Abstract
In flowering plants, sexual reproduction involves a double fertilization event, which is facilitated by the delivery of two non-motile sperm cells to the ovule by the pollen tube. Pollen tube growth occurs exclusively at the tip and is extremely rapid. It strictly depends on an intact actin cytoskeleton, and is therefore an excellent model for uncovering the molecular mechanisms underlying dynamic actin cytoskeleton remodeling. There has been a long-term debate about the organization and dynamics of actin filaments within the apical and subapical regions of pollen tube tips. By combining state-of-the-art live-cell imaging with the usage of mutants which lack different actin-binding proteins, our understanding of the origin, spatial organization, dynamics and regulation of actin filaments within the pollen tube tip has greatly improved. In this review article, we will summarize the progress made in this area.
Highlights
In flowering plants, sexual reproduction involves a double fertilization event, which is facilitated by the delivery of two non-motile sperm cells to the ovule by the pollen tube
Our understanding of how actin performs its function has been hindered by the lack of a unified view about the origin, spatial organization and dynamics of actin filaments within the growth domain of pollen tubes
It is clear that actin filaments are continuously polymerized from the plasma membrane at the extreme apex of pollen tubes during their extension, which answers the longstanding question about whether actin filaments exist at the extreme apex
Summary
Received: 07 October 2020 Accepted: 13 November 2020 Published: 03 December 2020. Citation: Xu Y and Huang S (2020) Control of the Actin Cytoskeleton Within Apical and Subapical Regions of Pollen Tubes. Sexual reproduction involves a double fertilization event, which is facilitated by the delivery of two non-motile sperm cells to the ovule by the pollen tube. There has been a long-term debate about the organization and dynamics of actin filaments within the apical and subapical regions of pollen tube tips. Similar to the filamentous protonemata of mosses and the root hairs of high plants, pollen tubes are tip-growing cells, with growth strictly occurring within the apical region (Rounds and Bezanilla, 2013). The rapidity of pollen tube growth greatly shortens the time required for the delivery of sperm cells to the ovules, favoring fertilization. We will describe our current understanding of the organization, dynamics and regulation of the actin cytoskeleton in pollen tubes, with the focus on the apical and subapical regions
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