The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Thomas Dresselhaus - One of the best experts on this subject based on the ideXlab platform.

  • friend or foe signaling mechanisms during Double Fertilization in flowering seed plants
    Current Topics in Developmental Biology, 2019
    Co-Authors: Liangzi Zhou, Thomas Dresselhaus
    Abstract:

    Since the first description of Double Fertilization 120 years ago, the processes of pollen tube growth and guidance, sperm cell release inside the receptive synergid cell, as well as fusion of two sperm cells to the female gametes (egg and central cell) have been well documented in many flowering plants. Especially microscopic techniques, including live cell imaging, were used to visualize these processes. Molecular as well as genetic methods were applied to identify key players involved. However, compared to the first 11 decades since its discovery, the past decade has seen a tremendous advancement in our understanding of the molecular mechanisms regulating angiosperm Fertilization. Whole signaling networks were elucidated including secreted ligands, corresponding receptors, intracellular interaction partners, and further downstream signaling events involved in the cross-talk between pollen tubes and their cargo with female reproductive cells. Biochemical and structural biological approaches are now increasingly contributing to our understanding of the different signaling processes required to distinguish between compatible and incompatible interaction partners. Here, we review the current knowledge about signaling mechanisms during above processes with a focus on the model plants Arabidopsis thaliana and Zea mays (maize). The analogy that many of the identified "reproductive signaling mechanisms" also act partly or fully in defense responses and/or cell death is also discussed.

  • Maternal ENODLs Are Required for Pollen Tube Reception in Arabidopsis
    Current Biology, 2016
    Co-Authors: Philipp Cyprys, Qingpei Huang, Andrea Bleckmann, Hongya Gu, Ying Zhang, Thomas Dresselhaus
    Abstract:

    Summary During the angiosperm (flowering-plant) life cycle, Double Fertilization represents the hallmark between diploid and haploid generations [1]. The success of Double Fertilization largely depends on compatible communication between the male gametophyte (pollen tube) and the maternal tissues of the flower, culminating in precise pollen tube guidance to the female gametophyte (embryo sac) and its rupture to release sperm cells. Several important factors involved in the pollen tube reception have been identified recently [2–6], but the underlying signaling pathways are far from being understood. Here, we report that a group of female-specific small proteins, early nodulin-like proteins (ENODLs, or ENs), are required for pollen tube reception. ENs are featured with a plastocyanin-like (PCNL) domain, an arabinogalactan (AG) glycomodule, and a predicted glycosylphosphatidylinositol (GPI) anchor motif. We show that ENs are asymmetrically distributed at the plasma membrane of the synergid cells and accumulate at the filiform apparatus, where arriving pollen tubes communicate with the embryo sac. EN14 strongly and specifically interacts with the extracellular domain of the receptor-like kinase FERONIA, localized at the synergid cell surface and known to critically control pollen tube reception [6]. Wild-type pollen tubes failed to arrest growth and to rupture after entering the ovules of quintuple loss-of-function EN mutants, indicating a central role of ENs in male-female communication and pollen tube reception. Moreover, overexpression of EN15 by the endogenous promoter caused disturbed pollen tube guidance and reduced fertility. These data suggest that female-derived GPI-anchored ENODLs play an essential role in male-female communication and Fertilization.

  • plant reproduction amor enables males to respond to female signals
    Current Biology, 2016
    Co-Authors: Thomas Dresselhaus, Silvia Coimbra
    Abstract:

    The pollen tube of flowering plants undertakes a long journey to transport two sperm cells for Double Fertilization. New work on pollen tube guidance has identified an arabinogalactan-derived ovular factor that primes tubes to respond to female gametophyte-secreted attraction signals.

  • peptide signalling during the pollen tube journey and Double Fertilization
    Journal of Experimental Botany, 2015
    Co-Authors: Li-jia Qu, Ling Li, Thomas Dresselhaus
    Abstract:

    : Flowering seed plants (angiosperms) have evolved unique ways to protect their gametes from pathogen attack and from drying out. The female gametes (egg and central cell) are deeply embedded in the maternal tissues of the ovule inside the ovary, while the male gametes (sperm cells) are enclosed in the vegetative pollen tube cell. After germination of the pollen tube at the surface of papilla cells of the stigma the two immobile sperm cells are transported deep inside the sporophytic maternal tissues to be released inside the ovule for Double Fertilization. Angiosperms have evolved a number of hurdles along the pollen tube journey to prevent inbreeding and Fertilization by alien sperm cells, and to maximize reproductive success. These pre-zygotic hybridization barriers require intensive communication between the male and female reproductive cells and the necessity to distinguish self from non-self interaction partners. General molecules such as nitric oxide (NO) or gamma-aminobutyric acid (GABA) therefore appear to play only a minor role in these species-specific communication events. The past 20 years have shown that highly polymorphic peptides play a leading role in all communication steps along the pollen tube pathway and Fertilization. Here we review our current understanding of the role of peptides during reproduction with a focus on peptide signalling during self-incompatibility, pollen tube growth and guidance as well as sperm reception and gamete activation.

  • three cell fusions during Double Fertilization
    Cell, 2015
    Co-Authors: Stefanie Sprunck, Thomas Dresselhaus
    Abstract:

    Fertilization of both egg and central cell is a major distinguishing feature of flowering plants. Now, Maruyama et al. report a third cell fusion event between the persistent synergid and the fertilized central cell shortly after Double Fertilization in Arabidopsis. This causes rapid dilution of pollen tube attractant(s), preventing polytubey.

Tetsuya Higashiyama - One of the best experts on this subject based on the ideXlab platform.

  • polyspermy block in the central cell during Double Fertilization of arabidopsis thaliana
    Frontiers in Plant Science, 2021
    Co-Authors: Shiori Nagahara, Tetsuya Higashiyama, Hidenori Takeuchi
    Abstract:

    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.

  • the male gamete membrane protein dmp9 dau2 is required for Double Fertilization in flowering plants
    Development, 2018
    Co-Authors: Taro Takahashi, Shiori Nagahara, Tetsuya Higashiyama, Toshiyuki Mori, Kenji Ueda, Lixy Yamada, Hitoshi Sawada, Tomoko Igawa
    Abstract:

    ABSTRACT All flowering plants exhibit a unique type of sexual reproduction called ‘Double Fertilization’ in which each pollen tube-delivered sperm cell fuses with an egg and a central cell. Proteins that localize to the plasma membrane of gametes regulate one-to-one gamete pairing and fusion between male and female gametes for successful Double Fertilization. Here, we have identified a membrane protein from Lilium longiflorum generative cells using proteomic analysis and have found that the protein is an ortholog of Arabidopsis DUF679 DOMAIN MEMBRANE PROTEIN 9 (DMP9)/DUO1-ACTIVATED UNKNOWN 2 (DAU2). The flowering plant DMP9 proteins analyzed in this study were predicted to have four transmembrane domains and be specifically expressed in both generative and sperm cells. Knockdown of DMP9 resulted in aborted seeds due to single Fertilization of the central cell. Detailed imaging of DMP9-knockdown sperm cells during in vivo and semi-in vitro Double Fertilization revealed that DMP9 is involved in gamete interaction that leads to correct Double Fertilization.

  • live imaging of calcium spikes during Double Fertilization in arabidopsis
    Nature Communications, 2014
    Co-Authors: Yuki Hamamura, Moe Nishimaki, Hidenori Takeuchi, Anja Geitmann, Daisuke Kurihara, Tetsuya Higashiyama
    Abstract:

    Ca(2+) waves and oscillation are key signalling elements during the Fertilization process of animals, and are involved, for example, in egg activation. In the unique Double Fertilization process in flowering plants, both the egg cell and the neighbouring central cell fuse with a sperm cell each. Here we succeeded in imaging cytosolic Ca(2+) in these two cells, and in the two synergid cells that accompany the gametes during semi-in vivo Double Fertilization. Following pollen tube discharge and plasmogamy, the egg and central cells displayed transient Ca(2+) spikes, but not oscillations. Only the events in the egg cell correlated with the plasmogamy. In contrast, the synergid cells displayed Ca(2+) oscillations on pollen tube arrival. The two synergid cells showed distinct Ca(2+) dynamics depending on their respective roles in tube reception. These Ca(2+) dynamics in the female gametophyte seem to represent highly specific signatures that coordinate successful Double Fertilization in the flowering plants.

  • independent control by each female gamete prevents the attraction of multiple pollen tubes
    Developmental Cell, 2013
    Co-Authors: Daisuke Maruyama, Daichi Susaki, Ryushiro D Kasahara, Yuki Hamamura, Moe Nishimaki, Hidenori Takeuchi, Daisuke Kurihara, Tetsuya Higashiyama
    Abstract:

    In flowering plants, Double Fertilization is normally accomplished by the first pollen tube, with the fertilized ovule subsequently inhibiting the attraction of a second pollen tube. However, the mechanism of second-pollen-tube avoidance remains unknown. We discovered that failure to fertilize either the egg cell or the central cell compromised second-pollen-tube avoidance in Arabidopsis thaliana. A similar disturbance was caused by disrupting the Fertilization-independent seed (FIS) class polycomb-repressive complex 2 (FIS-PRC2), a central cell- and endosperm-specific chromatin-modifying complex for gene silencing. Therefore, the two female gametes have evolved their own signaling pathways. Intriguingly, second-pollen-tube attraction induced by half-successful Fertilization allowed the ovules to complete Double Fertilization, producing a genetically distinct embryo and endosperm. We thus propose that each female gamete independently determines second-pollen-tube avoidance to maximize reproductive fitness in flowering plants.

  • Double Fertilization on the move.
    Current Opinion in Plant Biology, 2011
    Co-Authors: Yuki Hamamura, Shiori Nagahara, Tetsuya Higashiyama
    Abstract:

    Double Fertilization is a flowering plant mechanism whereby two immotile sperm cells fertilize two different female gametes. One of the two sperm cells fertilizes the egg cell to produce the embryo and the other fertilizes the central cell to produce the endosperm. Despite the biological and agricultural significance of Double Fertilization, the mechanism remains largely unknown owing to difficulties associated with the embedded structure of female gametes in the maternal tissue. However, molecular genetic approaches combined with novel live-cell imaging techniques have begun to clarify the actual behavior of the sperm cells, which is different from that described by previous hypotheses. In this review article, we discuss the mechanism of Double Fertilization based on the dynamics of the two sperm cells in Arabidopsis.

Ueli Grossniklaus - One of the best experts on this subject based on the ideXlab platform.

  • polyspermy produces tri parental seeds in maize
    Current Biology, 2017
    Co-Authors: Ueli Grossniklaus
    Abstract:

    In flowering plants, two pairs of gametes participate in Double Fertilization. One of the two sperm delivered by the pollen tube (PT) fuses with the egg cell to form the zygote, whereas the second unites with the central cell to produce the endosperm [1]. Most animal species prevent polyspermy through a transient, fast block established by the depolarization of the egg membrane within milliseconds after encountering the first sperm, followed by a slow block generated through enzymatic changes in the extracellular matrix surrounding the egg [2]. Although in vitro Fertilization experiments suggest that the maize zygote starts cell wall deposition within 30 seconds after fusion with a sperm [3], thereby preventing further Fertilization events, it is unknown whether plant gametes prevent polyspermy by a fast block. Here, using a genetic approach, the absence of a fast block preventing polyspermy in the maize central cell is demonstrated. A putative polyspermy event involving the egg indicates the existence of tri-parental individuals, which may provide an alternative route to polyploidy, distinct from the one involving unreduced gametes.

  • a calcium dialog mediated by the feronia signal transduction pathway controls plant sperm delivery
    Developmental Cell, 2014
    Co-Authors: Quy A Ngo, Hannes Vogler, Dmytro Lituiev, Anna Nestorova, Ueli Grossniklaus
    Abstract:

    Sperm delivery for Double Fertilization of flowering plants relies on interactions between the pollen tube (PT) and two synergids, leading to programmed cell death (PCD) of the PT and one synergid. The mechanisms underlying the communication among these cells during PT reception is unknown. We discovered that the synergids control this process by coordinating their distinct calcium signatures in response to the calcium dynamics and growth behavior of the PT. Induced and spontaneous aberrant calcium responses in the synergids abolish the two coordinated PCD events. Components of the FERONIA (FER) signaling pathway are required for initiating and modulating these calcium responses and for coupling the PCD events. Intriguingly, the calcium signatures are interchangeable between the two synergids, implying that their fates of death and survival are determined by reversible interactions with the PT. Thus, complex intercellular interactions involving a receptor kinase pathway and calcium-mediated signaling control sperm delivery in plants.

  • egg cell secreted ec1 triggers sperm cell activation during Double Fertilization
    Science, 2012
    Co-Authors: Stefanie Sprunck, Ueli Grossniklaus, Svenja Rademacher, Frank Vogler, Jacqueline Gheyselinck, Thomas Dresselhaus
    Abstract:

    Double Fertilization is a defining feature of flowering plants and involves two nonmotile male gametes (sperm cells) and two female gametes (egg cell and central cell). Both Fertilization events are necessary for reproductive success. It is not clear how flowering plants ensure the reliable and on-time fusion of the two pairs of gametes, while preventing polyspermy. Sprunck et al. (p. [1093][1]; see the Perspective by [Snell][2] ) now show that gamete interactions in Arabidopsis depend on small cysteine-rich EGG CELL 1 (EC1) proteins that accumulate in storage vesicles of the egg cell and that are released during sperm-egg interaction. EC1 peptides trigger the delivery of a fusogen to the sperm cell surface. An intercellular link connects the two sperm cells throughout the gamete fusion process and could play a role in preventing the spontaneous fusion of activated sperm cells. [1]: /lookup/doi/10.1126/science.1223944 [2]: /lookup/doi/10.1126/science.1231259

  • egg cell secreted ec1 triggers sperm cell activation during Double Fertilization
    Science, 2012
    Co-Authors: Stefanie Sprunck, Ueli Grossniklaus, Svenja Rademacher, Frank Vogler, Jacqueline Gheyselinck, Thomas Dresselhaus
    Abstract:

    Double Fertilization is the defining characteristic of flowering plants. However, the molecular mechanisms regulating the fusion of one sperm with the egg and the second sperm with the central cell are largely unknown. We show that gamete interactions in Arabidopsis depend on small cysteine-rich EC1 (EGG CELL 1) proteins accumulating in storage vesicles of the egg cell. Upon sperm arrival, EC1-containing vesicles are exocytosed. The sperm endomembrane system responds to exogenously applied EC1 peptides by redistributing the potential gamete fusogen HAP2/GCS1 (HAPLESS 2/GENERATIVE CELL SPECIFIC 1) to the cell surface. Furthermore, Fertilization studies with ec1 quintuple mutants show that successful male-female gamete interactions are necessary to prevent multiple-sperm cell delivery. Our findings provide evidence that mutual gamete activation, regulated exocytosis, and sperm plasma membrane modifications govern flowering plant gamete interactions.

  • molecular characterization of the glauce mutant a central cell specific function is required for Double Fertilization in arabidopsis
    The Plant Cell, 2012
    Co-Authors: Yehoram Leshem, Ueli Grossniklaus, Cameron Johnson, Samuel E Wuest, Xiaoya Song, Quy A Ngo, Venkatesan Sundaresan
    Abstract:

    Double Fertilization of the egg cell and the central cell by two sperm cells, resulting in the formation of the embryo and the endosperm, respectively, is a defining characteristic of flowering plants. The Arabidopsis thaliana female gametophytic mutant glauce (glc) can exhibit embryo development without any endosperm. Here, we show that in glc mutant embryo sacs one sperm cell successfully fuses with the egg cell but the second sperm cell fails to fuse with the central cell, resulting in single Fertilization. Complementation studies using genes from the glc deletion interval identified an unusual genomic locus having homology to BAHD (for BEAT, AHCT, HCBT, and DAT) acyl-transferases with dual transcription units and alternative splicing that could rescue the sterility defect of glc. Expression of these transcripts appears restricted to the central cell, and expression within the central cell is sufficient to restore fertility. We conclude that the central cell actively promotes its own Fertilization by the sperm cell through a signaling mechanism involving products of At1g65450. Successful Fertilization of the egg cell is not blocked in the glc mutant, suggesting that evolution of Double Fertilization in flowering plants involved acquisition of specific functions by the central cell to enable its role as a second female gamete.

Frederic Berger - One of the best experts on this subject based on the ideXlab platform.

  • live cell imaging reveals the dynamics of two sperm cells during Double Fertilization in arabidopsis thaliana
    Current Biology, 2011
    Co-Authors: Yuki Hamamura, Chieko Saito, Daisuke Kurihara, Chie Awai, Atsushi Miyawaki, Tsuyoshi Nakagawa, Masahiro M Kanaoka, Narie Sasaki, Akihiko Nakano, Frederic Berger
    Abstract:

    Flowering plants have evolved a unique reproductive process called Double Fertilization, whereby two dimorphic female gametes are fertilized by two immotile sperm cells conveyed by the pollen tube. The two sperm cells are arranged in tandem with a leading pollen tube nucleus to form the male germ unit and are placed under the same genetic controls. Genes controlling Double Fertilization have been identified, but whether each sperm cell is able to fertilize either female gamete is still unclear. The dynamics of individual sperm cells after their release in the female tissue remain largely unknown. In this study, we photolabeled individual isomorphic sperm cells before their release and analyzed their fate during Double Fertilization in Arabidopsis thaliana. We found that sperm delivery was composed of three steps. Sperm cells were projected together to the boundary between the two female gametes. After a long period of immobility, each sperm cell fused with either female gamete in no particular order, and no preference was observed for either female gamete. Our results suggest that the two sperm cells at the front and back of the male germ unit are functionally equivalent and suggest unexpected cell-cell communications required for sperm cells to coordinate Double Fertilization of the two female gametes.

  • green love talks cell cell communication during Double Fertilization in flowering plants
    Aob Plants, 2011
    Co-Authors: Tomokazu Kawashima, Frederic Berger
    Abstract:

    BACKGROUND Flowering plant seeds originate from a unique Double-Fertilization event, which involves two sperm cells and two female gametes, the egg cell and the central cell. For many years our knowledge of mechanisms involved in angiosperm Fertilization remained minimal. It was obvious that several signals were required to explain how the male gametes are delivered inside the maternal reproductive tissues to the two female gametes but their molecular nature remained unknown. The difficulties in imaging the Double-Fertilization process prevented the identification of the mode of sperm cell delivery. It was believed that the two sperm cells were not functionally equivalent. SCOPE We review recent studies that have significantly improved our understanding of the early steps of Double Fertilization. The attractants of the pollen tube have been identified as small proteins produced by the synergid cells that surround the egg cell. Genetic studies have identified the signalling pathways required for the release of male gametes from the pollen tube. High-resolution imaging of the trajectory of the two male gametes showed that their transport does not involve the synergid cells directly and that isomorphic male gametes are functionally equivalent. We also outline major outstanding issues in the field concerned with the barrier against polyspermy, gamete recognition and mechanisms that prevent interspecies crosses.

  • the two male gametes share equal ability to fertilize the egg cell in arabidopsis thaliana
    Current Biology, 2009
    Co-Authors: Mathieu Ingouff, Thomas Dresselhaus, Stefanie Sprunck, Tadashi Sakata, Frederic Berger
    Abstract:

    Summary The seed of a flowering plant develops from an ovule containing two distinct female gametes — the egg cell and the central cell — that are fertilized by a pair of non-motile sperm cells conveyed by the pollen tube. With a few exceptions [1], the two sperm cells, derived from a symmetrical mitosis, are isomorphic and seem to express a similar gene repertoire [2]. Since the discovery of Double Fertilization in flowering plants at the end of the 19th century, it has been a long standing question whether the two sperm cells are functionally equivalent, that is, whether they are capable of fertilizing the egg cell and the central cell in equal measure.

  • Double Fertilization caught in the act
    Trends in Plant Science, 2008
    Co-Authors: Frederic Berger, Yuki Hamamura, Mathieu Ingouff, Tetsuya Higashiyama
    Abstract:

    In flowering plants, Fertilization is unique because it involves two pairs of male and female gametes, a process known as Double Fertilization. Here, we provide an overview of the field and a detailed review of the outstanding recent advances, including in vivo imaging of Double Fertilization and the identification of a signaling pathway controlling the release of the male gametes and of a protein involved in gamete membrane fusion. These recent results are stepping stones for further research; our knowledge of Double Fertilization is expanding as newly discovered molecular pathways are explored and new mutants are characterized. Controlling plant Fertilization is essential for seed production, and molecular understanding of Double Fertilization will provide the tools to improve crops and breeding programs.

  • the female gametophyte and the endosperm control cell proliferation and differentiation of the seed coat in arabidopsis
    The Plant Cell, 2006
    Co-Authors: Mathieu Ingouff, Pauline E Jullien, Frederic Berger
    Abstract:

    Double Fertilization of the female gametophyte produces the endosperm and the embryo enclosed in the maternal seed coat. Proper seed communication necessitates exchanges of signals between the zygotic and maternal components of the seed. However, the nature of these interactions remains largely unknown. We show that Double Fertilization of the Arabidopsis thaliana female gametophyte rapidly triggers sustained cell proliferation in the seed coat. Cell proliferation and differentiation of the seed coat occur in autonomous seeds produced in the absence of Fertilization of the multicopy suppressor of ira1 (msi1) mutant. As msi1 autonomous seeds mostly contain autonomous endosperm, our results indicate that the developing endosperm is sufficient to enhance cell proliferation and differentiation in the seed coat. We analyze the effect of autonomous proliferation in the retinoblastoma-related1 (rbr1) female gametophyte on seed coat development. In contrast with msi1, supernumerary nuclei inrbr1 female gametophytes originate mainly from the endosperm precursor lineage but do not express an endosperm fate marker. In addition, defects of the rbr1 female gametophyte also reduce cell proliferation in the ovule integuments before Fertilization and prevent further differentiation of the seed coat. Our data suggest that coordinated development of the seed components relies on interactions before Fertilization between the female gametophyte and the surrounding maternal ovule integuments and after Fertilization between the endosperm and the seed coat.

Ravishankar Palanivelu - One of the best experts on this subject based on the ideXlab platform.

  • a fruitful journey pollen tube navigation from germination to Fertilization
    Annual Review of Plant Biology, 2019
    Co-Authors: Mark A Johnson, Jeffrey F Harper, Ravishankar Palanivelu
    Abstract:

    In flowering plants, pollen tubes undergo tip growth to deliver two nonmotile sperm to the ovule where they fuse with an egg and central cell to achieve Double Fertilization. This extended journey ...

  • a fruitful journey pollen tube navigation from germination to Fertilization
    Annual Review of Plant Biology, 2019
    Co-Authors: Mark A Johnson, Jeffrey F Harper, Ravishankar Palanivelu
    Abstract:

    In flowering plants, pollen tubes undergo tip growth to deliver two nonmotile sperm to the ovule where they fuse with an egg and central cell to achieve Double Fertilization. This extended journey involves rapid growth and changes in gene activity that manage compatible interactions with at least seven different cell types. Nearly half of the genome is expressed in haploid pollen, which facilitates genetic analysis, even of essential genes. These unique attributes make pollen an ideal system with which to study plant cell-cell interactions, tip growth, cell migration, the modulation of cell wall integrity, and gene expression networks. We highlight the signaling systems required for pollen tube navigation and the potential roles of Ca2+ signals. The dynamics of pollen development make sexual reproduction highly sensitive to heat stress. Understanding this vulnerability may generate strategies to improve seed crop yields that are under threat from climate change.

  • pathfinding in angiosperm reproduction pollen tube guidance by pistils ensures successful Double Fertilization
    Wiley Interdisciplinary Reviews-Developmental Biology, 2012
    Co-Authors: Ravishankar Palanivelu, Tatsuya Tsukamoto
    Abstract:

    Sexual reproduction in flowering plants is unique in multiple ways. Distinct multicellulargametophytescontaineitherapairofimmotile,haploidmalegametes (sperm cells) or a pair of female gametes (haploid egg cell and homodiploid central cell). After pollination, the pollen tube, a cellular extension of the male gametophyte, transports both male gametes at its growing tip and delivers them to the female gametes to affect Double Fertilization. The pollen tube travels a long path and sustains its growth over a considerable amount of time in the female reproductive organ (pistil) before it reaches the ovule, which houses the female gametophyte. The pistil facilitates the pollen tube’s journey by providing multiple, stage-specific, nutritional, and guidance cues along its path. The pollen tube interacts with seven different pistil cell types prior to completing its journey. Consequently, the pollen tube has a dynamic gene expression program allowing it to continuously reset and be receptive to multiple pistil signals as it migrates through the pistil. Here, we review the studies, including several significant recent advances, that led to a better understanding of the multitude of cues generated by the pistil tissues to assist the pollen tube in delivering the sperm cells to the female gametophyte. We also highlight the outstanding questions, draw attention to opportunities created by recent advances and point to approaches that could be undertaken to unravel the molecular mechanisms underlying pollen tube‐pistil

  • pathfinding in angiosperm reproduction pollen tube guidance by pistils ensures successful Double Fertilization
    Wiley Interdisciplinary Reviews-Developmental Biology, 2012
    Co-Authors: Ravishankar Palanivelu, Tatsuya Tsukamoto
    Abstract:

    Sexual reproduction in flowering plants is unique in multiple ways. Distinct multicellular gametophytes contain either a pair of immotile, haploid male gametes (sperm cells) or a pair of female gametes (haploid egg cell and homodiploid central cell). After pollination, the pollen tube, a cellular extension of the male gametophyte, transports both male gametes at its growing tip and delivers them to the female gametes to affect Double Fertilization. The pollen tube travels a long path and sustains its growth over a considerable amount of time in the female reproductive organ (pistil) before it reaches the ovule, which houses the female gametophyte. The pistil facilitates the pollen tube's journey by providing multiple, stage-specific, nutritional, and guidance cues along its path. The pollen tube interacts with seven different pistil cell types prior to completing its journey. Consequently, the pollen tube has a dynamic gene expression program allowing it to continuously reset and be receptive to multiple pistil signals as it migrates through the pistil. Here, we review the studies, including several significant recent advances, that led to a better understanding of the multitude of cues generated by the pistil tissues to assist the pollen tube in delivering the sperm cells to the female gametophyte. We also highlight the outstanding questions, draw attention to opportunities created by recent advances and point to approaches that could be undertaken to unravel the molecular mechanisms underlying pollen tube-pistil interactions.

  • a role for lorelei a putative glycosylphosphatidylinositol anchored protein in arabidopsis thaliana Double Fertilization and early seed development
    Plant Journal, 2010
    Co-Authors: Tatsuya Tsukamoto, Yuan Qin, Yiding Huang, Damayanthi Dunatunga, Ravishankar Palanivelu
    Abstract:

    In plants, Double Fertilization requires successful sperm cell delivery into the female gametophyte followed by migration, recognition and fusion of the two sperm cells with two female gametes. We isolated a null allele (lre-5) of LORELEI, which encodes a putative glycosylphosphatidylinositol (GPI)-anchored protein implicated in reception of the pollen tube by the female gametophyte. Although most lre-5 female gametophytes do not allow pollen tube reception, in those that do, early seed development is delayed. A fraction of lre-5/lre-5 seeds underwent abortion due to defect(s) in the female gametophyte. The aborted seeds contained endosperm but no zygote/embryo, reminiscent of autonomous endosperm development in the pollen tube reception mutants scylla and sirene. However, unpollinated lre-5/lre-5 ovules did not initiate autonomous endosperm development and endosperm development in aborted seeds began after central cell Fertilization. Thus, the egg cell probably remained unfertilized in aborted lre-5/lre-5 seeds. The lre-5/lre-5 ovules that remain undeveloped due to defective pollen tube reception did not induce synergid degeneration and repulsion of supernumerary pollen tubes. In ovules, LORELEI is expressed during pollen tube reception, Double Fertilization and early seed development. Null mutants of LORELEI-like-GPI-anchored protein 1 (LLG1), the closest relative of LORELEI among three Arabidopsis LLG genes, are fully fertile and did not enhance reproductive defects in lre-5/lre-5 pistils, suggesting that LLG1 function is not redundant with that of LORELEI in the female gametophyte. Our results show that, besides pollen tube reception, LORELEI also functions during Double Fertilization and early seed development.