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First published online September 4, 2009; 10.1104/pp.109.144204 Plant Physiology 151:1390-1400 (2009) © 2009 American Society of Plant Biologists OPEN ACCESS ARTICLE
Expressing the Diphtheria Toxin A Subunit from the HAP2(GCS1) Promoter Blocks Sperm Maturation and Produces Single Sperm-Like Cells Capable of Fertilization1,[W],[OA]Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island 02912
After meiosis, the male germline of flowering plants undergoes two mitoses, producing two sperm that are carried within a pollen tube to an ovule. One sperm fuses with the egg to form the zygote and the other fuses with the central cell to form the primary endosperm. The mechanisms that control male germline development and gene expression, and ensure that sperm properly fuse with female gametes are just beginning to be understood. Expression of the potent translation inhibitor, diphtheria toxin A subunit, from the Arabidopsis (Arabidopsis thaliana) HAP2(GCS1) promoter blocked sperm development before the final cell division, resulting in pollen tubes that carried a single sperm-like cell rather than two sperm. These pollen tubes targeted ovules and fertilized either the egg or the central cell, producing seeds with either endosperm or an embryo, but not both. Endosperm-only seeds significantly outnumbered embryo-only seeds, suggesting that single sperm-like cells preferentially fuse with the central cell. These experiments show that de novo translation is required for completion of sperm development, that the HAP2(GCS1) promoter is very tightly controlled, and that disruption of gene expression can result in male germ cells with a bias for gamete fusion.
1 This work was supported by the National Science Foundation (grant no. IOS–0644623 to M.J.) and the National Institutes of Health (training grant no. T32 GM 007601 to A.C.F.). The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Mark A. Johnson (mark_johnson_1{at}brown.edu). [W] The online version of this article contains Web-only data. [OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.109.144204 * Corresponding author; e-mail mark_johnson_1{at}brown.edu. Received July 2, 2009; accepted August 27, 2009; published September 4, 2009. Related articles in Plant Physiol.:
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