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  • 1
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    Control of female gamete formation by a small RNA pathway in Arabidopsis (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-03-09
    Description: In the ovules of most sexual flowering plants female gametogenesis is initiated from a single surviving gametic cell, the functional megaspore, formed after meiosis of the somatically derived megaspore mother cell (MMC). Because some mutants and certain sexual species exhibit more than one MMC, and many others are able to form gametes without meiosis (by apomixis), it has been suggested that somatic cells in the ovule are competent to respond to a local signal likely to have an important function in determination. Here we show that the Arabidopsis protein ARGONAUTE 9 (AGO9) controls female gamete formation by restricting the specification of gametophyte precursors in a dosage-dependent, non-cell-autonomous manner. Mutations in AGO9 lead to the differentiation of multiple gametic cells that are able to initiate gametogenesis. The AGO9 protein is not expressed in the gamete lineage; instead, it is expressed in cytoplasmic foci of somatic companion cells. Mutations in SUPPRESSOR OF GENE SILENCING 3 and RNA-DEPENDENT RNA POLYMERASE 6 exhibit an identical defect to ago9 mutants, indicating that the movement of small RNA (sRNAs) silencing out of somatic companion cells is necessary for controlling the specification of gametic cells. AGO9 preferentially interacts with 24-nucleotide sRNAs derived from transposable elements (TEs), and its activity is necessary to silence TEs in female gametes and their accessory cells. Our results show that AGO9-dependent sRNA silencing is crucial to specify cell fate in the Arabidopsis ovule, and that epigenetic reprogramming in companion cells is necessary for sRNA-dependent silencing in plant gametes.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613780/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613780/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Olmedo-Monfil, Vianey -- Duran-Figueroa, Noe -- Arteaga-Vazquez, Mario -- Demesa-Arevalo, Edgar -- Autran, Daphne -- Grimanelli, Daniel -- Slotkin, R Keith -- Martienssen, Robert A -- Vielle-Calzada, Jean-Philippe -- R01 GM067014/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2010 Mar 25;464(7288):628-32. doi: 10.1038/nature08828. Epub 2010 Mar 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Grupo de Desarrollo Reproductivo y Apomixis, Laboratorio Nacional de Genomica para la Biodiversidad y Departamento de Ingenieria Genetica de Plantas, Cinvestav Irapuato CP36500 Guanajuato, Mexico.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20208518" target="_blank"〉PubMed〈/a〉
    Keywords: Arabidopsis/genetics/growth & development/*metabolism ; Arabidopsis Proteins/genetics/*metabolism ; Argonaute Proteins ; DNA Transposable Elements/genetics ; Gametogenesis, Plant/*physiology ; Gene Expression Regulation, Plant ; Gene Silencing ; Meiosis ; Molecular Sequence Data ; Mutagenesis, Insertional/genetics ; Ovule/growth & development/*metabolism ; Phenotype ; RNA, Plant/*metabolism ; RNA-Binding Proteins/genetics/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
    Electronic Resource
    Electronic Resource
    Detection of the apomictic mode of reproduction in maize-Tripsacum hybrids using maize RFLP markers (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 1198-1203 
    Details
    ISSN: 1432-2242
    Keywords: Diplospory ; RFLP ; Bulk-segregant analysis ; Genome similarity ; Intergeneric hybrids ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polyploid plants in the genus Tripsacum, a wild relative of maize, reproduce through gametophytic apomixis of the diplosporous type, an asexual mode of reproduction through seed. Moving gene(s) responsible for the apomictic trait into crop plants would open new areas in plant breeding and agriculture. Efforts to transfer apomixis from Tripsacum into maize at CIMMYT resulted in numerou intergeneric F1 hybrids obtained from various Tripsacum species. A bulk-segregant analysis was carried out to identify molecular markers linked to diplospory in T. dactyloides. This was possible because of numerous genome similarities among related species in the Andropogoneae. On the basis of maize RFLP probes, three restriction fragments co-segregating with diplospory were identified in one maize-Tripsacum dactyloides F1 population that segregated 1∶1 for the mode of reproduction. The markers were also found to be linked in the maize RFLP map, on the distal end of the long arm of chromosome 6. These results support a simple inheritance of diplospory in Tripsacum. Manipulation of the mode of reproduction in maize-Tripsacum backcross generations, and implications for the transfer of apomixis into maize, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222943
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  • 3
    Electronic Resource
    Electronic Resource
    Dosage effects in the endosperm of diplosporous apomictic Tripsacum (Poaceae) (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 279-282 
    Details
    ISSN: 1432-2145
    Keywords: Key words Apomixis ; Tripsacum ; Endosperm ; Imprinting ; Flow cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Imprinting in the endosperm of angiosperms, a phenomena by which expression of alleles differs depending on whether they originate from the male or female parent, has been shown to explain most failure of interploidy or interspecific crosses in plants. Because of imprinting, seeds develop normally only if a specific dosage is represented in the endosperm, with the relative contributions of genomes in the ratio of two maternal doses to one paternal dose (2m:1p). In Tripsacum, a wild relative of maize, all polyploids reproduce through the diplosporous type of apomixis. Diplospory results from meiotic failure in megasporocytes that develop into eight-nucleate unreduced female gametophytes. The male gametophytes remain unaffected. Flow cytometry was used to determine ploidy levels in the endosperm of both apomictic and sexual Tripsacum accessions. In both cases, fertilization appeared to involve only one sperm nucleus. Therefore, endosperm of apomictic Tripsacum develops normally even though the ratio of genomic contributions deviates from the normal 2m:1p ratio. Ratios of 2:1, 4:1, 4:2, 8:1 and 8:2 were observed, depending on both the ploidy level of the parents and the mode of reproduction. Thus, specific dosage effects are seemingly not required for endosperm development in Tripsacum. These findings suggest that evolution of diplosporous apomixis might have been restricted to species with few or no imprinting requirements, and the findings have strong implications regarding the transfer of apomixis to sexually reproducing crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050098
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