Abstract
In pollen tubes, cytoskeleton proteins are involved in many aspects of pollen germination and growth, from the transport of sperm cells to the asymmetrical distribution of organelles to the deposition of cell wall material. These activities are based on the dynamics of the cytoskeleton. Changes to both actin filaments and microtubules are triggered by specific proteins, resulting in different organization levels suitable for the different functions of the cytoskeleton. Transglutaminases are enzymes ubiquitous in all plant organs and cell compartments. They catalyze the post-translational conjugation of polyamines to different protein targets, such as the cytoskeleton. Transglutaminases are suggested to have a general role in the interaction between pollen tubes and the extracellular matrix during fertilization and a specific role during the self-incompatibility response. In such processes, the activity of transglutaminases is enhanced, leading to the formation of cross-linked products (including aggregates of tubulin and actin). Consequently, transglutaminases are suggested to act as regulators of cytoskeleton dynamics. The distribution of transglutaminases in pollen tubes is affected by both membrane dynamics and the cytoskeleton. Transglutaminases are also secreted in the extracellular matrix, where they may take part in the assembly and/or strengthening of the pollen tube cell wall.
Highlights
In pollen tubes, cytoskeleton proteins are involved in many aspects of pollen germination and growth, from the transport of sperm cells to the asymmetrical distribution of organelles to the deposition of cell wall material
Recent studies suggest that transglutaminases (TGs; EC 2.3.2.13) (TGase) is a relatively critical element in the growth process of pollen tubes
TGase of membranes may be somewhat involved in the process of cell wall structuring in order to make it more or less elastic, depending on the medium that the pollen tube has to cross
Summary
The reproductive success of seed plants is performed and based on the invention of the pollen tube, an extension of the pollen grain that is produced under favorable conditions and that allows the sperm cells to move from the male gametophyte towards the female one. The fact that pollen tubes grow exclusively in a specific domain (the tip) following a precise direction suggested that pollen tubes might be compared to rhizodermis trichoblastic cells, and to nerve cells of animals [1] Such a comparison is clearly forced and may stress the similarities between two very different cell types. Two types of cell wall components are delivered to the tip domain: pectins/hemicelluloses and enzymes required for the membrane-localized synthesis of callose and cellulose. Close to the growth domain, callose and (to a lesser extent) cellulose are deposited by their plasma membrane-localized enzymes [5] This process reinforces and stabilizes the pollen tube cell wall. Secretory vesicles are likely to deliver proteins and other molecules required for regulating the growth process These include receptors, ion channels, plasma membrane-associated G proteins and lipid-modifying enzymes. Accepted models indicate that the balance between pectin composition and turgor pressure constitutes the ―motor‖ that promotes tube growth, while the molecular network in the tip domain represents the ―driver‖ that either guides the growth or regulates its rate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
