Same same but different: sperm-activating EC1 and ECA1 gametogenesis-related family proteins

2014 ◽  
Vol 42 (2) ◽  
pp. 401-407 ◽  
Author(s):  
Stefanie Sprunck ◽  
Thomas Hackenberg ◽  
Maria Englhart ◽  
Frank Vogler
Keyword(s):  
Disulfide Bonds ◽  
Female Gametophyte ◽  
Flowering Plant ◽  
Egg Cell ◽  
Sequence Motifs ◽  
Double Fertilization ◽  
Functional Diversification ◽  
Synergid Cell ◽  
Related Family ◽  
Short Amino Acid Sequence

During double fertilization in Arabidopsis thaliana, the egg cell secretes small cysteine-rich EC1 (egg cell 1) proteins, which enable the arriving sperm pair to rapidly interact with the two female gametes. EC1 proteins are members of the large and unexplored group of ECA1 (early culture abundant 1) gametogenesis-related family proteins, characterized by a prolamin-like domain with six conserved cysteine residues that may form three pairs of disulfide bonds. The distinguishing marks of egg-cell-expressed EC1 proteins are, however, two short amino acid sequence motifs present in all EC1-like proteins. EC1 genes appear to encode the major CRPs (cysteine-rich proteins) expressed by the plant egg cell, and they are restricted to flowering plants, including the most basal extant flowering plant Amborella trichopoda. Many other ECA1 gametogenesis-related family genes are preferentially expressed in the synergid cell. Functional diversification among the ECA1 gametogenesis-related family is suggested by the different patterns of expression in the female gametophyte and the low primary sequence conservation.

scholarly journals Transcriptional repression specifies the central cell for double fertilization

2020 ◽  
Vol 117 (11) ◽  
pp. 6231-6236 ◽  
Author(s):  
Meng-Xia Zhang ◽  
Shan-Shan Zhu ◽  
Yong-Chao Xu ◽  
Ya-Long Guo ◽  
Wei-Cai Yang ◽  
...  
Keyword(s):  
Cell Fate ◽  
Transcriptional Repression ◽  
Female Gametophyte ◽  
Embryo Sac ◽  
Central Cell ◽  
Egg Cell ◽  
Accessory Cell ◽  
Double Fertilization ◽  
Genetic Rescue ◽  
Key Innovation

Double fertilization is a key innovation for the evolutionary success of angiosperms by which the two fertilized female gametes, the egg cell and central cell, generate the embryo and endosperm, respectively. The female gametophyte (embryo sac) enclosed in the sporophyte is derived from a one-celled haploid cell lineage. It undergoes successive events of mitotic divisions, cellularization, and cell specification to give rise to the mature embryo sac, which contains the two female gametes accompanied by two types of accessory cells, namely synergids and antipodals. How the cell fate of the central cell is specified has long been equivocal and is further complicated by the structural diversity of female gametophyte across plant taxa. Here, MADS-box protein AGL80 was verified as a transcriptional repressor that directly suppresses the expression of accessory cell-specific genes to specify the central cell. Further genetic rescue and phylogenetic assay of the AGL80 orthologs revealed a possible conserved mechanism in the Brassicaceae family. Results from this study provide insight into the molecular determination of the second female gamete cell in Brassicaceae.

scholarly journals Recent advances in understanding female gametophyte development

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 804 ◽  
Author(s):  
Debra J Skinner ◽  
Venkatesan Sundaresan
Keyword(s):  
Cell Fate ◽  
Female Gametophyte ◽  
Cell Communication ◽  
Embryo Sac ◽  
Cell Types ◽  
Egg Cell ◽  
Male Gametes ◽  
Reproductive Unit ◽  
Genetic Mechanisms ◽  
Female Gametophyte Development

The haploid female gametophyte (embryo sac) is an essential reproductive unit of flowering plants, usually comprising four specialized cell types, including the female gametes (egg cell and central cell). The differentiation of these cells relies on spatial signals which pattern the gametophyte along a proximal-distal axis, but the molecular and genetic mechanisms by which cell identities are determined in the embryo sac have long been a mystery. Recent identification of key genes for cell fate specification and their relationship to hormonal signaling pathways that act on positional cues has provided new insights into these processes. A model for differentiation can be devised with egg cell fate as a default state of the female gametophyte and with other cell types specified by the action of spatially regulated factors. Cell-to-cell communication within the gametophyte is also important for maintaining cell identity as well as facilitating fertilization of the female gametes by the male gametes (sperm cells).

scholarly journals Variability of female gametophyte of tobacco in vivo and in vitro under the influence of extreme temperatures and its possible consequences

2020 ◽  
Author(s):  
L. P. Lobanova ◽  
A. Yu. Kolesova
Keyword(s):  
Low Temperatures ◽  
Female Gametophyte ◽  
Egg Cell ◽  
Extreme Temperatures ◽  
Abnormal Embryo ◽  
High And Low Temperatures

High and low temperatures induce the formation of abnormal embryo sacks (ES). ES with additional cells in the egg cell apparatus and synergids that are similar to an egg sells are capable of producing seeds with additional and haploid embrios.

scholarly journals The SEEL Motif and Members of the MYB-related REVEILLE Transcription Factor Family are Important for the Expression of LORELEI in the Synergid Cells of the Arabidopsis Female Gametophyte

2021 ◽  
Author(s):  
Jennifer A. Noble ◽  
Alex Seddon ◽  
Sahra Uygun ◽  
Steven E. Smith ◽  
Shin-Han Shiu ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Pollen Tube ◽  
Female Gametophyte ◽  
Regulatory Networks ◽  
Clock Genes ◽  
Regulatory Element ◽  
Regulatory Elements ◽  
Loss Of Function ◽  
Seed Formation ◽  
Synergid Cell

Synergid cells in the micropylar end of the female gametophyte are required for critical cell-cell signaling interactions between the pollen tube and the ovule that precede double fertilization and seed formation in flowering plants. LORELEI (LRE) encodes a GPI-anchored protein that is expressed primarily in the synergid cells, and together with FERONIA, a receptor-like kinase, it controls pollen tube reception by the receptive synergid cell. Still, how LRE expression is controlled in synergid cells remains poorly characterized. We identified candidate cis-regulatory elements enriched in LRE and other synergid cell-expressed genes. One of the candidate motifs (TAATATCT) in the LRE promoter was an uncharacterized variant of the Evening Element motif that we named as the Short Evening Element-like (SEEL) motif. Deletion or point mutations in the SEEL motif of the LRE promoter resulted in decreased reporter expression in synergid cells, demonstrating that the SEEL motif is important for expression of LRE in synergid cells. Additionally, we found that LRE expression is decreased in the loss of function mutants of REVEILLE (RVE) transcription factors, which are clock genes known to bind the SEEL and other closely related motifs. We propose that RVE transcription factors regulate LRE expression in synergid cells by binding to the SEEL motif in the LRE promoter. Identification of a cis-regulatory element and transcription factors involved in the expression of LRE will serve as a foundation to characterize the gene regulatory networks in synergid cells and investigate the potential connection between circadian rhythm and fertilization.

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.

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