Expressing the Diphtheria Toxin A Subunit from the HAP2(GCS1) Promoter Blocks Sperm Maturation and Produces Single Sperm-Like Cells Capable of Fertilization

Department of Molecular Biology, Brown University, Providence, Rhode Island 02912, USA.
Plant physiology (Impact Factor: 7.39). 10/2009; 151(3):1390-400. DOI: 10.1104/pp.109.144204
Source: PubMed

ABSTRACT 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Sexual reproduction of flowering plants is distinguished by double fertilization-the two sperm cells delivered by a pollen tube fuse with the two gametic cells of the female gametophyte, the egg and the central cell-inside the ovule to give rise to the embryo and the nutritive endosperm, respectively [1]. The pollen tube is attracted by nongametic synergid cells, and how these two cells of the female gametophyte are specified is currently unclear. Here, we show that ALTERED MERISTEM PROGRAM 1 (AMP1), encoding a protein associated with the endoplasmic reticulum [2], is required for synergid cell fate during Arabidopsis female gametophyte development. Loss of AMP1 function leads to supernumerary egg cells at the expense of synergids, enabling the generation of dizygotic twins. However, if twin embryos are formed, endosperm formation is prevented, eventually resulting in ovule abortion. The latter can be overcome by the delivery of supernumerary sperm cells in tetraspore (tes) pollen [3], enabling the formation of twin plants. Thus, both primary and supernumerary egg cells are fully functional in amp1 mutant plants. Sporophytic AMP1 expression is sufficient to prevent cell-fate change of synergids, indicating that one or more AMP1-dependent mobile signals from outside the female gametophyte can contribute to its patterning, in addition to the previously reported lateral inhibition between gametophytic cells [4-6]. Our results provide insight into the mechanism of synergid fate specification and emphasize the importance of specifying only one egg cell within the female gametophyte to ensure central-cell fertilization by the second sperm cell. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Current Biology 12/2014; 25(2). DOI:10.1016/j.cub.2014.11.021 · 9.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pollen, regarded as the gold dust carrying the male germ line of flowering plants, is generated in the male reproductive organ called stamen. During the last few years, molecular biology and genetics have been integrated to enhance our knowledge regarding the structural and functional aspects of anther and pollen development. The promoters of several anther-/pollen-specific genes have been characterized to help understand the development of anther that involves the expression of a large number of genes temporally as well as spatially. The cis-acting regulatory elements of promoters necessary for interaction with transcription factors and their activity have been delineated. Many transcription factor genes having distinct anther-specific expression pattern have been identified with the help of transcriptome studies in Oryza sativa as well as Arabidopsis thaliana. The nature of complex interactions between genes and regulatory hierarchy involving developmental signal cascades have been investigated to design a working model for anther development. The immediate challenge ahead is to isolate and functionally characterize missing links and terminal ends of regulatory components for enhancing our knowledge about the male gametophyte development. The information generated on this aspect would help design suitable strategies to develop traits such as male sterility in crop plants.
    Critical Reviews in Plant Sciences 09/2012; 31(5). DOI:10.1080/07352689.2012.664986 · 5.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: α-kleisins are core components of meiotic and mitotic cohesin complexes. Arabidopsis contains genes encoding four α-kleisins. SYN1, a REC8 ortholog, is essential for meiosis, while SYN2 and SYN4 appear to be SCC1 orthologs and function in mitosis. SYN3is enriched in the nucleolus of meiotic and mitotic cells and is essential for megagametogenesis. It was recently shown that expression of SYN3 RNAi constructs in buds cause changes in meiotic gene expression that result in meiotic alterations. In this report we show that expression of SYN3 from the 35S promoter with either a c-terminal Myc or FAST tag causes a reduction in SYN1 mRNA levels that results in alterations in sister chromatid cohesion, homologous chromosome synapsis and synaptonemal complex formation during both male and female meiosis.
    Journal of Genetics and Genomics 01/2013; DOI:10.1016/j.jgg.2013.11.006 · 2.92 Impact Factor


1 Download
Available from