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International Journal of Molecular... Jan 2019Pollen is the male gametophyte of higher plants. Its major function is to deliver sperm cells to the ovule to ensure successful fertilization. During this process, many... (Review)
Review
Pollen is the male gametophyte of higher plants. Its major function is to deliver sperm cells to the ovule to ensure successful fertilization. During this process, many interactions occur among pollen tubes and pistil cells and tissues, and calcium ion (Ca) dynamics mediate these interactions among cells to ensure that pollen reaches the embryo sac. Although the precise functions of Ca dynamics in the cells are unknown, we can speculate about its roles on the basis of its spatial and temporal characteristics during these interactions. The results of many studies indicate that calcium is a critical element that is strongly related to pollen germination and pollen tube growth.
Topics: Calcium; Flowers; Germination; Plant Development; Plant Physiological Phenomena; Pollen; Pollen Tube
PubMed: 30669423
DOI: 10.3390/ijms20020420 -
Molecular Plant Jul 2013Pollen tubes elongate rapidly at their tips through highly polarized cell growth known as tip growth. Tip growth requires intensive exocytosis at the tip, which is... (Review)
Review
Pollen tubes elongate rapidly at their tips through highly polarized cell growth known as tip growth. Tip growth requires intensive exocytosis at the tip, which is supported by a dynamic cytoskeleton and vesicle trafficking. Several signaling pathways have been demonstrated to coordinate pollen tube growth by regulating cellular activities such as actin dynamics, exocytosis, and endocytosis. These signaling pathways crosstalk to form a signaling network that coordinates the cellular processes required for tip growth. The homeostasis of key signaling molecules is critical for the proper elongation of the pollen tube tip, and is commonly fine-tuned by positive and negative regulations. In addition to the major signaling pathways, emerging evidence implies the roles of other signals in the regulation of pollen tube growth. Here we review and discuss how these signaling networks modulate the rapid growth of pollen tubes.
Topics: Endocytosis; Exocytosis; Feedback, Physiological; Homeostasis; Pollen Tube; Signal Transduction
PubMed: 23873928
DOI: 10.1093/mp/sst070 -
Male-female crosstalk during pollen germination, tube growth and guidance, and double fertilization.Molecular Plant Jul 2013Sperm cells of flowering plants are non-motile and thus require transportation to the egg apparatus via the pollen tube to execute double fertilization. During its... (Review)
Review
Sperm cells of flowering plants are non-motile and thus require transportation to the egg apparatus via the pollen tube to execute double fertilization. During its journey, the pollen tube interacts with various sporophytic cell types that support its growth and guide it towards the surface of the ovule. The final steps of tube guidance and sperm delivery are controlled by the cells of the female gametophyte. During fertilization, cell-cell communication events take place to achieve and maximize reproductive success. Additional layers of crosstalk exist, including self-recognition and specialized processes to prevent self-fertilization and consequent inbreeding. In this review, we focus on intercellular communication between the pollen grain/pollen tube including the sperm cells with the various sporophytic maternal tissues and the cells of the female gametophyte. Polymorphic-secreted peptides and small proteins, especially those belonging to various subclasses of small cysteine-rich proteins (CRPs), reactive oxygen species (ROS)/NO signaling, and the second messenger Ca(2+), play center stage in most of these processes.
Topics: Fertilization; Germination; Ovule; Pollen Tube; Self-Incompatibility in Flowering Plants; Signal Transduction
PubMed: 23571489
DOI: 10.1093/mp/sst061 -
The International Journal of... 2020Professor Panchanan Maheshwari served as Professor and Head of the Department of Botany, University of Delhi, from 1950 to 1966 and built an internationally reputed... (Review)
Review
Professor Panchanan Maheshwari served as Professor and Head of the Department of Botany, University of Delhi, from 1950 to 1966 and built an internationally reputed School of integrated plant embryology. Studies carried out during and after Maheshwari's period from this School have enormously advanced our knowledge of the structural, developmental and functional aspects of embryological processes. This review covers studies carried out at the Delhi School on the developmental biology of dispersed pollen grains which operate from pollen dispersal from the anthers until pollen tubes discharge the male gametes in the embryo sac for fertilization. These events include pollen viability and vigour, pollen germination and pollen tube growth, structural details of the pistil relevant to pollen function, pollination and pollen-pistil interaction.
Topics: Developmental Biology; Flowers; Gene Expression Regulation, Plant; Germination; Plant Proteins; Pollen; Pollen Tube
PubMed: 32659021
DOI: 10.1387/ijdb.190166ks -
International Journal of Molecular... Nov 2018The angiosperm pollen tube delivers two sperm cells into the embryo sac through a unique growth strategy, named tip growth, to accomplish fertilization. A great deal of... (Review)
Review
The angiosperm pollen tube delivers two sperm cells into the embryo sac through a unique growth strategy, named tip growth, to accomplish fertilization. A great deal of experiments have demonstrated that actin bundles play a pivotal role in pollen tube tip growth. There are two distinct actin bundle populations in pollen tubes: the long, rather thick actin bundles in the shank and the short, highly dynamic bundles near the apex. With the development of imaging techniques over the last decade, great breakthroughs have been made in understanding the function of actin bundles in pollen tubes, especially short subapical actin bundles. Here, we tried to draw an overall picture of the architecture, functions and underlying regulation mechanism of actin bundles in plant pollen tubes.
Topics: Actin Cytoskeleton; Actins; Magnoliopsida; Microfilament Proteins; Plant Proteins; Pollen Tube
PubMed: 30469514
DOI: 10.3390/ijms19123710 -
The New Phytologist Jan 2018Occam's Razor suggests a new model of pollen tube tip growth based on a novel Hechtian oscillator that integrates a periplasmic arabinogalactan glycoprotein-calcium... (Review)
Review
Occam's Razor suggests a new model of pollen tube tip growth based on a novel Hechtian oscillator that integrates a periplasmic arabinogalactan glycoprotein-calcium (AGP-Ca ) capacitor with tip-localized AGPs as the source of tip-focussed cytosolic Ca oscillations: Hechtian adhesion between the plasma membrane and the cell wall of the growing tip acts as a piconewton force transducer that couples the internal stress of a rapidly growing wall to the plasma membrane. Such Hechtian transduction opens stretch-activated Ca channels and activates H -ATPase proton pump efflux that dissociates periplasmic AGP-Ca resulting in a Ca influx that activates exocytosis of wall precursors. Thus, a highly simplified pectic primary cell wall regulates its own synthesis by a Hechtian growth oscillator that regulates overall tip growth. By analogy with the three cryptic inscriptions of the classical Rosetta Stone, the Hechtian Hypothesis translates classical AGP function as a Ca capacitor, pollen tube guide and wall plasticizer into a simple but widely applicable model of tip growth. Even wider ramifications of the Hechtian oscillator may implicate AGPs in osmosensing or gravisensing and other tropisms, leading us yet further towards the Holy Grail of plant growth.
Topics: Cell Membrane; Galactans; Glycoproteins; Mechanotransduction, Cellular; Models, Biological; Pollen Tube
PubMed: 28990197
DOI: 10.1111/nph.14845 -
Annals of Botany Jul 2012Arabinogalactan proteins (AGPs) are complex proteoglycans of the cell wall found in the entire plant kingdom and in almost all plant organs. AGPs encompass a large group... (Review)
Review
BACKGROUND
Arabinogalactan proteins (AGPs) are complex proteoglycans of the cell wall found in the entire plant kingdom and in almost all plant organs. AGPs encompass a large group of heavily glycosylated cell-wall proteins which share common features, including the presence of glycan chains especially enriched in arabinose and galactose and a protein backbone particularly rich in hydroxyproline residues. However, AGPs also exhibit strong heterogeneities among their members in various plant species. AGP ubiquity in plants suggests these proteoglycans are fundamental players for plant survival and development.
SCOPE
In this review, we first present an overview of current knowledge and specific features of AGPs. A section devoted to major tools used to study AGPs is also presented. We then discuss the distribution of AGPs as well as various aspects of their functional properties in root tissues and pollen tubes. This review also suggests novel directions of research on the role of AGPs in the biology of roots and pollen tubes.
Topics: Cell Wall; Mucoproteins; Plant Proteins; Plant Roots; Plants; Pollen Tube; Tissue Distribution
PubMed: 22786747
DOI: 10.1093/aob/mcs143 -
International Journal of Molecular... Nov 2021In angiosperms, double fertilization requires pollen tubes to transport non-motile sperm to distant egg cells housed in a specialized female structure known as the... (Review)
Review
In angiosperms, double fertilization requires pollen tubes to transport non-motile sperm to distant egg cells housed in a specialized female structure known as the pistil, mediating the ultimate fusion between male and female gametes. During this journey, the pollen tube encounters numerous physical barriers that must be mechanically circumvented, including the penetration of the stigmatic papillae, style, transmitting tract, and synergid cells as well as the ultimate fusion of sperm cells to the egg or central cell. Additionally, the pollen tube must maintain structural integrity in these compact environments, while responding to positional guidance cues that lead the pollen tube to its destination. Here, we discuss the nature of these physical barriers as well as efforts to genetically and cellularly identify the factors that allow pollen tubes to successfully, specifically, and quickly circumnavigate them.
Topics: Cell Communication; Flowers; Pollen Tube; Pollination
PubMed: 34830110
DOI: 10.3390/ijms222212230 -
Biochimica Et Biophysica Acta Jul 2013Pollen tubes grow rapidly by very fast rates and reach extended lengths to bring about fertilization during plant reproduction. The pollen tube grows exclusively at its... (Review)
Review
Pollen tubes grow rapidly by very fast rates and reach extended lengths to bring about fertilization during plant reproduction. The pollen tube grows exclusively at its tip. Fundamental for such local, tip-focused growth are the presence of internal gradients and transmembrane fluxes of ions. Consequently, vegetative pollen tube cells are an excellent single cell model system to investigate cell biological processes of vesicle transport, cytoskeleton reorganization and regulation of ion transport. The second messenger Ca(2+) has emerged as a central and crucial modulator that not only regulates but also integrates the coordination each of these processes. In this review we reflect on recent advances in our understanding of the mechanisms of Ca(2+) function in pollen tube growth, focusing on its role in basic cellular processes such as control of cell growth, vesicular transport and intracellular signaling by localized gradients of second messengers. In particular we discuss new insights into the identity and role of Ca(2+) conductive ion channels and present experimental addressable hypotheses about their regulation. This article is part of a Special Issue entitled:12th European Symposium on Calcium.
Topics: Calcium; Plants; Pollen; Pollen Tube; Pollination
PubMed: 23072967
DOI: 10.1016/j.bbamcr.2012.10.009 -
Molecular Plant Mar 2017Maize is the most important agricultural crop used for food, feed, and biofuel as well as a raw material for industrial products such as packaging material. To increase... (Review)
Review
Maize is the most important agricultural crop used for food, feed, and biofuel as well as a raw material for industrial products such as packaging material. To increase yield and to overcome hybridization barriers, studies of maize gamete development, the pollen tube journey, and fertilization mechanisms were initiated more than a century ago. In this review, we summarize and discuss our current understanding of the regulatory components for germline development including sporogenesis and gametogenesis, the progamic phase of pollen germination and pollen tube growth and guidance, as well as fertilization mechanisms consisting of pollen tube arrival and reception, sperm cell release, fusion with the female gametes, and egg cell activation. Mechanisms of asexual seed development are not considered here. While only a few molecular players involved in these processes have been described to date and the underlying mechanisms are far from being understood, maize now represents a spearhead of reproductive research for all grass species. Recent development of essentially improved transformation and gene-editing systems may boost research in this area in the near future.
Topics: Fertilization; Ovule; Plant Proteins; Pollen Tube; Zea mays
PubMed: 28267957
DOI: 10.1016/j.molp.2017.01.012