Absence of microspore polarity, symmetric divisions and pollen cell fate in Brachiaria decumbens (Gramineae)

Genome ◽  
2003 ◽  
Vol 46 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Roberto Gargione Junqueira Filho ◽  
Andréa Beatriz Mendes-Bonato ◽  
Maria Suely Pagliarini ◽  
Nilton Cesar Pires Bione ◽  
Cacilda Borges do Valle ◽  
...  
Keyword(s):  
Cell Fate ◽  
Nuclear Polarization ◽  
Male Gametophyte ◽  
Chromatin Condensation ◽  
Generative Cell ◽  
Pollen Grains ◽  
Pollen Mitosis ◽  
Male Sterile ◽  
Brachiaria Decumbens ◽  
Pollen Cell

Meiotic division and male gametophyte development were analyzed in one tetraploid (2n = 4x = 36) accession of Brachiaria decumbens cv. Basilisk that showed some pollen sterility. Meiotic process was typical of polyploids in that it consisted of multiple chromosome associations. Precocious chromosome migration to the poles, laggards, and micronucleus formation were abundant in both meiosis I and II and resulted in tetrads with micronuclei. After callose dissolution, microspores were released into the anther locule and had the semblance of being normal. Although each microspore initiated its differentiation by pollen mitosis, in 43.24% of the microspores, nuclear polarization was not observed and the typical hemispherical cell plate was not detected. Division was symmetric and microspores lacked differentiation between the vegetative and the generative cell. Both nuclei were of equal size, presented equal chromatin condensation, and had a spherical shape. After the first pollen mitosis and cytokinesis, each cell underwent a new symmetric mitosis without nuclear polarization. At the end of the second pollen mitosis, four equal nuclei were observed in each pollen grain. After the second cytokinesis, the cells gave rise to four equal-sized pollen grains with a similar tetrad configuration that initially remained together. Sterile pollen grains resulted from abnormal pollen mitosis. This anomaly may be explained by a mutation, probably affecting microtubule cytoskeleton formation. The importance of this male-sterile mutation for Brachiaria breeding programs is discussed.Key words: Brachiaria decumbens, male sterility, pollen mitosis, microspore polarity, symmetric division, pollen cell fate, grasses.

scholarly journals The Arabidopsis thaliana gametophytic mutation gemini pollen1 disrupts microspore polarity, division asymmetry and pollen cell fate

Development ◽  
1998 ◽  
Vol 125 (19) ◽  
pp. 3789-3799 ◽  
Author(s):  
S.K. Park ◽  
R. Howden ◽  
D. Twell
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Fate ◽  
Asymmetric Cell Division ◽  
Marker Gene ◽  
Generative Cell ◽  
Polar Axis ◽  
Cell Polarization ◽  
Pollen Mitosis ◽  
Daughter Cells ◽  
Potential Mode

Pollen development and male gametogenesis are critically dependent upon cell polarization leading to a highly asymmetric cell division termed pollen mitosis I. A mutational approach was adopted in Arabidopsis thaliana to identify genes involved these processes. Four independent gemini pollen mutants were isolated which produce divided or twin-celled pollen. The gemini pollen1 mutant was characterized in detail and shown to act gametophytically resulting in reduced transmission through both sexes. gemini pollen1 showed an incompletely penetrant phenotype resulting in equal, unequal and partial divisions at pollen mitosis I. The division planes in gemini pollen1 were shown to be aligned with the polar axis (as in wild type) and evidence was obtained for incomplete nuclear migration, which could account for altered division symmetry. gemini pollen1 also showed division phenotypes consistent with spatial uncoupling of karyokinesis and cytokinesis suggesting that GEMINI POLLEN1 may be required for the localization of phragmoplast activity. Cell fate studies showed that in both equal and unequal divisions a vegetative cell marker gene was activated in both daughter cells. Daughter cells with a range of intermediate or hybrid vegetative/generative cell fates suggests that cell fate is quantitatively related to cell size. The potential mode of action of GEMINI POLLEN1 and its effects on cell fate are discussed in relation to proposed models of microspore polarity and cell fate determination.

scholarly journals Slowing Development Facilitates Arabidopsis mgt Mutants to Accumulate Enough Magnesium for Pollen Formation and Fertility Restoration

2021 ◽  
Vol 11 ◽  
Author(s):  
Xiao-Feng Xu ◽  
Xue-Xue Qian ◽  
Kai-Qi Wang ◽  
Ya-Hui Yu ◽  
Yu-Yi Guo ◽  
...  
Keyword(s):  
Fertility Restoration ◽  
Pollen Grains ◽  
General Mechanism ◽  
Wild Type ◽  
Pollen Mitosis ◽  
Male Sterile ◽  
Pollen Abortion ◽  
Slow Development ◽  
Magnesium Transporter ◽  
Pollen Formation

Magnesium (Mg) is an abundant and important cation in cells. Plants rely on Mg transporters to take up Mg from the soil, and then Mg is transported to anthers and other organs. Here, we showed that MGT6+/− plants display reduced fertility, while mgt6 plants are fertile. MGT6 is expressed in the anther at the early stages. Pollen mitosis and intine formation are impaired in aborted pollen grains (PGs) of MGT6+/− plants, which is similar to the defective pollen observed in mgt5 and mgt9 mutants. These results suggest that Mg deficiency leads to pollen abortion in MGT6+/− plants. Our data showed that mgt6 organs including buds develop significantly slower and mgt6 stamens accumulate a higher level of Mg, compared with wild-type (WT) and MGT6+/− plants. These results indicate that slower bud development allows mgt6 to accumulate sufficient amounts of Mg in the pollen, explaining why mgt6 is fertile. Furthermore, we found that mgt6 can restore fertility of mgt5, which has been reported to be male sterile due to defects in Mg transport from the tapetum to microspores and that an additional Mg supply can restore its fertility. Interestingly, mgt5 fertility is recovered when grown under short photoperiod conditions, which is a well-known factor regulating plant fertility. Taken together, these results demonstrate that slow development is a general mechanism to restore mgts fertility, which allows other redundant magnesium transporter (MGT) members to transport sufficient Mg for pollen formation.

scholarly journals Proteomic Analysis of Generative and Vegetative Nuclei Reveals Molecular Characteristics of Pollen Cell Differentiation in Lily

2021 ◽  
Vol 12 ◽  
Author(s):  
Chen You ◽  
YuPing Zhang ◽  
ShaoYu Yang ◽  
Xu Wang ◽  
Wen Yao ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Pollen Tube ◽  
Cell Fate ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Histone Variants ◽  
Molecular Characteristics ◽  
Nuclear Pore ◽  
Cell Nuclei ◽  
Pollen Cell

In plants, the cell fates of a vegetative cell (VC) and generative cell (GC) are determined after the asymmetric division of the haploid microspore. The VC exits the cell cycle and grows a pollen tube, while the GC undergoes further mitosis to produce two sperm cells for double fertilization. However, our understanding of the mechanisms underlying their fate differentiation remains limited. One major advantage of the nuclear proteome analysis is that it is the only method currently able to uncover the systemic differences between VC and GC due to GC being engulfed within the cytoplasm of VC, limiting the use of transcriptome. Here, we obtained pure preparations of the vegetative cell nuclei (VNs) and generative cell nuclei (GNs) from germinating lily pollens. Utilizing these high-purity VNs and GNs, we compared the differential nucleoproteins between them using state-of-the-art quantitative proteomic techniques. We identified 720 different amount proteins (DAPs) and grouped the results in 11 fate differentiation categories. Among them, we identified 29 transcription factors (TFs) and 10 cell fate determinants. Significant differences were found in the molecular activities of vegetative and reproductive nuclei. The TFs in VN mainly participate in pollen tube development. In comparison, the TFs in GN are mainly involved in cell differentiation and male gametogenesis. The identified novel TFs may play an important role in cell fate differentiation. Our data also indicate differences in nuclear pore complexes and epigenetic modifications: more nucleoporins synthesized in VN; more histone variants and chaperones; and structural maintenance of chromosome (SMC) proteins, chromatin remodelers, and DNA methylation-related proteins expressed in GN. The VC has active macromolecular metabolism and mRNA processing, while GC has active nucleic acid metabolism and translation. Moreover, the members of unfolded protein response (UPR) and programmed cell death accumulate in VN, and DNA damage repair is active in GN. Differences in the stress response of DAPs in VN vs. GN were also found. This study provides a further understanding of pollen cell differentiation mechanisms and also a sound basis for future studies of the molecular mechanisms behind cell fate differentiation.

Pollen germination of Tsuga heterophylla in vitro

1971 ◽  
Vol 49 (1) ◽  
pp. 117-119 ◽  
Author(s):  
RongHui Ho ◽  
Oscar Sziklai
Keyword(s):  
Male Gametophyte ◽  
Generative Cell ◽  
Calcium Nitrate ◽  
Pollen Grains ◽  
Potassium Nitrate ◽  
Tsuga Heterophylla ◽  
The Body ◽  
Stalk Cell

The development of the male gametophyte from western hemlock (Tsuga heterophylla (Raf.) Sarg.) pollen was complete after 5 days of incubation. This normally takes at least 6 weeks in vivo. The pollen was cultured in a solution containing boron, calcium nitrate, magnesium sulfate, and potassium nitrate. In 2 days the generative cell divided into the body cell and the stalk cell and after a further 3 days the body nucleus divided into two sperm nuclei. Morphological descriptions and measurements of the germinating pollen grains were made.

An original mutation in soybean (Glycine max (L.) Merrill) involving degeneration of the generative cell and causing male sterility

Genome ◽  
2002 ◽  
Vol 45 (6) ◽  
pp. 1257-1261 ◽  
Author(s):  
Nilton Cesar Pires Bione ◽  
Maria Suely Pagliarini ◽  
Leones Alves de Almeida
Keyword(s):  
Male Sterility ◽  
Chromosome Segregation ◽  
High Frequency ◽  
Male Gametophyte ◽  
Spontaneous Mutation ◽  
Generative Cell ◽  
Recessive Gene ◽  
Pollen Sterility ◽  
Male Sterile ◽  
Glycine Max L

A spontaneous mutation causing male sterility has been detected in line BR97-17739 from the soybean breeding program conducted by Embrapa – National Soybean Research Center. Meiotic division and male gametophyte development were analyzed in 10 male-sterile, female-fertile plants. Meiotic process had few irregularities related to chromosome segregation and affected about 2% of tetrads. Despite the high frequency of normal microspores, pollen sterility was total. After callose dissolution, microspores were released into the anther loculle and interphase nucleus was displaced from the center to one side of the cell. Displacement continued throughout normal microspore mitosis (PMI). After telophase, the hemispherical phragmoplast marked the place of cytokinesis. A typical generative cell, adjacent to the plasma membrane, and the vegetative one, containing most of the cytoplasm, were formed. In spite of the well-formed generative cell, pollen mitosis (PMII) failed to occur. The generative cell degenerated and was completely destroyed. The 3:1 segregation for male sterility in this line and its progenies indicate that a single recessive gene controls mutation.Key words: soybean, microsporogenesis, microgametogenesis, mutation, male sterility, generative cell.

The development of the male gametophyte and spermatogenesis in Taxus baccata L

1986 ◽  
Vol 228 (1250) ◽  
pp. 85-96 ◽  
Keyword(s):  
Pollen Tube ◽  
De Novo ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Equal Size ◽  
Taxus Baccata ◽  
Transverse Wall ◽  
Proximal Pole ◽  
Spermatogenous Cell ◽  
Tube Cell

The development of the male gametophyte of Taxus baccata has been studied over a period of 20 weeks, from germination of the microspore in February to spermatogenesis in July. A few days after germination the microspore nucleus divides and a transverse wall forms at the equator cutting off the small generative cell and a large tube cell. The latter immediately begins to expand to form the pollen tube. The first division thus establishes the polarity of the gametophyte and the generative cell is regarded as proximal. The transverse wall is ephemeral, and within six weeks it has disappeared. The nucleus of the generative cell divides while still at the proximal pole. The two daughter nuclei are unequal in size, but they remain associated and together move distally. The larger nucleus eventually becomes the nucleus of the spermatogenous cell, and the smaller the sterile nucleus. The spermatogenous cell acquires a distinctive cytoplasm and becomes surrounded by a wall which arises de novo . The nucleus of the spermatogenous cell enlarges, but always remains towards one side of the cell so that at mitosis the spindle is contained within one hemisphere. After division the wall of the spermatogenous cell is ruptured and the two sperms are released as naked nuclei of equal size. The cytoplasm of the spermatogenous cell degenerates as it enters the tube, but remains recognizable until fertilization.

scholarly journals Construction of a weight-based seed sorting system for the third-generation hybrid rice

Rice ◽  
2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Jianxin Wu ◽  
Shijun Qiu ◽  
Menglong Wang ◽  
Chunjue Xu ◽  
Xing Wang Deng ◽  
...  
Keyword(s):  
Hybrid Rice ◽  
Pollen Grains ◽  
Third Generation ◽  
Male Sterile ◽  
Specific Expression ◽  
The Third ◽  
Genes Encoding ◽  
Wild Type Male ◽  
Sorting System ◽  
Generation Hybrid

Abstract Background The third-generation hybrid rice technology can be constructed by transforming a recessive nuclear male sterile (NMS) mutant with a transgenic cassette containing three functional modules: the wild type male fertility gene to restore the fertility of the mutant, the pollen killer gene that specifically kills the pollen grains carrying the transgene, and the red fluorescence protein (RFP) gene to mark the transgenic seed (maintainer). The transgenic plant produces 1:1 NMS seeds and maintainer seeds that can be distinguished by the RFP signal. However, the RFP signals in the partially filled or pathogen-infected maintainer seeds are often too weak to be detected by RFP-based seed sorting machine, resulting in intermingling of the maintainer seeds with NMS seeds. Results Here we constructed a weight-based seed sorting system for the third-generation hybrid rice technology by silencing the genes encoding ADP-glucose pyrophosphorylase (AGP) essential for endosperm starch biosynthesis via endosperm-specific expression of artificial microRNAs (amiRNAs). In this system, the NMS seeds have normal endosperm and are heavy, but the maintainer seeds have shrunken endosperms and are light-weighted. The maintainer seeds can be easily and accurately sorted out from the NMS seeds by weight-sorting machines, so pure and fully filled NMS seeds are available. Conclusions The weight-based seed sorting system shows obvious advantages over the RFP-based seed sorting system in accuracy, efficiency, and cost for propagation of pure male sterile seeds. These characteristics will significantly increase the value and transgenic safety of the third-generation hybrid rice technology.

scholarly journals Prunus necrotic ringspot virus Early Invasion and Its Effects on Apricot Pollen Grain Performance

2007 ◽  
Vol 97 (8) ◽  
pp. 892-899 ◽  
Author(s):  
Khalid Amari ◽  
Lorenzo Burgos ◽  
Vicente Pallas ◽  
María Amelia Sanchez-Pina
Keyword(s):  
Developmental Stages ◽  
Generative Cell ◽  
Pollen Grains ◽  
Growth Zone ◽  
Pollen Tubes ◽  
Climatic Conditions ◽  
Pollen Grain ◽  
Ringspot Virus ◽  
Prunus Necrotic Ringspot Virus

The route of infection and the pattern of distribution of Prunus necrotic ringspot virus (PNRSV) in apricot pollen were studied. PNRSV was detected both within and on the surface of infected pollen grains. The virus invaded pollen during its early developmental stages, being detected in pollen mother cells. It was distributed uniformly within the cytoplasm of uni- and bicellular pollen grains and infected the generative cell. In mature pollen grains, characterized by their triangular shape, the virus was located mainly at the apertures, suggesting that PNRSV distribution follows the same pattern as the cellular components required for pollen tube germination and cell wall tube synthesis. PNRSV also was localized inside pollen tubes, especially in the growth zone. In vitro experiments demonstrated that infection with PNRSV decreases the germination percentage of pollen grains by more than half and delays the growth of pollen tubes by ≈24 h. However, although PNRSV infection affected apricot pollen grain performance during germination, the presence of the virus did not completely prevent fertilization, because the infected apricot pollen tubes, once germinated, were able to reach the apricot embryo sacs, which, in the climatic conditions of southeastern Spain, mature later than in other climates. Thus, infected pollen still could play an important role in the vertical transmission of PNRSV in apricot.

scholarly journals Transformation of Seed Non-Transmissible Hop Viroids in Nicotiana benthamiana Causes Distortions in Male Gametophyte Development

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2398
Author(s):  
Lenka Steinbachová ◽  
Jaroslav Matoušek ◽  
Gerhard Steger ◽  
Helena Matoušková ◽  
Sebastjan Radišek ◽  
...  
Keyword(s):  
Nicotiana Benthamiana ◽  
Male Gametophyte ◽  
Pollen Grains ◽  
Potato Spindle Tuber Viroid ◽  
Apple Fruit ◽  
Mature Pollen ◽  
Rare Occurrence ◽  
Gametophyte Development ◽  
Male Gametophyte Development ◽  
Marker Proteins

Viroids are small, non-coding, parasitic RNAs that promote developmental distortions in sensitive plants. We analyzed pollen of Nicotiana benthamiana after infection and/or ectopic transformation with cDNAs of citrus bark cracking viroid (CBCVd), apple fruit crinkle viroid (AFCVd) and potato spindle tuber viroid (PSTVd) variant AS1. These viroids were seed non-transmissible in N. benthamiana. All viroids propagated to high levels in immature anthers similar to leaves, while their levels were drastically reduced by approximately 3.6 × 103, 800 and 59 times in mature pollen of CBCVd, AFCVd and PSTVd infected N. benthamiana, respectively, in comparison to leaves. These results suggest similar elimination processes during male gametophyte development as in the Nicotiana tabacum we presented in our previous study. Mature pollen of N. benthamiana showed no apparent defects in infected plants although all three viroids induced strong pathological symptoms on leaves. While Nicotiana species have naturally bicellular mature pollen, we noted a rare occurrence of mature pollen with three nuclei in CBCVd-infected N. benthamiana. Changes in the expression of ribosomal marker proteins in AFCVd-infected pollen were detected, suggesting some changes in pollen metabolism. N. benthamiana transformed with 35S-driven viroid cDNAs showed strong symptoms including defects in pollen development. A large number of aborted pollen (34% and 62%) and a slight increase of young pollen grains (8% and 15%) were found in mature pollen of AFCVd and CBCVd transformants, respectively, in comparison to control plants (3.9% aborted pollen and 0.3% young pollen). Moreover, pollen grains with malformed nuclei or trinuclear pollen were found in CBCVd-transformed plants. Our results suggest that “forcing” overexpression of seed non-transmissible viroid led to strong pollen pathogenesis. Viroid adaptation to pollen metabolism can be assumed as an important factor for viroid transmissibility through pollen and seeds.

scholarly journals Tradescantia bracteata pollen in vitro: pollen tubes development and mitosis

2015 ◽  
Vol 46 (4) ◽  
pp. 587-598 ◽  
Author(s):  
E. Lewandowska ◽  
M. Charzyńska
Keyword(s):  
Pollen Tube ◽  
Generative Cell ◽  
Metaphase Plate ◽  
Pollen Grains ◽  
Neutral Red ◽  
Generative Nucleus ◽  
Mitotic Spindles ◽  
Germinating Pollen ◽  
Vacuolar System

About 90 per cent of <i>Tradescantia bracteata</i> pollen germinates <i>in vitro</i> after 15 min. Mitosis starts in the pollen tube after about 3 h. The mitotic trans-formations of chromosomes within the generative nucleus are not synchronized. They involve succesively the linearly arranged chromosomes in the elongated generative nucleus. In metaphase the chromosomes are arranged tandem-like linearly along the pollen tube. The chromatides translocate in anaphase from various distances to the poles in a plane parallel to the metaphase plate. This suggests that chromosomes have individual mitotic spindles and that coordination of the chromosome transformations in the generative cell is much less strict than in a typical somatic mitosis. Starch is the storage material of pollen grains. In the vegetative cytoplasm of mature pollen grains minute reddish-orange vesicular structures are visible after staining with neutral red. They do not fuse with the vacuoles proper arising in germinating pollen grains to form the vacuolar system of the pollen tube.

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