Abstract
Pollen germination and pollen tube growth are important biological events in the sexual reproduction of higher plants, during which a large number of vesicle trafficking and membrane fusion events occur. When secretory vesicles are transported via the F-actin network in proximity to the apex of the pollen tube, the secretory vesicles are tethered and fused to the plasma membrane by tethering factors and SNARE proteins, respectively. The coupling and uncoupling between the vesicle membrane and plasma membrane are also regulated by dynamic cytoskeleton, proteins, and signaling molecules, including small G proteins, calcium, and PIP2. In this review, we focus on the current knowledge regarding secretory vesicle delivery, tethering, and fusion during pollen germination and tube growth and summarize the progress in research on how regulators and signaling molecules participate in the above processes.
Highlights
In seed plants, the production of seeds depends on double fertilization
We focus on the process of secretory vesicle directional targeting the PM, which involves vesicle delivery, tethering, and fusion during pollen germination and tip growth, as well as on the different regulators involved, such as some key signaling proteins and other molecules
ROP1 activates RIC4 to promote actin assembly, change the arrangement of the MF skeleton, and induce the accumulation and transport of vesicles to the tip region (Gu et al, 2005; Lee et al, 2008). These results indicate that ROP1 is involved in vesicle transport through regulation of MFs in pollen tubes
Summary
The production of seeds depends on double fertilization. Mature pollen grains are tri-cellular and composed of two small sperm cells and a large vegetative cell in Arabidopsis. Pollen germination and pollen tube elongation form the whole process by which polarity is established and maintained In this process, many cell wall materials, such as pectins and cellulose, are contained as cargo in vesicles with an average diameter of 0.182 μm (Ketelaar et al, 2008; Chebli et al, 2012). Many cell wall materials, such as pectins and cellulose, are contained as cargo in vesicles with an average diameter of 0.182 μm (Ketelaar et al, 2008; Chebli et al, 2012) These vesicles arise from the Golgi and trans-Golgi network (TGN) and are directionally transported toward and fused with the plasma membrane (PM) at polar exocytosis sites to enable the membrane extension and sustained synthesis of new cell wall material (Wang et al, 2016; Zheng et al, 2018; Grebnev et al, 2020; Guo and Yang, 2020)
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