Embryoid Formation in Pollen Grains of<i>Nicotiana tabacum</i>

Sunderland, N.; Wicks, F. M.

doi:10.1093/jxb/22.1.213

Cited by 148 publications

(47 citation statements)

References 8 publications

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“…The observed methylation change is particularly interesting when it is compared with the observation that the regeneration of haploid plants is possible from pollen grains in anther cultures taken either at the single-cell stage or immediately after mitosis (11), but it becomes increasingly difficult as the pollen matures (12). Androgenic reproduction from binuclear pollen is believed to occur only from the vegetative nucleus, as the generative nucleus degenerates during tobacco anther culture (13). It may be that early methylation changes in the generative nucleus render it unable to regenerate, whereas the less severe changes to the vegetative nucleus permit its regeneration over a longer time scale.…”

Section: Discussionmentioning

confidence: 98%

Developmental changes in DNA methylation of the two tobacco pollen nuclei during maturation

Oakeley

Podestà

Jost

1997

Proc. Natl. Acad. Sci. U.S.A.

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Changes in DNA methylation during tobacco pollen development have been studied by confocal f luorescence microscopy using a monoclonal anti-5-methylcytosine (anti-m 5 C) antibody and a polyclonal anti-histone H1 (antihistone) antibody as an internal standard. The specificity of the anti-m 5 C antibody was demonstrated by a titration series against both single-stranded DNA and double-stranded DNA substrates in either the methylated or unmethylated forms. The antibody was found to show similar kinetics against both double-and single-stranded DNA, and the f luorescence was proportional to the amount of DNA used. No signal was observed with unmethylated substrates. The extent of methylation of the two pollen nuclei remained approximately constant after the mitotic division that gave rise to the vegetative and generative nuclei. However, during the subsequent development of the pollen, the staining of the generative nucleus decreased until it reached a normalized value of 1 ⁄5 of that of the vegetative nucleus. The use of a confocal microscope makes these data independent of possible focusing artefacts. The anti-histone antibody was used as a control to show that, while the antibody staining directed against 5-methylcytosine changed dramatically during pollen maturation, the histone signal did not. We observed the existence of structural dimorphism amongst tobacco pollen grains, the majority having three pollen apertures and the rest with four. However, the methylation changes observed occurred to the same extent in both subclasses.Tobacco pollen undergoes a series of well defined stages during its development. Four amphihaploid sporocytes are produced by means of a meiotic division from an amphidiploid pollen mother cell. The cells then each form a highly resilient cell wall composed primarily of callose and cellulose. The nucleus then migrates to one of the poles of the pollen grain, where it undergoes a mitotic division to give two amphihaploid daughter cells. This division is not an equal one, and the cell closest to the pollen pole contains minimal cytoplasm and is known as the generative cell because it is destined to divide and form the gametes (1). The larger cell is called the vegetative cell, and its nucleus is responsible for controlling the development of the pollen tube. The generative cell rapidly detaches from the pole and floats freely within the cytoplasm of the vegetative cell (2). The two cells are separated only by plasma membranes (2). When mature pollen germinates, it produces a pollen tube that grows chemotropically toward the ovaries (3-5). The vegetative nucleus of tobacco always enters the pollen tube first and is then followed by the generative nucleus. Shortly after this, the vegetative nucleus disintegrates. The generative cell then undergoes a second mitotic division in the pollen tube to give two amphihaploid sperm cells that can fertilize the egg and the polar nuclei in the ovary (6), resulting in the embryo and endosperm, respectively.Previous studies, using genomic sequencing...

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Section: Discussionmentioning

confidence: 98%

Developmental changes in DNA methylation of the two tobacco pollen nuclei during maturation

Oakeley

Podestà

Jost

1997

Proc. Natl. Acad. Sci. U.S.A.

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“…The most common route to sporophytic growth in B. napus and other species is through ectopic division of the microspore or vegetative cell of binucleate pollen (Sunderland and Wicks, 1971;Fan et al, 1988;Indrianto et al, 2001;Pulido et al, 2005). Sporophytic structures composed of generative-like and vegetativelike nuclei can be observed occasionally (Fan et al, 1988;Reynolds, 1993;González-Melendi et al, 1996;Kaltchuk-Santos et al, 1997;González and Jouve, 2005), but it is not known whether sustained division of generative-like cells contributes to the formation of viable embryos.…”

Section: Acquisition Of Embryo Identitymentioning

confidence: 99%

The Histone Deacetylase Inhibitor Trichostatin A Promotes Totipotency in the Male Gametophyte

et al. 2014

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The haploid male gametophyte, the pollen grain, is a terminally differentiated structure whose function ends at fertilization. Plant breeding and propagation widely use haploid embryo production from in vitro-cultured male gametophytes, but this technique remains poorly understood at the mechanistic level. Here, we show that histone deacetylases (HDACs) regulate the switch to haploid embryogenesis. Blocking HDAC activity with trichostatin A (TSA) in cultured male gametophytes of Brassica napus leads to a large increase in the proportion of cells that switch from pollen to embryogenic growth. Embryogenic growth is enhanced by, but not dependent on, the high-temperature stress that is normally used to induce haploid embryogenesis in B. napus. The male gametophyte of Arabidopsis thaliana, which is recalcitrant to haploid embryo development in culture, also forms embryogenic cell clusters after TSA treatment. Genetic analysis suggests that the HDAC protein HDA17 plays a role in this process. TSA treatment of male gametophytes is associated with the hyperacetylation of histones H3 and H4. We propose that the totipotency of the male gametophyte is kept in check by an HDAC-dependent mechanism and that the stress treatments used to induce haploid embryo development in culture impinge on this HDAC-dependent pathway.

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“…For instance, selection for characteristics to improve the plant's ability to assimilate CO2 such as increased leaf surface or altered canopy structure (15,26), delayed senescence (17), higher Chl content (1 1), or longer periods of storage of assimilates in the grain (10) The variations in ribulose-1,5-bisP carboxylase/oxygenase content and carboxylase activity have been related to net photosynthesis (3,22). Some genotypes showing differences in carboxylase activity have been found in soybean and other species, and attempts have been made to select plants with higher carboxylase activity as a way to obtain a higher photosynthetic yield (22)(23)(24) (20,25). They were surface sterilized for 10 min in a filtered solution of calcium hypochlorite (7% w/v), and rinsed in sterile water.…”

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confidence: 99%

Selection of Nicotiana tabacum Haploids of High Photosynthetic Efficiency

Medrano

Primo‐Millo²

1985

Plant Physiol.

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Photosynthetic efficiency is an important factor for crop productivity. It has been suggested that crop production could be increased by improving the photosynthetic efficiency (19,28).Although in some cases there is not a clear correlation between net photosynthesis and crop yield (9, 12), some reports show a clear positive correlation between net CO2 assimilation and dry weight accumulation (7,21,29).A great variability in photosynthetic ability is found in different species as well as within different cultivars of the same species.Differences in the CO2 assimilation rate have been observed in soybean (8), maize (14), tobacco (28), alfalfa, and cotton. This variability indicates the possibility of selecting plants with higher photosynthetic efficiency.The rate of CO2 assimilation can be increased either by improving the conditions under which photosynthesis is performed (CO2 and 02 concentrations, temperature, illumination, and nutrition, etc.), or by breeding and selection of lines with higher photosynthetic efficiency (1, 13).Photosynthetic ability of a plant can be increased in many different ways, which are directly or indirectly related to the photosynthetic processes. For instance, selection for characteristics to improve the plant's ability to assimilate CO2 such as increased leaf surface or altered canopy structure (15, 26), delayed senescence (17), higher Chl content (1 1), or longer periods of storage of assimilates in the grain (10) has been done with varied success.

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Embryoid Formation in Pollen Grains ofNicotiana tabacum

Cited by 148 publications

References 8 publications

Developmental changes in DNA methylation of the two tobacco pollen nuclei during maturation

Developmental changes in DNA methylation of the two tobacco pollen nuclei during maturation

The Histone Deacetylase Inhibitor Trichostatin A Promotes Totipotency in the Male Gametophyte

Selection of Nicotiana tabacum Haploids of High Photosynthetic Efficiency

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