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Double fertilization – caught in the act

2008; Elsevier BV; Volume: 13; Issue: 8 Linguagem: Inglês

10.1016/j.tplants.2008.05.011

1878-4372

Frédéric Berger, Yuki Hamamura, Mathieu Ingouff, Tetsuya Higashiyama,

Photosynthetic Processes and Mechanisms

In 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. In 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. the female gamete, which gives rise to the endosperm. Because the endosperm does not initiate a new life cycle, the central cell is not a true gamete. The central cell can be considered as the somatic part of the female gametophyte, which reinitiates its development after fertilization. the complex process leading to the production of the endosperm and the embryo. The major steps of double fertilization consist successively of (i) the attraction of the pollen tube toward the embryo sac containing the female gametes, (ii) the release of the two male gametes into the degenerated synergid, (iii) the migration of the male gametes by unknown mechanisms to the two female gametes, (iv) gamete recognition and fusion, (v) the fusion of the parental genetic material during karyogamy and (vi) reinitiation of the cell cycle and the transcription and translation that leads to the onset of the zygotic life. the female gamete, which produces the embryo. Because the product of the fertilized egg cell reinitiates the plant life cycle, the egg cell can be considered as the true female gamete. the female gametophyte, which contains four cell types three antipodals, the two synergids and the two female gametes, namely the central cell and the egg cell. the product of the fertilized central cell. The endosperm protects the embryo, controls the transfer of nutrients from the mother and, in some species, stores seed reserves. The role of the endosperm can be compared to that of the placenta in mammals. a structure composed of elaborate membrane folds and extracellular matrix protruding from the synergids in the micropyle. The filiform apparatus is probably the source of attractants for pollen tube guidance. the organism produced by the development of the spore. The gametophyte is haploid. It generally comprises a small number of cells with a size of the order of mm or cm, except in mosses, the gametophyte of which constitutes the major part of the life cycle. The germ line is defined in the gametophytic tissues. In many species there are male and female gametophytes. In flowering plants the gametophytic life is extremely reduced to a few cell divisions producing the embryo sac (female gametophyte) and the pollen (male gametophyte). maternal sporophytic tissues of the ovule surrounding the embryo sac. the fusion of the male and female nuclei. the area of the ovule where the pollen tube enters and abuts on the synergid filiform apparatus. the fusion of the plasma membrane of the male and female gamete. the two male gametes produced in the pollen. the diploid organism where meiosis takes place, producing the haploid spores. the two gametophytic cells on either the side of the egg cell that attract the pollen tube and control the release of the sperm cells.