<p>Plants are
used as a primary food source by humans. Some plants produce edible roots or
leaves, but most crops used today are grown to harvest their nutrient-rich
seeds which are a product of double fertilization in flowering plants. </p>
<p>Cell-cell
recognition, adhesion, and fusion are widespread phenomena in many biological
processes, where fertilization is an exemplary process. Many players have been
identified to mediate sperm-egg fusion in both animals and plants.
Interestingly several of these components were shown to be structurally and
functionally conserved across kingdoms. In animals Tetraspanins act as
facilitators of sperm-egg fusion. Tetraspanins are known to associate in
clusters in the plasma membrane of cells, where they recruit diverse signaling proteins,
forming the so called Tetraspanin-enriched microdomains (TEMs). TEMs are
therefore recognized as major signaling platforms mediating specific cellular
processes in the plasma membrane of cells. Two <i>Arabidopsis</i>-expressed
tetraspanins, <i>TET11</i> and <i>TET12</i>, are highly expressed in the sperm
cells (SCs), however their function in fertilization are unknown. Using
fluorescence microscopy, we quantified the expression of TETs in SCs and found
evidence for the existence of a Tetraspanin-enriched microdomain (TEM) at the SC-SC
adhesion interface. Sperm cell factors which are necessary for fertilization
were found to accumulate at the TEM, suggesting that plant SC TEMs may function
as protective platforms for fertilization factors. Sperm-expressed TETs
directly interact with members of a novel, plant-specific family of unknown
proteins, <i>DMP8/9</i>. DMP8/9 function as negative regulators of SC-SC
adhesion and are required for double fertilization. Structural and functional
analysis suggest that these two proteins may perform unique functions as
membrane remodelers in SCs. In addition, we provide evidence of a new GEX2 function
as a SC-SC adhesion factor and potential partner of TET-DMP complexes at the
SC-SC interface.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12749258 |
| Date | 03 August 2020 |
| Creators | Ryan L Hockemeyer (9193580) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Functional_and_Structural_Characterization_of_TET_JANUS_Signaling_Complexes_in_A_Thaliana_Sperm_Cells/12749258 |
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