Majority Of Angiosperms Research Articles

Notes on the floral sexuality of some species of the tree genus <i>Triplaris</i> (Polygonaceae)

The majority of angiosperms (~94 %) are synoecious, with only a small minority separating the production of the two gamete types onto different biological individuals (dioecy). For many plant species, however, reproductive systems and habits are not well documented. This is particularly true of tropical trees, which, despite their conspicuity, are poorly understood. Plants in the genus Triplaris have been consistently described as strictly dioecious. After morphologic analysis using a dissecting microscope, here I present a number of fully-formed perfect (hermaphroditic) flowers observed on Triplaris herbaria specimens.

Embriogeneza u Crassulaceae: strukturalny aspekt rozwoju wieszadełka

The suspensor in the majority of angiosperms is an evolutionally conserved embryonic organ functioning as a conduit that connects ovule tissues with the embryo proper for nutrients and growth regulators flux. In this article the present knowledge on the embryo-suspensor ultrastructure and function in representatives of Crassulaceae genera: Sedum, Jovibarba, Sempervivum, Aeonium, Monanthes, Aichryson and Echeveria. The role of the suspensor in the transport of nutrients from the tissues of the ovule to the proper embryo is confirmed by the structure of the basal cell, especially the nature of the micropylar part of its wall, the "transfer wall". The basal suspensor cell is a site of intense metabolic activity. The special attention is paid to the plasmodesmata. The correlation between types of suspensors and structure of plasmodesmata was investigated. Final conclusions are given and the presented data summarized.

Auxin guides germ-cell specification in Arabidopsis anthers

Germ cells (GCs) are the key carriers delivering genetic information from one generation to the next. In a majority of animals, GCs segregate from somatic cells during embryogenesis by forming germlines. In land plants, GCs segregate from somatic cells during postembryonic development. In a majority of angiosperms, male GCs (archesporial cells) initiate at the four corners of the anther primordia. Little is known about the mechanism underlying this initiation. Here, we discovered that the dynamic auxin distribution in developing anthers coincided with GC initiation. A centripetal auxin gradient gradually formed toward the four corners where GCs will initiate. Local auxin biosynthesis was necessary for this patterning and for GC specification. The GC determinant protein SPOROCYTELESS/NOZZLE (SPL/NZZ) mediated the effect of auxin on GC specification and modified auxin biosynthesis to maintain a centripetal auxin distribution. Our work reveals that auxin is a key factor guiding GC specification in Arabidopsis anthers. Moreover, we demonstrate that the GC segregation from somatic cells is not a simple switch on/off event but rather a complicated process that involves a dynamic feedback circuit among local auxin biosynthesis, transcription of SPL/NZZ, and a progressive GC specification. This finding sheds light on the mystery of how zygote-derived somatic cells diverge into GCs in plants.

Development of Embryo Suspensors for Five Genera of Crassulaceae with Special Emphasis on Plasmodesmata Distribution and Ultrastructure.

The suspensor in the majority of angiosperms is an evolutionally conserved embryonic structure functioning as a conduit that connects ovule tissues with the embryo proper for nutrients and growth factors flux. This is the first study serving the purpose of investigating the correlation between suspensor types and plasmodesmata (PD), by the ultrastructure of this organ in respect of its full development. The special attention is paid to PD in representatives of Crassulaceae genera: Sedum, Aeonium, Monanthes, Aichryson and Echeveria. The contribution of the suspensor in transporting nutrients to the embryo was confirmed by the basal cell structure of the suspensor which produced, on the micropylar side of all genera investigated, a branched haustorium protruding into the surrounding ovular tissue and with wall ingrowths typically associated with cell transfer. The cytoplasm of the basal cell was rich in endoplasmic reticulum, mitochondria, dictyosomes, specialized plastids, microtubules, microbodies and lipid droplets. The basal cell sustained a symplasmic connection with endosperm and neighboring suspensor cells. Our results indicated the dependence of PD ultrastructure on the type of suspensor development: (i) simple PD are assigned to an uniseriate filamentous suspensor and (ii) PD with an electron-dense material are formed in a multiseriate suspensor. The occurrence of only one or both types of PD seems to be specific for the species but not for the genus. Indeed, in the two tested species of Sedum (with the distinct uniseriate/multiseriate suspensors), a diversity in the structure of PD depends on the developmental pattern of the suspensor. In all other genera (with the multiseriate type of development of the suspensor), the one type of electron-dense PD was observed.

Current Strategies of Polyploid Plant Genome Sequence Assembly.

Polyploidy or duplication of an entire genome occurs in the majority of angiosperms. The understanding of polyploid genomes is important for the improvement of those crops, which humans rely on for sustenance and basic nutrition. As climate change continues to pose a potential threat to agricultural production, there will increasingly be a demand for plant cultivars that can resist biotic and abiotic stresses and also provide needed and improved nutrition. In the past decade, Next Generation Sequencing (NGS) has fundamentally changed the genomics landscape by providing tools for the exploration of polyploid genomes. Here, we review the challenges of the assembly of polyploid plant genomes, and also present recent advances in genomic resources and functional tools in molecular genetics and breeding. As genomes of diploid and less heterozygous progenitor species are increasingly available, we discuss the lack of complexity of these currently available reference genomes as they relate to polyploid crops. Finally, we review recent approaches of haplotyping by phasing and the impact of third generation technologies on polyploid plant genome assembly.

Partitioning of vessel resistivity in three liana species.

Vessels with simple perforation plates, found in the majority of angiosperms, are considered the evolutionarily most advanced conduits, least impeding the xylem sap flow. Nevertheless, when measured, their hydraulic resistivity (R, i.e., inverse value of hydraulic conductivity) is significantly higher than resistivity predicted using Hagen-Poiseuille equation (RHP). In our study we aimed (i) to quantify two basic components of the total vessel resistivity - vessel lumen resistivity and end wall resistivity, and (ii) to analyze how the variable inner diameter of the vessel along its longitudinal axis affects resistivity. We measured flow rates through progressively shortened stems of hop (Humulus lupulus L.), grapevine (Vitis vinifera L.), and clematis (Clematis vitalba L.) and used elastomer injection for identification of open vessels and for measurement of changing vessel inner diameters along its axis. The relative contribution of end wall resistivity to total vessel resistivity was 0.46 for hop, 0.55 for grapevine, and 0.30 for clematis. Vessel lumen resistivity calculated from our measurements was substantially higher than theoretical resistivity - about 43% for hop, 58% for grapevine, and 52% for clematis. We identified variation in the vessel inner diameter as an important source of vessel resistivity. The coefficient of variation of vessel inner diameter was a good predictor for the increase of the ratio of integral RHP to RHP calculated from the mean value of inner vessel diameter. We discuss the fact that we dealt with the longest vessels in a given stem sample, which may lead to the overestimation of vessel lumen resistivity, which consequently precludes decision whether the variable vessel inner diameter explains fully the difference between vessel lumen resistivity and RHP we observed.

A Conserved Role for the NAM/miR164 Developmental Module Reveals a Common Mechanism Underlying Carpel Margin Fusion in Monocarpous and Syncarpous Eurosids.

The majority of angiosperms are syncarpous- their gynoecium is composed of two or more fused carpels. In Arabidopsis thaliana, this fusion is regulated through the balance of expression between CUP SHAPED COTYLEDON (CUC) genes, which are orthologs of the Petunia hybrida transcription factor NO APICAL MERISTEM (NAM), and their post-transcriptional regulator miR164. Accordingly, the expression of a miR164-insensitive form of A. thaliana CUC2 causes a radical breakdown of carpel fusion. Here, we investigate the role of the NAM/miR164 genetic module in carpel closure in monocarpous plants. We show that the disruption of this module in monocarpous flowers of A. thaliana aux1-22 mutants causes a failure of carpel closure, similar to the failure of carpel fusion observed in the wild-type genetic background. This observation suggested that closely related mechanisms may bring about carpel closure and carpel fusion, at least in A. thaliana. We therefore tested whether these mechanisms were conserved in a eurosid species that is monocarpous in its wild-type form. We observed that expression of MtNAM, the NAM ortholog in the monocarpous eurosid Medicago truncatula, decreases during carpel margin fusion, suggesting a role for the NAM/miR164 module in this process. We transformed M. truncatula with a miR164-resistant form of MtNAM and observed, among other phenotypes, incomplete carpel closure in the resulting transformants. These data confirm the underlying mechanistic similarity between carpel closure and carpel fusion which we observed in A. thaliana. Our observations suggest that the role of the NAM/miR164 module in the fusion of carpel margins has been conserved at least since the most recent common ancestor of the eurosid clade, and open the possibility that a similar mechanism may have been responsible for carpel closure at much earlier stages of angiosperm evolution. We combine our results with studies of early diverging angiosperms to speculate on the role of the NAM/miR164 module in the origin and further evolution of the angiosperm carpel.

Effects of abiotic factors and species interactions on estimates of male plant function: a meta‐analysis

The majority of angiosperms are hermaphroditic with total fitness comprised of both male and female components of reproduction. However, most studies examining the effects of abiotic factors and species interactions on fitness have focussed on female reproduction, potentially biasing our understanding of the consequences of environmental factors on total fitness. Here, we use meta-analysis to test how environmental factors affect male function. We obtained 278 effect sizes from 96 studies that measured male function responses to manipulated environmental factors. We found significant effects of abiotic factors and species interactions on estimates of male function, with responses varying depending on environmental factor identity. Male and female responses were correlated for abiotic factor manipulations, but varied based on the type of species interaction (antagonistic or mutualistic). This suggests that measuring only female function may misrepresent whole-plant reproduction depending on context. Finally, we found differences amongst components of male function in response to environmental factors, suggesting that some male function estimates may fail to capture the effects of environmental factors on male fitness. Our results demonstrate the importance of incorporating male function into ecological and evolutionary studies to provide a more accurate understanding of the effects of environmental factors on total fitness.

Analysis of sexual polymorphism of the plant from subclass Rosidae in Siberia

Sexual systems and association with several ecological and life history attributes were examined for 977 native angiosperms of subclass Rosidae in Siberia. The majority of angiosperms in Siberia are hermaphrodites (87.7%, N = 867). The most widespread forms of sexual differentiations are andromonoecy, gynodioecy, and dioecy. The rarest forms of sexual differentiations are monoecy, trioecy, and androdioecy. Seven of 34 families are the richest in species with sexual differentiation: Aceraceae, Elaeagnaceae, Haloragaceae, Rhamnaceae, Dipsacaceae, Apiaceae, and Geraniaceae.

Development and structure of the female gametophyte in Austrobaileya scandens (Austrobaileyaceae)

Austrobaileyales, comprising the four families Austrobaileyaceae, Trimeniaceae, Schisandraceae, and Illiciaceae, are included in the basal angiosperms along with Amborellaceae and Nymphaeaceae. Here, we present the first developmental study of the female gametophyte in Austrobaileya scandens, the only species of Austrobaileyaceae, which are sister to the rest of the Austrobaileyales. Austrobaileya scandens has a four-celled/four-nucleate embryo sac as in the derived families of the order, e.g., Illiciaceae and Schisandraceae. It is monosporic, with the chalazal megaspore of a tetrad developing into the embryo sac composed of an egg cell, two synergids, and one polar nucleus. This mode of embryo sac formation was first reported in Schisandra over 40 years ago and should now be established as the Schisandra type. Its occurrence in A. scandens shows that the Schisandra-type embryo sac is likely common to the whole Austrobaileyales as well as to Nymphaeaceae. Amborellaceae were recently reported to have an eight-celled/nine-nucleate embryo sac, clarifying that none of the basal angiosperms has the seven-celled/eight-nucleate Polygonum-type embryo sac found in the majority of angiosperms, and that the Polygonum-type embryo sac represents a derived character state in angiosperms.

Isolation of enhanced eicosapentaenoic acid producing mutants of Nannochloropsis oculata ST‐6 using ethyl methane sulfonate induced mutagenesis techniques and their characterization at mRNA transcript level

SUMMARYEthyl methane sulfonate‐induced mutagenesis techniques were used to obtain cerulenin and erythromycin resistant mutant strains, which show a marked increase of 29 and 12%, respectively, in eicosapentaenoic acid content compared to the wild type (WT) strain. The increase in eicosapentaenoic acid content in both strains correlated well with a concomitant increase in 14:0, 16:0, 16:1, 18:0 and 20:4 n − 6 content of fatty acids. However, the linoleic acid content increased only in the cerulenin resistant strain, whereas the erythromycin resistant strain was completely devoid of this fatty acid, providing a contrasting feature for further study. Partial characterization of the mutant strains based on whole cell ultrastructure, growth patterns with or without selection pressure as well as at different temperatures revealed that the mutants were more thermotolerant, and maintained their morphological and genomic fidelity, although minor changes in band patterns were noted with random amplified polymorphic DNA techniques compared to the WT strain. Therefore, the developed new strains could have wider applications as planktonic feed for the mariculture industry. Further characterization of the mutants at the molecular level revealed that steady‐state mRNA transcript levels of chloroplast‐localized Δ12 desaturase and stearoyl‐ACP desaturase genes showed a contrasting transcript profile. However, the level of endoplasmic reticulum‐localized Δ12 desaturase mRNA transcript in either of the mutant strains was almost equal to that of the WT strain. Based on this observation, we postulate that the complete loss of 18:2 fatty acid content in the erythromycin resistant strain might be a result of mutation in the chloroplast‐localized Δ12 desaturase gene and that the increased content of very long chain‐polyunsaturated fatty acids might result from extrachloroplastic lipid desaturase activity, a phenomenon similar to that in the majority of angiosperms.

Reduction in amounts of mitochondrial DNA in the sperm cells as a mechanism for maternal inheritance in Hordeum vulgare.

It is known that extranuclear organelle DNA is inherited maternally in the majority of angiosperms. The mechanisms for maternal inheritance have been well studied in plastids but not in mitochondria. In the present study we examined the mitochondrial DNA in the male reproductive cells of Hordeum vulgare L. by immunoelectron microscopy. Our results show that the number of anti-DNA gold particles on sections of sperm cell mitochondria decreased by 97% during pollen development. The reduction occurred rapidly in the generative cells and subsequently in the sperm cells, concomitant with a remarkable reduction in mitochondrial volume. It seems that the copy numbers of mitochondrial DNA were reduced in the male reproductive cells, which may be a possible mechanism by which paternal transmission is inhibited. Unlike mitochondria, plastids are excluded from the generative cells during the first pollen mitosis. These data suggest a mechanism for maternal inheritance of mitochondria in angiosperms and for independent control of inheritance of mitochondria and plastids in H. vulgare.

A rare continual flowering strategy and its influence on offspring quality in a gynodioecious plant

The majority of angiosperms have a single annual bout of reproduction; species that flower continually throughout the year are rare. Ochradenus baccatus is a gynodioecious, desert shrub whose principal flowering period is associated with the winter rains, although large individuals also remain in flower during the hot, dry summer. The goal of this study was to examine the reproductive consequences of continual flowering in a large population of O. baccatus in Israel. Over the two years of this study, 60% of individuals flowered continuously. The number of fruit and seeds per fruit were greater in winter. Winter seeds were ∼12% heavier than summer seeds and had significantly higher germination rates (80 vs. 60%, respectively). Although summer seeds were smaller and less likely to germinate, we propose that the benefit derived from their production lies in their ability to capitalize on the first winter rains. These early rain events provide a head start on establishment and growth in the hostile desert environment. Plants that delay reproduction until the onset of rains risk having their offspring face the dry conditions of spring and summer.

Reconciling Ecological Processes with Phylogenetic Patterns: The Apparent Paradox of Plant--Pollinator Systems

To what extent do studies of the ecology of mutualistic interactions inform us about the evolution of such relationships? As I will show below, the evolution of floral diversity seems to be based upon specialized relationships with pollinators, yet (with some obvious exceptions) the majority of angiosperms appear to be promiscuously pollinated by a range of taxa. This apparent discrepancy between ecological process and phylogenetic pattern is worth exploring in some detail. Consider four facts regarding plantpollinator interactions:

Stomatal Size in Fossil Plants: Evidence for Polyploidy in Majority of Angiosperms

Three published estimates of the frequency of polyploidy in angiosperms (30 to 35 percent, 47 percent, and 70 to 80 percent) were tested by estimating the genome size of extinct woody angiosperms with the use of fossil guard cell size as a proxy for cellular DNA content. The inferred chromosome numbers of these extinct species suggest that seven to nine is the primitive haploid chromosome number of angiosperms and that most angiosperms (approximately 70 percent) have polyploidy in their history.