scholarly journals Highly expressed maize pollen genes display coordinated expression with neighboring transposable elements and contribute to pollen fitness

2019 ◽  
Author(s):  
Cedar Warman ◽  
Kaushik Panda ◽  
Zuzana Vejlupkova ◽  
Sam Hokin ◽  
Erica Unger-Wallace ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Transposable Elements ◽  
Vegetative Cell ◽  
Sperm Cell ◽  
Transcript Level ◽  
Flowering Plants ◽  
Sperm Cells ◽  
Double Fertilization ◽  
Maize Pollen ◽  
Coordinated Expression

AbstractIn flowering plants, the haploid male gametophyte (pollen) is essential for sperm delivery, double fertilization, and subsequent initiation of seed development. Pollen also undergoes dynamic epigenetic regulation of expression from transposable elements (TEs), but how this process interacts with gene regulation and function is not clearly understood. To identify components of these processes, we quantified transcript levels in four male reproductive stages of maize (tassel primordia, microspores, mature pollen, and isolated sperm cells) via RNA-seq. We found that, in contrast to Arabidopsis TE expression in pollen, TE transcripts in maize accumulate as early as the microspore stage and are also present in sperm cells. Intriguingly, coordinated expression was observed between the most highly expressed protein-coding genes and neighboring TEs, specifically in both mature pollen and sperm cells. To test the hypothesis that such elevated expression correlates with functional relevance, we measured the fitness cost (male-specific transmission defect) of GFP-tagged exon insertion mutations in over 50 genes highly expressed in pollen vegetative cell, sperm cell, or seedling (as a sporophytic control). Insertions in genes highly expressed only in seedling or primarily in sperm cells (with one exception) exhibited no difference from the expected 1:1 transmission ratio. In contrast, insertions in over 20% of vegetative cell genes were associated with significant reductions in fitness, showing a positive correlation of transcript level with non-Mendelian segregation. The gamete expressed2 (gex2) gene was the single sperm cell gene associated with reduced transmission when mutant (<35% for two independent insertions), and also triggered seed defects when crossed as a male, supporting a role for gex2 in double fertilization. Overall, our study demonstrates a developmentally programmed and coordinated transcriptional activation of TEs and genes, and further identifies maize pollen as a model in which transcriptomic data have predictive value for quantitative phenotypes.Author SummaryIn flowering plants, pollen is essential for delivering sperm cells to the egg and central cell for double fertilization, initiating the process of seed development. In plants with abundant pollen like maize, this process can be highly competitive. In an added layer of complexity, growing evidence indicates expression of transposable elements (TEs) is more dynamic in pollen than in other plant tissues. How these elements impact pollen function and gene regulation is not well understood. We used transcriptional profiling to generate a framework for both detailed analysis of TE expression and quantitative assessment of gene function during maize pollen development. TEs are expressed early and persist, many showing coordinate activation with highly-expressed neighboring genes in the pollen vegetative cell and sperm cells. Measuring fitness costs for a set of over 50 mutations indicates a correlation between elevated transcript level and gene function in the vegetative cell. Finally, we establish a role in fertilization for the gamete expressed2 (gex2) gene, identified based on its specific expression in sperm cells. These results highlight maize pollen as a powerful model for investigating the developmental interplay of TEs and genes, as well as for measuring fitness contributions of specific genes.

scholarly journals Polyspermy Block in the Central Cell During Double Fertilization of Arabidopsis thaliana

2021 ◽  
Vol 11 ◽  
Author(s):  
Shiori Nagahara ◽  
Hidenori Takeuchi ◽  
Tetsuya Higashiyama
Keyword(s):  
Arabidopsis Thaliana ◽  
Sperm Cell ◽  
Central Cell ◽  
Egg Cell ◽  
Sperm Cells ◽  
Potential Contribution ◽  
Double Fertilization ◽  
Male Gametes ◽  
One To One ◽  
The One

During double fertilization in angiosperms, two male gametes (sperm cells), are released from a pollen tube into the receptive region between two female gametes; the egg cell and the central cell of the ovule. The sperm cells fertilize the egg cell and the central cell in a one-to-one manner to yield a zygote and an endosperm, respectively. The one-to-one distribution of the sperm cells to the two female gametes is strictly regulated, possibly via communication among the four gametes. Polyspermy block is the mechanism by which fertilized female gametes prevent fertilization by a secondary sperm cell, and has been suggested to operate in the egg cell rather than the central cell. However, whether the central cell also has the ability to avoid polyspermy during double fertilization remains unclear. Here, we assessed the one-to-one fertilization mechanism of the central cell by laser irradiation of the female gametes and live cell imaging of the fertilization process in Arabidopsis thaliana. We successfully disrupted an egg cell within the ovules by irradiation using a femtosecond pulse laser. In the egg-disrupted ovules, the central cell predominantly showed single fertilization by one sperm cell, suggesting that neither the egg cell nor its fusion with one sperm cell is necessary for one-to-one fertilization (i.e., monospermy) of the central cell. In addition, using tetraspore mutants possessing multiple sperm cell pairs in one pollen, we demonstrated that normal double fertilization was observed even when excess sperm cells were released into the receptive region between the female gametes. In ovules accepting four sperm cells, the egg cell never fused with more than one sperm cell, whereas half of the central cells fused with more than one sperm cell (i.e., polyspermy) even 1 h later. Our results suggest that the central cell can block polyspermy during double fertilization, although the central cell is more permissive to polyspermy than the egg cell. The potential contribution of polyspermy block by the central cell is discussed in terms of how it is involved in the one-to-one distribution of the sperm cells to two distinct female gametes.

Female gametophyte-controlled pollen tube guidance

2010 ◽  
Vol 38 (2) ◽  
pp. 627-630 ◽  
Author(s):  
Mihaela-Luiza Márton ◽  
Thomas Dresselhaus
Keyword(s):  
Pollen Tube ◽  
Female Gametophyte ◽  
Cell Communication ◽  
Flowering Plants ◽  
Sperm Cells ◽  
Double Fertilization ◽  
Pollen Tube Guidance ◽  
Communication Events ◽  
Extensive Cell

During the evolution of flowering plants, their sperm cells have lost mobility and are transported from the stigma to the female gametophyte via the pollen tube to achieve double fertilization. Pollen tube growth and guidance is largely governed by the maternal sporophytic tissues of the stigma, style and ovule. However, the last phase of the pollen tube path is under female gametophyte control and is expected to require extensive cell–cell communication events between both gametophytes. Until recently, little was known about the molecules produced by the female gametophyte that are involved in this process. In the present paper, we review the most recent development in this field and focus on the role of secreted candidate signalling ligands.

scholarly journals Persistent directional growth capability in Arabidopsis thaliana pollen tubes after nuclear elimination from the apex

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kazuki Motomura ◽  
Hidenori Takeuchi ◽  
Michitaka Notaguchi ◽  
Haruna Tsuchi ◽  
Atsushi Takeda ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Sperm Cell ◽  
Pollen Tubes ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Apical Region ◽  
Basal Region ◽  
Specific Expression ◽  
Directional Growth

AbstractDuring the double fertilization process, pollen tubes deliver two sperm cells to an ovule containing the female gametes. In the pollen tube, the vegetative nucleus and sperm cells move together to the apical region where the vegetative nucleus is thought to play a crucial role in controlling the direction and growth of the pollen tube. Here, we report the generation of pollen tubes in Arabidopsis thaliana whose vegetative nucleus and sperm cells are isolated and sealed by callose plugs in the basal region due to apical transport defects induced by mutations in the WPP domain-interacting tail-anchored proteins (WITs) and sperm cell-specific expression of a dominant mutant of the CALLOSE SYNTHASE 3 protein. Through pollen-tube guidance assays, we show that the physiologically anuclear mutant pollen tubes maintain the ability to grow and enter ovules. Our findings provide insight into the sperm cell delivery mechanism and illustrate the independence of the tip-localized vegetative nucleus from directional growth control of the pollen tube.

scholarly journals Role of Transposable Elements in Gene Regulation in the Human Genome

Life ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 118
Author(s):  
Arsala Ali ◽  
Kyudong Han ◽  
Ping Liang
Keyword(s):  
Gene Regulation ◽  
Transposable Elements ◽  
Regulatory Sequences ◽  
Rna Sequences ◽  
Expression Of Genes ◽  
Wide Range ◽  
Lineage Specificity ◽  
Regulatory Rnas ◽  
Potential Factors ◽  
Interspersed Repeats

Transposable elements (TEs), also known as mobile elements (MEs), are interspersed repeats that constitute a major fraction of the genomes of higher organisms. As one of their important functional impacts on gene function and genome evolution, TEs participate in regulating the expression of genes nearby and even far away at transcriptional and post-transcriptional levels. There are two known principal ways by which TEs regulate the expression of genes. First, TEs provide cis-regulatory sequences in the genome with their intrinsic regulatory properties for their own expression, making them potential factors for regulating the expression of the host genes. TE-derived cis-regulatory sites are found in promoter and enhancer elements, providing binding sites for a wide range of trans-acting factors. Second, TEs encode for regulatory RNAs with their sequences showed to be present in a substantial fraction of miRNAs and long non-coding RNAs (lncRNAs), indicating the TE origin of these RNAs. Furthermore, TEs sequences were found to be critical for regulatory functions of these RNAs, including binding to the target mRNA. TEs thus provide crucial regulatory roles by being part of cis-regulatory and regulatory RNA sequences. Moreover, both TE-derived cis-regulatory sequences and TE-derived regulatory RNAs have been implicated in providing evolutionary novelty to gene regulation. These TE-derived regulatory mechanisms also tend to function in a tissue-specific fashion. In this review, we aim to comprehensively cover the studies regarding these two aspects of TE-mediated gene regulation, mainly focusing on the mechanisms, contribution of different types of TEs, differential roles among tissue types, and lineage-specificity, based on data mostly in humans.

scholarly journals Influence of Campylobacter fetus subsp. fetus on ram sperm cell quality

2008 ◽  
Vol 57 (11) ◽  
pp. 1405-1410 ◽  
Author(s):  
Tidhar Zan Bar ◽  
Ronen Yehuda ◽  
Tomer Hacham ◽  
Sigal Krupnik ◽  
Benjamin Bartoov
Keyword(s):  
Sperm Cell ◽  
Sperm Cells ◽  
Male Factor ◽  
Motility Index ◽  
Fas Receptor ◽  
Campylobacter Fetus ◽  
Fetus Subsp ◽  
Ram Sperm ◽  
Female Sheep

Campylobacter fetus subsp. fetus infection can occur in female sheep, causing infertility or abortion. Despite extensive research on the effect of these bacteria on female fertility, little research has been done on the influence of C. fetus subsp. fetus on the male factor. Our objective was to examine the influence of C. fetus subsp. fetus on ram sperm. Motility index, percentage of live spermatozoa, mean αt value (an indication of the chromatin stability of the sperm cell) and percentage of sperm cells expressing the FAS receptor were measured in sperm incubated in the presence or absence of C. fetus subsp. fetus. The motility index and viability of sperm incubated with the bacteria were lower than those of untreated sperm samples after 5 h. In bacteria-incubated sperm cells, the percentage expressing FAS receptor was already significantly elevated at 15 min. Bacteria-incubated sperm showed a greater prevalence of morphological damage. The bacteria were attached to tail and acrosome regions, and the sperm damage was concentrated in both the motility and chromatin regions. Bacteria-infected sperm cells showed a decrease in motility, increase in early acrosome reaction and chromatin damage. Similar effects were induced by incubation of the sperm with supernatants from C. fetus subsp. fetus cultures. Thus this study demonstrates that C. fetus subsp. fetus has a detrimental effect on the quality of ram sperm.

scholarly journals Histone H1 prevents non-CG methylation-mediated small RNA biogenesis in Arabidopsis heterochromatin

2021 ◽  
Author(s):  
Jaemyung Choi ◽  
David Bruce Lyons ◽  
Daniel Zilberman
Keyword(s):  
Dna Methylation ◽  
Transposable Elements ◽  
Small Rna ◽  
Histone H3 ◽  
Histone H1 ◽  
Dna Methyltransferases ◽  
Flowering Plants ◽  
Genomic Sequences ◽  
Rna Molecules ◽  
Rna Biogenesis

Flowering plants utilize small RNA molecules to guide DNA methyltransferases to genomic sequences. This RNA-directed DNA methylation (RdDM) pathway preferentially targets euchromatic transposable elements. However, RdDM is thought to be recruited by methylation of histone H3 at lysine 9 (H3K9me), a hallmark of heterochromatin. How RdDM is targeted to euchromatin despite an affinity for H3K9me is unclear. Here we show that loss of histone H1 enhances heterochromatic RdDM, preferentially at nucleosome linker DNA. Surprisingly, this does not require SHH1, the RdDM component that binds H3K9me. Furthermore, H3K9me is dispensable for RdDM, as is CG DNA methylation. Instead, we find that non-CG methylation is specifically required for small RNA biogenesis, and without H1 small RNA production quantitatively expands to non-CG methylated loci. Our results demonstrate that H1 enforces the separation of euchromatic and heterochromatic DNA methylation pathways by excluding the small RNA-generating branch of RdDM from non-CG methylated heterochromatin.

scholarly journals A Study of Aflatoxin on Sperm Cell Quality for Elderly People

2018 ◽  
Vol 6 (2) ◽  
pp. 45-49
Author(s):  
Akila CR ◽  
Dinesh Babu J ◽  
Sravan Kumar P ◽  
Vinaya B
Keyword(s):  
Elderly People ◽  
Sperm Cell ◽  
Sperm Cells

Mycotoxins represent poisonous materials produced via certain types of growths. Among different mycotoxins, aflatoxins are viewed as plainly hazardous, taking into account that they are portrayed as cancer-causing for creatures and individuals. The admission of aflatoxins by means of feeds or nourishments should cause pernicious results on creatures' or people's wellbeing. Exploration on creatures has indicated that the overall casing circumstance just as a portion of the blood boundaries, particularly those of the liver may be adversely influenced with aflatoxin the executives. As to conceptive device, in spite of the fact that not remarkably examined, a few specialists bolster the helpless impacts of aflatoxins both on women or on grown-up guys. More precisely, in male, the scale and weight of the genital organs, the spermatogenesis, the number, the motility and the morphology of sperm cells just as hormones' fixations can be influenced after presentation of the creatures to aflatoxins, making barrenness inconveniences additional normal. Most examination allude to lab and significantly less to viable creatures, while least complex two investigations look for counsel from the doable issues of barrenness on men in view of aflatoxins. Since imitation is made one out of the greatest fundamental areas of creature cultivation, exceptional intrigue should be paid to supplements with the goal that the chance of the aflatoxin admission by creatures could be evacuated, the creature wellbeing extraordinarily in regards to the conceptive gadget may be covered and financial misfortunes could be enhanced.

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