I only have minor comments shown in below. Page 3, line 55 Are the actin cables surrounding sperm nucleus generated by actin polymerization on the envelope, or do the actin cables just adhere to sperm nucleus?
Page 4, line 24 In , Ohnishi et al. Page 5, line22 This sentence emphasizes significance of plasmogamy block after fertilization. Page 5, line 38 Those references also described relatively weak polyspermy block in the central cell.
Page 9, line 39 It is not clear why nourishing zygote by maternal tissues is required for rapid clearance of maternal factors, MTZ and ZGA.
Figure 2 The authors use too many colors to the nuclei without explanation. Five major processes are covered: 1 gamete nuclear migration, 2 karyogamy, 3 polyspermy block, 4 zygotic genome activation, and 5 asymmetric division of the zygote. For each process, cellular dynamics, structure, and other important characters are described briefly for animals and more comprehensively for plants.
Genes involved in regulating specific aspects of the process in flowering plants are highlighted. The information on how relevant characters have evolved within land plants is discussed in the context of understanding the evolution of the unique mode of sexual reproduction in flowering plants.
General comments: 1 The illustrations for figures 1 and 2 are quite good, in that they strike an appropriate balance between how much detail is included while having a clear, easily interpreted appearance. Specific Comments: Page 1, line 3: As the manuscript discusses gamete nuclear migration and karyogamy, the title should be broadened.
Page 2, lines it should be noted that pollen tubes are present in gymnosperms, and some gymnosperms have flagellate sperm while other gymnosperm lineages have immobile sperm. Page 2, lines not all central cells are homodiploid similarly, for line 46, not all endosperm is triploid.
Page 9, lines Embryo development relies on maternal tissues in at least some animals ie: mammals - perhaps specify early ie: pre-implantation for mammals embryo development. Log in. Web of Science. Identifiers publons. Navigate Abstract. Pre-publication review final round Decision letter, Jun Author response, Jun Decision letter, Jun Reviewer report, Jun Reviewer report, Apr Author response, Mar Decision letter, Feb Reviewer report, Jan Reviewer report, Dec Publication History.
Cellular dynamics of double fertilization and early embryogenesis in flowering plants Published in Journal of Experimental Zoology Part B: Molecular and Developmental Evolution on July 08, Abstract Flowering plants angiosperms perform a unique double fertilization in which two sperm cells fuse with two female gamete cells in the embryo sac to develop a seed.
Metrics Publons score from 0 scores? Score publication. Add review. DateJun Ref. R2 Dear Dr Kawashima: I am pleased to inform you that your manuscript, Cellular dynamics of double fertilization and early embryogenesis in flowering plants, is now acceptable for publication in JEZ Part B: Molecular and Developmental Evolution.
Hoboken, NJ email: jezbprod wiley. Decision letter by. Cite this decision letter. Author response by. Cite this author response. R1 Dear Dr Kawashima: Your paper is accepted, but we need to you fix some minor typos suggested by Reviewer 2 see below. For each criticism raised, please provide: The criticism from the reviewer.
The response and explanation of how the manuscript has been modified in response to the criticism. Reviewer: 2 Comments to the Author General Comments: Thank you to the authors for addressing all concerns with the previous manuscript.
Reviewed by. Cite this review. Authors answered all the comments. REVIEWER 1: 1 Page 3, line 55 Are the actin cables surrounding sperm nucleus generated by actin polymerization on the envelope, or do the actin cables just adhere to sperm nucleus?
REVIEWER 2: 1 The illustrations for figures 1 and 2 are quite good, in that they strike an appropriate balance between how much detail is included while having a clear, easily interpreted appearance.
We changed the title according to your suggestion. Page 4, line 48 About GEX1. Where can we find these trees on campus? Note the difference between the fleshy-covered seeds of Ginkgo and Podocarpus , and the dry seeds of Pinus. What function would this fleshy covering have served?
The answer to this question may also explain why ginkgo seeds really stink. Compare Ephedra to the other gymnosperms. Until recently, we thought that this curious "stem plant" was closely related to flowering plants. Ephedra undergoes double fertilization , a fundamental trait of flowering plants. Recent evidence, however, suggests that Gnetophytes are more closely related to pines than to angiosperms. Examine the Podocarpus branch. This plant is related to the yew. Depending on the season, the plant may have one or more purplish fleshy-covered seeds, smaller versions of the ginkgo seeds.
The seeds are very tempting to small children, but the seeds, as well as the leaves and other parts of the plant, are toxic. You can find this tree growing all over campus and throughout the city.
Note the difference between the broad leaves of the angiosperms on display, and compare them to the needle-shaped leaves of pines.
Needles are an adaptation to conserve water in cold, dry environments. They are also an excellent shape for species like pines that rely on wind pollination why? Examine slides of the megaspore mother cell. Observe the structure of the strobilus female pine cone and note the megasporophylls and megasporangia. You will need to look at several sporangia , and possibly more than one slide, to actually find the megaspore mother cell. Notice that the sporangia sitting on the sporophylls are directly exposed to the outside air.
Gymnosperm means "naked seed". Examine slides of the male strobilus pine cone. Note the microsporangia and the microsporophylls. You can switch to high power and observe the pollen grains in the sporangia or switch to the pollen grain slide. Notice the two large wings looks like Mickey Mouse. These wings were presumed to aid in wind pollination, but recent evidence suggests they help the pollen grain float up through the micropyle to the egg.
Examine the pine cones on display. The smaller male cones are only on the tree for a short time. Ephedra is the natural source of the drug ephedrin , which is used to treat hay fever, sinus headaches, and asthma eg. Zamia floridana is the only cycad native to the U. Ginkgos are used for bonsai, as a source of herbal medicine, and as popular urban shade trees because of their yellow autumn foliage and their resistance to air pollution. Conifer seeds are very complex structures, containing cells from three generations of the tree.
Can you figure out which tissues come from which generation of the conifer? Just as Gymnosperms forced non-seed plants into the ecological background, the evolution of Angiosperms, sometime during the Cretaceous, forced gymnosperms into restricted habitats. Wherever the earth was cold or dry, gymnosperms could prevail. But in all other habitats, flowering plants rapidly became the dominant plant life.
Flowering plants are able to survive in a greater variety of habitats than gymnosperms. Flowering plants mature more quickly than gymnosperms, and produce greater numbers of seeds. The woody tissues of angiosperms are also more complex and specialized. Their seeds are enclosed in a fruit for easy dispersal by wind, water, or animals. The leaves of angiosperms are mostly thin, extended blades, with an amazing diversity of shapes, sizes, and types. The surface of the pollen grain has a complex three-dimensional structure.
This structure is unique for each species, like a floral thumbprint. It also means that pollen grains, which are abundant in the fossil record, allow us to reconstruct ancient plant communities, and these communities in turn tells us about ancient climates. All angiosperms produce flowers , reproductive structures that are formed from four whorls of modified leaves. Most flowers have showy petals to attract pollinators, bribing insects and other animals with nectar, to get them to carry the male gametophyte through the air to another flower.
Animal pollination is common in angiosperms, in contrast to the mostly wind-pollinated gymnosperms. The ovules in angiosperms are encased in an ovary, not exposed on the sporophylls of a strobilus, as they are in gymnosperms. Angiosperm means "covered seed". The ovules develop into seeds , and the wall of the ovary forms a fruit to contain those seeds.
Fruits attract animals to disperse the seeds. Flowers consist of four whorls of modified leaves on a shortened stem: sepals , petals , stamens an anther atop a slender filament , and one or more carpels. Imagine a broad leaf with sporangia fastened along the edges of the leaf. Some ferns actually look like this. Now fold that leave over along the midrib, and you've enclosed the sporangia in a protected chamber.
You've just made a carpel. The carpels are fused together to form a pistil , which consists of a stigma upper surface , a style long, slender neck , and an ovary round inner chamber at the bottom containing one or more ovules.
The flower is analogous to the strobilus of pines and more primitive plants, except that only the inner two whorls stamens and carpels actually bear sporangia. The base of the flower is called the receptacle , and the tiny stalk that holds it is the pedicel. The life cycle of flowering plants is described in more detail below. Microspores develop in microsporangia in the anthers , at the tip of the stamen. Each anther has four microsporangia.
Microspores develops by meiosis from the microspore mother cell. These microspores develop into pollen grains.
Pollen grains are the male gametophytes in flowering plants. Inside the pollen grain, the microspore divides to form two cells, a tube cell and a cell that will act as the sperm. Cross walls break down between each pair of microsporangia, forming two large pollen sacs.
These gradually dry out and split open to release the pollen. Meanwhile, inside the ovary, at the base of the carpel, the ovules, are developing, attached to the wall of the ovary by a short stalk. The megasporangia is covered by an integument , protective tissues that are actually part of the parent sporophyte.
The megaspore mother cell divides by meiosis to produce four haploid megaspores. Three of these megaspores degenerate, and the surviving fourth megaspore divides by mitosis. Each of the daughter nuclei divides again, making four nuclei, and these divide a third time, making a grand total of eight haploid nuclei. This large cell with eight nuclei is the embryo sac. This embryo sac is the female gametophyte in flowering plants.
One nucleus from each group of four migrates to the center. These are called the polar nuclei. The remaining three nuclei of each group migrates to opposite ends of the cell. Cell walls form around each group of three nuclei. The mature female gametophyte thus consists of only seven cells, three at the top, three at the bottom, and a large cell in the middle with two nuclei.
One cell of the bottom three cells will act as the egg. When the pollen grain reaches the stigma of the carpel, it germinates to form a pollen tube. This pollen tube will grow through the neck or style, all the way down to the bottom of the carpel, to a small opening called the micropyle.
The male gametophyte has two cells. One is the tube cell, the other will act as a sperm. As the pollen tube grows closer to the embryo sac, the sperm nucleus divides in two, so the mature male gametophyte has three haploid nuclei. While the pollen tube is entering the ovule, the two polar nuclei in the female gametophyte fuse together, making one diploid nucleus. The two sperm nuclei enter the embryo sac. One sperm nucleus fuses with the egg nucleus to form a diploid zygote.
The other sperm nucleus fuses with the fused polar nuclei to make a triploid cell. This 3N cell will divide repeatedly to form the endosperm, the stored nutritive material inside the seed. The integuments develop into the tough outer seed coat, which will protect the developing embryo from mechanical harm or dessication. Thus the ovule, the integuments and the megasporangium they enclose, develops into the seed.
The walls of the ovary then develop into the fruit. There is an incredible diversity of flower structure, not only in the number of sepals, petals, stamens, and carpels, but also in the way these modified leaves are attached with respect to the ovary. Linnaeus used these very characteristics to sort out the different related groups of flowering plants in his invention of binomial nomenclature, genus and species. All of these differences can affect the final physical appearance of the fruit.
In the male cones staminate cones , the microsporocytes give rise to pollen grains by meiosis. In the spring, large amounts of yellow pollen are released and carried by the wind. Some gametophytes will land on a female cone. Pollination is defined as the initiation of pollen tube growth. The pollen tube develops slowly as the generative cell in the pollen grain divides into two haploid sperm cells by mitosis.
At fertilization, one of the sperm cells will finally unite its haploid nucleus with the haploid nucleus of an egg cell. Female cones ovulate cones contain two ovules per scale. One megaspore mother cell megasporocyte undergoes meiosis in each ovule.
Three of the four cells break down leaving only a single surviving cell which will develop into a female multicellular gametophyte. It encloses archegonia an archegonium is a reproductive organ that contains a single large egg. Upon fertilization, the diploid egg will give rise to the embryo, which is enclosed in a seed coat of tissue from the parent plant. Fertilization and seed development is a long process in pine trees: it may take up to two years after pollination.
The seed that is formed contains three generations of tissues: the seed coat that originates from the sporophyte tissue, the gametophyte that will provide nutrients, and the embryo itself. In the life cycle of a conifer, the sporophyte 2n phase is the longest phase. The gametophytes 1n , microspores and megaspores, are reduced in size. This phase may take more than one year between pollination and fertilization while the pollen tube grows towards the megasporocyte 2n , which undergoes meiosis into megaspores.
The megaspores will mature into eggs 1n. Life cycle of a conifer : This image shows the life cycle of a conifer. Pollen from male cones moves up into upper branches where it fertilizes female cones. Gymnosperms are a diverse group of plants the protect their seeds with cones and do not produce flowers or fruits. Modern gymnosperms are classified into four phyla. The first three the Coniferophyta, Cycadophyta, and Gingkophyta are similar in their production of secondary cambium cells that generate the vascular system of the trunk or stem and are partially specialized for water transportation and their pattern of seed development.
However, these three phyla are not closely related phylogenetically to each other. The fourth phylum the Gnetophyta are considered the closest group to angiosperms because they produce true xylem tissue. Conifers are the dominant phylum of gymnosperms, with the most variety of species. They are typically tall trees that usually bear scale-like or needle-like leaves. Water evaporation from leaves is reduced by their thin shape and the thick cuticle.
Snow slides easily off needle-shaped leaves, keeping the load light and decreasing breaking of branches. Adaptations to cold and dry weather explain the predominance of conifers at high altitudes and in cold climates. Conifers include familiar evergreen trees such as pines, spruces, firs, cedars, sequoias, and yews.
A few species are deciduous, losing their leaves in fall. The European larch and the tamarack are examples of deciduous conifers. Many coniferous trees are harvested for paper pulp and timber.
Diversity of conifers : Conifers are the dominant form of vegetation in cold or arid environments and at high altitudes. Shown here are the a evergreen spruce Picea sp.
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