Auxin-Dependent Patterning and Gamete Specification in the Arabidopsis Female Gametophyte

Department of Plant Biology, University of California, Davis, CA 95616, USA.
Science (Impact Factor: 33.61). 07/2009; 324(5935):1684-9. DOI: 10.1126/science.1167324
Source: PubMed


The female reproductive unit of flowering plants, the haploid female gametophyte, is highly reduced relative to other land plants. We show that patterning of the Arabidopsis female gametophyte depends on an asymmetric distribution of the hormone auxin during its syncitial development. Furthermore, this auxin gradient is correlated with location-specific auxin biosynthesis, rather than auxin efflux that directs patterning in the diploid sporophytic tissues comprising the rest of the plant. Manipulation of auxin responses or synthesis induces switching of gametic and nongametic cell identities and specialized nonreproductive cells to exhibit attributes presumptively lost during angiosperm evolution. These findings may account for the unique egg cell specification characteristic of angiosperms and the formation of seeds with single diploid embryos while containing endosperm that can have variable numbers of parental haploid genomes.

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Available from: Monica Alandete-Saez, Nov 18, 2014
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    • "There have been major advances in our understanding of the events regulating germline development and gamete specification in angiosperms (Berger and Twell, 2011; Twell, 2011). The cellularization and differentiation of cells in the embryo sac appear to be transcriptionally regulated (Rabiger and Drews, 2013), and mechanisms involving RNA splicing and auxin and peptide signaling specify female gametic cells (Gross-Hardt et al., 2007; Pagnussat et al., 2009; Lieber et al., 2011; Lituiev et al., 2013). For male germline development, a regulatory framework for cell cycle progression and gamete specification has been established (Brownfield and Twell, 2009; Borg and Twell, 2010; Twell, 2011). "
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    ABSTRACT: The production of the sperm cells in angiosperms requires coordination of cell division and cell differentiation. In Arabidopsis thaliana, the germline-specific MYB protein DUO1 integrates these processes, but the regulatory hierarchy in which DUO1 functions is unknown. Here, we identify an essential role for two germline-specific DUO1 target genes, DAZ1 and DAZ2, which encode EAR motif-containing C2H2-type zinc finger proteins. We show that DAZ1/DAZ2 are required for germ cell division and for the proper accumulation of mitotic cyclins. Importantly, DAZ1/DAZ2 are sufficient to promote G2- to M-phase transition and germ cell division in the absence of DUO1. DAZ1/DAZ2 are also required for DUO1-dependent cell differentiation and are essential for gamete fusion at fertilization. We demonstrate that the two EAR motifs in DAZ1/DAZ2 mediate their function in the male germline and are required for transcriptional repression and for physical interaction with the corepressor TOPLESS. Our findings uncover an essential module in a regulatory hierarchy that drives mitotic transition in male germ cells and implicates gene repression pathways in sperm cell formation and fertility.
    The Plant Cell 05/2014; 26(5):2098-113. DOI:10.1105/tpc.114.124743 · 9.34 Impact Factor
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    • "In addition, it was proposed that adaxial–abaxial polarity mechanisms were required for integument formation [13,14]. The auxin concentration gradient was found to determine cell fates in the embryo sac [15]. Two genes (AGO5 and AGO9) were shown to control female gamete formation and megagametogenesis by two independent small RNA pathways [16,17]. "
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    BMC Genomics 01/2014; 15(1):61. DOI:10.1186/1471-2164-15-61 · 3.99 Impact Factor
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    • "Evidence regarding the role of auxin in the cell fate specification of embryo sac development has recently been obtained. In Arabidopsis, two YUCCA (YUC) genes encoding proteins that are crucial for local auxin biosynthesis were shown to be expressed in the ovule, which is consistent with the role of auxin as a cell fate determinant (Pagnussat et al. 2009). Owing to the high concentrations of auxin detected in the distal tip of the nucellus at early stages of ovule development (Pagnussat et al. 2009) and because SPOROCYTELESS/NOZZLE (SPL) was demonstrated to repress the expression of YUCCA genes (Li et al. 2008), it is likely that auxin plays a key role in the cell specification machinery that regulates differentiation of the MMC and/or maintains the undifferentiated state of nucellar cells once the MMC is formed. "
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