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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    • "In what is now a familiar theme, this gradient of cytokinin mirrors an auxin gradient present in the sporophytic tissue early in female gametophyte development (Pagnussat et al., 2009) that is likely formed through the action of PIN1 (Ceccato et al., 2013). This auxin gradient was suggested to define cell-type specification in the female gametophyte (Pagnussat et al., 2009), though Lituiev et al. (2013) suggested, on theoretical grounds and an analysis of a degron-based auxin sensor, that there was no auxin gradient in the female gametophyte itself, though they did observe a gradient in the surrounding sporophytic tissue. This suggests that in the sporophytic tissues, there are opposing auxin and cytokinin gradients that play complementary roles during early stages of female gametophyte development, including the specification of the functional megaspore cell from the four products arising from meiosis of the megaspore mother cell (C.-Y. "
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    ABSTRACT: The phytohormones auxin and cytokinin interact to regulate many plant growth and developmental processes. Elements involved in the biosynthesis, inactivation, transport, perception, and signaling of these hormones have been elucidated, revealing the variety of mechanisms by which signal output from these pathways can be regulated. Recent studies shed light on how these hormones interact with each other to promote and maintain plant growth and development. In this review, we focus on the interaction of auxin and cytokinin in several developmental contexts, including its role in regulating apical meristems, the patterning of the root, the development of the gynoecium and female gametophyte, and organogenesis and phyllotaxy in the shoot. © 2015 American Society of Plant Biologists. All rights reserved.
    The Plant Cell 01/2015; 27(1). DOI:10.1105/tpc.114.133595 · 9.34 Impact Factor
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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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    ABSTRACT: The gynoecium is one of the most complex organs of angiosperms specialized for seed production and dispersal, but only several genes important for ovule or embryo sac development were identified by using female sterile mutants. The female sterility in oilseed rape (Brassica napus) was before found to be related with one alien chromosome from another crucifer Orychophragmus violaceus. Herein, the developmental anatomy and comparative transcript profiling (RNA-seq) for the female sterility were performed to reveal the genes and possible metabolic pathways behind the formation of the damaged gynoecium. The ovules in the female sterile Brassica napus with two copies of the alien chromosomes (S1) initiated only one short integument primordium which underwent no further development and the female gametophyte development was blocked after the tetrad stage but before megagametogenesis initiation. Using Brassica_ 95k_ unigene as the reference genome, a total of 28,065 and 27,653 unigenes were identified to be transcribed in S1 and donor B. napus (H3), respectively. Further comparison of the transcript abundance between S1 and H3 revealed that 4540 unigenes showed more than two fold expression differences. Gene ontology and pathway enrichment analysis of the Differentially Expressed Genes (DEGs) showed that a number of important genes and metabolism pathways were involved in the development of gynoecium, embryo sac, ovule, integuments as well as the interactions between pollen and pistil. DEGs for the ovule development were detected to function in the metabolism pathways regulating brassinosteroid (BR) biosynthesis, adaxial/abaxial axis specification, auxin transport and signaling. A model was proposed to show the possible roles and interactions of these pathways for the sterile gynoecium development. The results provided new information for the molecular mechanisms behind the gynoecium development at early stage in B. napus.
    BMC Genomics 01/2014; 15(1):61. DOI:10.1186/1471-2164-15-61 · 3.99 Impact Factor
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