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- Double fertilization – caught in the act
Trends in Plant Science, Volume 13, Issue 8, 1 August 2008, Pages 437-443
Frédéric Berger, Yuki Hamamura, Mathieu Ingouff and Tetsuya Higashiyama
AbstractIn flowering plants, fertilization is unique because it involves two pairs of male and female gametes, a process known as double fertilization. Here, we provide an overview of the field and a detailed review of the outstanding recent advances, including in vivo imaging of double fertilization and the identification of a signaling pathway controlling the release of the male gametes and of a protein involved in gamete membrane fusion. These recent results are stepping stones for further research; our knowledge of double fertilization is expanding as newly discovered molecular pathways are explored and new mutants are characterized. Controlling plant fertilization is essential for seed production, and molecular understanding of double fertilization will provide the tools to improve crops and breeding programs.
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- A Central Role for P48/45 in Malaria Parasite Male Gamete Fertility
Cell, Volume 104, Issue 1, 12 January 2001, Pages 153-164
Melissa R. van Dijk, Chris J. Janse, Joanne Thompson, Andrew P. Waters, Joanna A.M. Braks, Huub J. Dodemont, Henk G. Stunnenberg, Geert-Jan van Gemert, Robert W. Sauerwein and Wijnand Eling
SummaryFertilization and zygote development are obligate features of the malaria parasite life cycle and occur during parasite transmission to mosquitoes. The surface protein PFS48/45 is expressed by male and female gametes of Plasmodium falciparum and PFS48/45 antibodies prevent zygote development and transmission. Here, gene disruption was used to show that Pfs48/45 and the ortholog Pbs48/45 from a rodent malaria parasite P. berghei play a conserved and important role in fertilization. p48/45− parasites had a reduced capacity to produce oocysts in mosquitoes due to greatly reduced zygote formation. Unexpectedly, only male gamete fertility of p48/45− parasites was affected, failing to penetrate otherwise fertile female gametes. P48/45 is shown to be a surface protein of malaria parasites with a demonstrable role in fertilization.
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- Is HAP2-GCS1 an ancestral gamete fusogen?
Trends in Cell Biology, Volume 20, Issue 3, 1 March 2010, Pages 134-141
Julian L. Wong and Mark A. Johnson
AbstractEukaryotes employ a diversity of strategies to ensure that gametes come together, but the cellular climax is less varied: gamete plasma membranes must fuse to allow the combination of parental genomes. Recent studies of HAP2-GCS1, a sex-restricted transmembrane protein found in genomes representing all major eukaryotic taxa except fungi, suggest that a broad array of eukaryotic organisms could share a common mechanism for gamete fusion. Plant, protozoan, and algal gametes carrying loss-of-function mutations in HAP2-GCS1 fail to fuse with their complements. We propose that HAP2-GCS1 is a crucial component of an ancient mechanism that mediates the fusion of gamete plasma membranes and could have been a key early innovation in the evolution of sexual reproduction.
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Copyright © 2001 Elsevier Science Ltd All rights reserved.
Trends in Ecology & Evolution, Volume 16, Issue 10, 571-579, 1 October 2001
The uncertain evolution of the sexes
What forces gave rise to the evolution of the size difference between sperm and eggs? For many years, it has been all but accepted wisdom that the answer was laid out by Parker et al. However, their model requires an unusual and unverified assumption regarding the relationship between zygote size and fitness. Although the first phylogenetically controlled test of the comparative predictions of the model is consistent, the results have a simple alternative interpretation. Furthermore, recent work has formalized different theoretical frameworks that require less unusual assumptions. These postulate, for example, that, under sperm limitation, a larger egg will have an increased chance of being fertilized, either because its own mass offers a larger target for sperm or because larger eggs can produce a greater quantity of attraction pheromone. Other frameworks either point to small sperm preventing transmission of cytoplasmic symbionts and/or organelles or having a motility advantage. At present, however, no model is capable of offering a universal explanation.