quartet1 mutations and linked transgenes expressing dsRed, eYFP, and eCFP in pollen tetrads into the deep learning-based image analysis tool, DeepTetrad. DeepTetrad enables the measurement of crossover frequency and interference by classifying 12 types of tetrads from three-color FTLs in a high-throughput manner, using conventional microscope instruments and a Linux machine. Here, we provide detailed procedures for preparing tetrad samples, tetrad imaging, running DeepTetrad, and analysis of DeepTetrad outputs. DeepTetrad-based measurements of crossover frequency and interference ratio will accelerate the genetic dissection of meiotic crossover control.

How to deduce the seven basic class asci of ordered tetrads in Neurospora

Genetic analysis is an important part of undergraduate genetics teaching and tetrad analysis is unique and integral for genetic analysis of fungi. The ordered tetrad in Neurospora is an important material for genetic analysis, which can not only be used to study recombination between genes and centromeres, but also between genes themselves, as well as study the fine cross patterns between non-sister chromatids of homologous chromosomes. However, in textbooks and related professional journals, there is a lack of specific introduction to the induction methods of the seven basic class asci used in two genes analysis. In the present paper, we designed a table presenting the correlation between the three tetrad types (PD, NPD, T) and the four segregation pattern groups (Ⅰ Ⅰ, Ⅱ Ⅱ, Ⅰ Ⅱ, Ⅱ Ⅰ) to visually show the 12 possible combinations (3×4=12). Then five of them were excluded through the "×" symbol and in addition with three comments attached with the table, thus finally we obtained seven basic ascus types. We hope that this analytical method can assist the teaching of ordered tetrad analysis in Neurospora.

Topology-based classification of tetrads and quadruplex structures

MotivationQuadruplexes attract the attention of researchers from many fields of bio-science. Due to a specific structure, these tertiary motifs are involved in various biological processes. They are also promising therapeutic targets in many strategies of drug development, including anticancer and neurological disease treatment. The uniqueness and diversity of their forms cause that quadruplexes show great potential in novel biological applications. The existing approaches for quadruplex analysis are based on sequence or 3D structure features and address canonical motifs only.ResultsIn our study, we analyzed tetrads and quadruplexes contained in nucleic acid molecules deposited in Protein Data Bank. Focusing on their secondary structure topology, we adjusted its graphical diagram and proposed new dot-bracket and arc representations. We defined the novel classification of these motifs. It can handle both canonical and non-canonical cases. Based on this new taxonomy, we implemented a method that automatically recognizes the types of tetrads and quadruplexes occurring as unimolecular structures. Finally, we conducted a statistical analysis of these motifs found in experimentally determined nucleic acid structures in relation to the new classification.Availability and implementation https://github.com/tzok/eltetrado/ Supplementary information Supplementary data are available at Bioinformatics online.

Further Interpretation of Wodehouseia spinata Stanley from the Late Maastrichtian of the Far East (China)

Dispersed pollen grains Wodehouseia spinata Stanley of unknown botanical affinity from the Maastrichtian of the Amur River Region, Far East are studied using transmitted light, scanning and transmission electron microscopy. The pollen was probably produced by wetland or aquatic plants, adapted to a sudden change in the water regime during the vegetation season. The pattern of the exine sculpture and sporoderm ultrastructure suggests that insects contributed to pollination. The flange and unevenly thickened endexine could facilitate harmomegathy. A tetragonal or rhomboidal tetrad type seems to be most logical for Wodehouseia pollen. The infratectum structure suggests that Wodehouseia should be placed within an advanced group of eudicots.

Formation pattern in five types of pollen tetrad in Pseuduvaria trimera (Annonaceae).

In basal angiosperms, there are several types of permanent tetrad but their formation pattern remains elusive. Pseuduvaria trimera has five types of tetrads and is the species with the most abundant tetrad types in Annonaceae. In order to interpret the formation pattern of different tetrad types, pollen development was investigated from the microspore mother cell stage to the bicellular pollen stage and the ultrastructure of pollen wall in the five tetrad types using light microscopy, transmission electron microscopy, and confocal laser scanning microscopy. Both successive and intermediate cytokinesis were observed within the same anther. The nucleus location of the microspores together with cytokinesis determine the number and the spatial arrangement of callose plates, and further have an effect on the tetrad types. The anthers with or without septation and the arrangement of microsporocytes might be also related to the tetrad type. The individual pollen grains within the tetrads are connected with each other by crosswall cohesion and cytoplasmic channels at localized points in the proximal walls. The various types of tetrads, cytokinesis, and cohesion in P. trimera reflect the high diversity in pollen development, which enhances the dramatic variety in pollen morphology in this family. Our observations of the development of tetrads provided some new insights for interpreting the factors influencing the types of tetrads, and reported the existence of a cytoplasmic channel in Annonaceae for the first time.

Early Cretaceous palm pollen tetrads from Patagonia, Argentina

Pollen tetrads and monads of spiny pollen grains with close affinities to palms have been found in several localities from the Lower Cretaceous (Barremian-Albian) of the Austral Basin (Magallanes), Patagonia (Argentina). When found dispersed, spiny and zonasulcate pollen grains, are commonly referred to the fossil genus Spinizonocolpites Muller, with close affinities to the extant palm Nypa. The Patagonian specimens were compared with fossil and extant members of the Arecaceae, showing close similarities in shape and sculpture with the primitive members of the subfamily Calamoideae. Nypa produces tetragonal tetrads different from the tetrahedral tetrads of the Spinizonocolpites-type recovered from Patagonia. The specimens were studied with LM and SEM. The polarity, aperture orientation and tetrad type allow segregating the Patagonian grains from the Nypoideae and relating it to the Calamoideae subfamily. These records suggest an antique origin of monocots and a probably initial diversification of calamoid palms during the Early Cretaceous in high latitudes of Gondwana. The presence of palmae during the Early Cretaceous in southern South America suggests a warm and humid climate, similar to that found in present days at tropics.

Ultrastructure and development of sporoderm in Aristolochia clematitis (Aristolochiaceae)

The purpose of this study was to investigate the sporoderm development of inaperturate pollen grains in Aristolochia clematitis (Aristolochiaceae). During successive microsporogenesis several types of tetrads are formed; no tetrahedral tetrads were observed. In the tetrad period, the primexine is observed around the perimeter of microspores. In the free microspore period, a thick lamellar endexine develops around the perimeter of the microspore; the thick tubular intine appears later in this period. At the maturation of pollen grains, the intine is stratified into two layers: an outer tubular ectintine and an inner homogeneous endintine. Finally, the intine forms an aperture thickening. The thickened intine deforms and displaces the endexine and tears the ectexine apart. This shows that pollen grains of A. clematitis are aperturate. The apertures are colpi.

하이부쉬 블루베리의 품종별 화기 특성 및 형태적 관찰

Morphology and characteristics of floral organ in highbush blueberry cultivars were studied to select suitable cultivars of highbush blueberry for domestic cultivation. The stamen consists an anther and a tape-like hairy filament with well-developed trichomes. When the anther was opened, the wall of anther was not dehiscent, and pollen grains were discharged into two tubes. Pollen was mature tetrad type without being separated after meiosis (Late March). The number of pollen granules per anther was 400~1,300, the germination rate was higher in the cultivars having many pollen grains. Pistil was composed of five carpels and a shipper without separate part. The number of ovules per ovary was 39~67, therefore, the coefficient of ranged from 11.6 to 31.0%. The seed pod formation by combination of 'Bluejay' and 'Sharpblue' was higher in the cross-pollination than in the self-pollination.

Investigation of mitosis, microsporogenesis and pollen germination in the critically endangered plantAmsonia orientalis(Apocynaceae)

Amsonia orientalis Decne. (Apocynaceae) is a medically useful and critically endangered plant which has very restricted distribution world-wide. The root tips and flower buds of A. orientalis were used as an experimental material and they were squashed in aceto-orcein. Fresh flowers and a liquid medium were used for pollen germination tests. In spite of the small size of the cells and chromosomes, all phases of mitosis and meiosis were observed. Generally the phases of mitosis were regular but there were a few abnormalities, such as laggard chromosome in metaphase and bridge formation in anaphase. There was a good relationship between the stages of pollen development and floral bud length. As a result of the cytokinesis, tetrahedral types of tetrads were occurred in microsporogenesis. The tetrad nuclei resulting from the simultaneous type of meiosis were found to be of equal size. Pollen germination had started from the first hour and pollen tube lengths and germination percentages regularly increased wit...

Microspore wall organisation and ultrastructure in two species of Selaginella (Lycophyta) producing permanent tetrads

Spore morphology and ultrastructural features of the permanent microspore tetrads of Selaginella convoluta and S. lepidophylla were studied with light microscopy, scanning and transmission electron microscopy. The four members of each tetrad in S. convoluta are linked together through a common envelope and form an unbroken complex system of alveoli that connects the equatorial and distal regions of the microspores. In the proximal exospore of microspores, no differentiation referable to an apertural fold was observed but an interruption of the exospore is evident in that area in germinating microspores. The distal exospore is composed of three strata: inner zone, intermediate zone and outer alveolar. In S. lepidophylla tetrads, the four microspores are assembled within a common tetrad envelope and are equatorially connected by a prominent ridge. The distal regions of the microspores are free. In the proximal exospore of microspores, no differentiation referable to an apertural fold was observed. The tetrad envelope appears as a wide common coat, which, on the surface and depending on the regions, is granular or alveolate, centrally perforated and, in section, consists of a single layer or forms a two-layered, more or less intricate, network. This envelope has the same contrast as the exospore outer layer and shows, in its median zone, cavities with opaque contents, quite similar to those of the microspore exospore layer. These two different types of tetrads emphasise the outstanding structural diversity of the microspore sporoderm in living Selaginellaceae.

Pollen tetrad segregation and pollen ovule ratios in six species of Acrotriche (Styphelioideae: Ericaceae)

Pollen morphology can be useful in the determination of phylogeny and mating systems of plants. Pollen ovule ratios can give an indication of the mating system of plant species, and there are a number of theories as to reductions in response to pollination strategies. Pollen tetrad segregation occurs when a number of pollen grains within a tetrad abort; this process has evolved a number of times in the family Ericaceae. Pollen ovule ratios along with the total number of tetrads, number of viable grains and proportions of each of the tetrad types were investigated in six species of Acrotriche (Styphelioideae: Ericaceae). Pollen ovule ratios were used in comparison with related species to give indications of mating systems and to examine theories regarding reductions in pollen production. The study species can be arranged into distinct groupings based on the proportions of tetrad types that correlate with floral morphology and may be indicative of phylogentic associations.

On the Reproductive Biology of Tribulus Terrestris L. (Zygophyllaceae): Embryological Features; Pollen and Seed Viability

ABSTRACTAn embryological study of Tribulus terrestris from the Bulgarian flora was carried out. The anther is tetrasporangiate and its wall, the development of which follows the Dicotyledonous type, consists of epidermis, fibrous endothecium, two middle layers and glandular tapetum. Different types of microspore tetrads are formed after simultaneous microsporogenesis. The mature pollen grains are two-celled. The mature ovule is anatropous, bitegmic, crassinucellate with one-celled archesporium. The development of the embryo sac follows the Polygonum (monosporic) type. The formation of endothelium and hypostase were reported. The legitimate embryo and endosperm develop after double fertilization. Initially, the endosperm is nuclear. The embryogenesis runs according to the Solanad type. A high pollen and embryo viability was estimated.

Development of Triticum aestivum-Leymus racemosus ditelosomic substitution line 7Lr#1S(7A) with resistance to wheat scab and its meiotic behavior analysis

Leymus racemosus is highly resistant to wheat scab (Fusarum head bright). The transfer of scab resistant gene from L. racemosus to Triticum aestivum is of great significance for broadening the base of wheat resistance. In the present study, the pollen of T. aestivum-L. racemosus monosomic addition line with scab resistance was treated by irradiation with 1200 R 60Co-γ-rays prior to pollinating to emasculated wheat cv. Mianyang 85–45. Nine plants with a telocentric chromosome 7Lr#1S were observed in M1, and one ditelosomic substitution line 7Lr#1S was selected from selfcrossing progenies and confirmed by chromosome C-banding and GISH. Furthermore, a co-dominant EST-SSR marker CINAU 31 was employed to identify this substitution line. A pair of chromosome 7A of common wheat were found to be replaced by a pair of telocentric chromosome 7Lr#1S, and further investigation showed that chromosome configuration of the substitution line at MI of PMCs after GISH was 17.50 W + 2.19 W + 0.42 7Lr#1S + 1.08 I7Lr#1S + 0.69 IW. Two telocentric chromosomes paired as a bivalent in 59.7% of PMCs. Abnormal chromosome behaviors of telocentric chromosomes were observed in part of PMCs at anaphase I and telophase I, including the moving of two telocentric chromosomes to the same pole, lagging and earlier separation of their sister chromatid. All these abnormal behaviors can be grouped into three distinct types of tetrads according to different numbers of 7Lr#1S in their daughter cells and various micronucleus in some tetrads. However, due to the high transmission frequency of the female and male gametes with a 7Lr#1S, 84% of the selfcrossing progeny plants had ditelosomic substitution. The substitution line showed high resistance to wheat scab in a successive two-year test both in the greenhouse and field; hence, the line will be particularly valuable for alien gene mapping, small fragment translocation induction and telosomic cytological behavior analysis.

Polymorphism in β-cyclodextrin–benzoic acid inclusion complex: a kinetically controlled crystal growth according to the Ostwald’s rule

Crystal form II of the β-cyclodextrin–benzoic acid (β-CD–BA) inclusion complex was obtained from the 1.5-year stored aqueous EtOH solution of β-CD and BA as 2β-CD·1.5BA·0.7EtOH·21H 2O in the monoclinic space group C2 with unit cell constants: a = 19.413(3), b = 24.306(4), c = 32.975(1) Å, β = 104.41(1)°. By contrast, the desired crystal form I in the triclinic space group P1 that ever grew up from the fresh solution as 2β-CD·2BA·0.7EtOH·20.65H 2O was not reproducible any more [Aree, T.; Chaichit, N. Carbohydr. Res. 2003, 338, 439–446]. In the two crystal forms, β-CDs are isostructural with a ‘round’ conformation stabilized by intramolecular O-3( n)⋯O-2( n + 1) hydrogen bonds. The BA inclusion geometries are similar with a preferred orientation, that is, BAs are situated above the O-4 plane, point their COOH groups to the β-CD O-6 side, incline 52° with respect to the O-4 plane and are mainly maintained in positions by hydrogen bonding with the surrounding water molecules. β-CDs form dimers as structural motif of different packing modes: the screw-channel type in form II and the average of intermediate and tetrad types in form I. Polymorphism in the β-CD–BA inclusion complex is a kinetically controlled crystal growth following the Ostwald’s rule: the less stable crystal form I grew up first within one week from the fresh solution, whereas the more stable crystal form II appeared after 1.5-year storage.

Why does some pollen lack apertures? A review of inaperturate pollen in eudicots

Apertures are key characters of pollen grains with systematic importance in angiosperms. They function as sites for pollen tube exit, water uptake, transfer of recognition substances and accommodation of volume changes. Not all pollen has apertures; inaperturate pollen (lacking obvious apertures) characterizes many angiosperm groups, especially in early divergent angiosperms and monocots, but also eudicots. In order to expand our knowledge of the systematic distribution, possible functional significance and development of inaperturate pollen in angiosperms, this review focuses on inaperturate and cryptoaperturate (with hidden apertures) pollen in the large eudicot clade, which comprises about 75% of present-day angiosperm species. It includes new TEM observations of inaperturate pollen from four exemplar taxa selected from different parts of the eudicot phylogeny. Two categories of inaperturate (including cryptoaperturate) pollen occur in eudicots. (1) Sterile attractant or feeding pollen associated with functional dioecy has evolved iteratively at least six times in conjunction with complex breeding systems in the core eudicots. (2) Fertile pollen has evolved numerous times independently throughout eudicots, though generally in a relatively small number of individual taxa. Notable exceptions are the petaliferous crotonoid Euphorbiaceae s.s., in which fertile inaperturate pollen occurs in c. 1500 species, and two subfamilies of Apocynaceae s.l. (Secamonoideae and Asclepiadoideae) with c. 2500 species with fertile inaperturate pollen in pollinia. Fertile inaperturate pollen is sometimes (but not always) associated with an aquatic habit, parasitism, insectivory, heterostyly, anemophily or pollinia. Most fertile inaperturate pollen has a thin exine, or the exine is largely restricted to isolated components (muri, protuberances, subunits) separated by thinner areas which probably function as apertures. In cryptoaperturate pollen, the aperture is covered by continuous exine which probably has a protective function, similar to an operculum. Developmentally, inaperturate pollen is not associated with any particular tetrad type or meiotic spindle orientation (unlike some apertures) due to the absence of a colpal shield of endoplasmic reticulum or other organelles and hence is independent of microsporogenesis type. The lack of a colpal shield during the tetrad stage of development permits complete deposition of first primexine and then exine around each microspore, possibly mediated by the action of the DEX1 protein. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 29‐48.

Chemical insight from crystallographic disorder-structural studies of supramolecular photochemical systems. Part 2. The β-cyclodextrin–4,7-dimethylcoumarin inclusion complex: a new β-cyclodextrin dimer packing type, unanticipated photoproduct formation, and an examination of guest influence on β-CD dimer packing

As part of an ongoing structural study of supramolecular photochemical β-cyclodextrin(β-CD)–coumarin derivatives systems the crystal structure of the β-CD–4,7-dimethylcoumarin complex has been determined at 13 K and complemented with ab initio molecular orbital calculations on selected guest coumarin molecules. The 4,7-dimethylcoumarin molecules form a crystalline 2∶2 host–guest (H–G) complex with β-CD that is appropriately described as a “reaction nano-vessel” in which the inter-molecular interactions of import to the outcome of the reaction are confined to a single β-CD dimer host. Structure determination of the isolated photoproduct showed the product formed is the anti-HT photodimer. Production of this dimer is only possible with much rearrangement of the guests. This appears to occur because of a preferential spatial fit of this product to the β-CD dimer cavity. The crystal structure reveals a new β-CD dimer packing pattern, designated tetrad type, with reduced reaction tube intermolecular interactions among guest molecules. Tetrad packing is characterized in comparison with the previously reported β-CD dimer packing types. Guest influence on packing of β-CD dimers is examined in β-CD inclusion complexes with different derivatized coumarins. To probe basic molecular properties giving rise to inter-molecular interactions influencing crystal packing, ab initio molecular orbital calculations for the guest coumarin molecules were carried out to examine electrostatic interactions.

Intra‐specific pollen polymorphism in Mimosa pigra (Mimosaceae)

Five different types of pollen tetrads were detected from the short and long stamens of the male and hermaphrodite flowers of the androdioecious species, Mimosa pigra L. Light (LM) and scanning electron microscopes (SEM) were used in this study to redescribe the pollen forms and to identify the various pollen types encountered. An identification key and relative percentages of these pollen types were also presented. The study showed that the long stamens of the male flowers and those of the hermaphrodite ones have five (I, II, III, IV and V) and two (I and V) pollen types respectively, whereas the short stamens of both male and hermaphrodite flowers have only one pollen type (type I). We report here the first incidence of intra‐specific pollen polymorphism in androdioecious species.