Description
- Abstract:
- In sexual reproduction, fusion of haploid sperm and egg cells (gametes) are required to produce a unique diploid individual that represents the next generation. Despite the conservation of this process across various eukaryotes, mechanisms responsible for gamete fusion have not been elucidated in any system. In flowering plants, two gamete fusion events are required to produce a seed, a product that is essential for both propagation of plant species and agriculture. In this system, two immotile sperm cells are delivered to the site of gamete fusion by a tip-growing cell called a pollen tube. Once the pollen tube bursts and releases the sperm cells, one fuses with the egg cell giving rise to the embryo, and the other fuses with the central cell, giving rise to the endosperm that provides nutrients to the developing embryo. If only one pollen tube targets each ovule, only the two required sperm for fertilization are deposited and additional pollen tubes are repelled. This regulation prevents too many sperm from being delivered to the site of fusion, an event that can lead to multiple sperm cells fusing with a single egg cell and detrimental developmental defects. An experimental inroad into the process of gamete fusion and sperm delivery is HAP2, a sperm-specific gene required for gamete fusion in several diverged species including the flowering plant Arabidopsis. Here, it is demonstrated using live-cell imaging that when hap2 mutant sperm incapable of gamete fusion are delivered, additional pollen tubes are attracted at a high rate in an effort to deposit functional sperm, an event rarely seen in wild type. This observation shows that flowering plants have coupled successful gamete fusion with sperm cell delivery to enhance reproductive success by ensuring that every ovule receives functional sperm. In addition, we show that HAP2 is sufficient to rescue fusion in naïve Arabidopsis sperm cells that are unable to fuse with either the egg cell or the central cell. Using a forward genetic screen we also identified several novel candidate genes expressed in both male and female cells that might interact with HAP2 to mediate fusion.
- Notes:
- Thesis (Ph.D. -- Brown University (2014)
Access Conditions
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Citation
Beale, Kristin M.,
"Coupling Gamete Fusion with Sperm Cell Delivery Maximizes Reproductive Success in Flowering Plants"
(2014).
Molecular Biology, Cell Biology, and Biochemistry Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0ZC816P
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Molecular Biology, Cell Biology, and Biochemistry Theses and Dissertations
Theses and Dissertations for the Molecular Biology, Cell Biology, and Biochemistry department....