The angiosperm seed is composed of three genetically distinct tissues: the diploid embryo that originates from the fertilized egg cell, the triploid endosperm that is produced from the fertilized central cell, and the maternal sporophytic integuments that develop into the seed coat1. At the onset of embryo development in Arabidopsis thaliana, the zygote divides asymmetrically, producing a small apical embryonic cell and a larger basal cell that connects the embryo to the maternal tissue2. The coordinated and synchronous development of the embryo and the surrounding integuments, and the alignment of their growth axes, suggest communication between maternal tissues and the embryo. In contrast to animals, however, where a network of maternal factors that direct embryo patterning have been identified3,4, only a few maternal mutations have been described to affect embryo development in plants5,6,7. Early embryo patterning in Arabidopsis requires accumulation of the phytohormone auxin in the apical cell by directed transport from the suspensor8,9,10. However, the origin of this auxin has remained obscure. Here we investigate the source of auxin for early embryogenesis and provide evidence that the mother plant coordinates seed development by supplying auxin to the early embryo from the integuments of the ovule. We show that auxin response increases in ovules after fertilization, due to upregulated auxin biosynthesis in the integuments, and this maternally produced auxin is required for correct embryo development.
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Early embryo development requires auxin production in the surrounding maternal integuments.
We thank E. Groot for assistance with statistical analyses and for critical reading of the manuscript. We thank J. Alonso for providing wei8-1, wei8-1 tar1-1, pDR5:GFP wei8-1, and pTAA1:GFP-TAA1 seeds, G. Jürgens for providing pDR5:nls-3xGFP and pDR5:nls-3xGFP wei8-1 tar1-1 seeds, T. Vernoux for p35S:DII-VENUS and p35S:mDII-VENUS seeds and plasmids, R. Offringa for pSDM7010 and pSDM7012, L. Lepiniec for pBAN-pBS-SK, C.-Y. Liao and D. Weijers for R2D2 seeds, and T. Friedrich for valuable suggestions. Seeds of wei8-3 and wei-11 seeds were obtained from the European Arabidopsis Stock Center (NASC). We acknowledge the CEITEC core facility CELLIM supported by the MEYS CR (LM2015062 Czech-BioImaging), and the CEITEC core facility Plant Sciences. H.S.R. was supported by the SoMoProII program co-financed by the South-Moravian Region and the European Union, by the Ministry of Education, Youth and Sports of the Czech Republic within CEITEC 2020 (LQ1601) and by the Masaryk University. C.P. was supported by the Kwanjeong Educational Foundation. C.L.G. was supported by the Deutscher Akademischer Austauschdienst. W.G. was a post-doctoral fellow of the Research Foundation Flanders. B.W. was supported by the ‘NITKA’ project under European Social Fund UDA-POKL.04.03.00-00-168/12, realized at the University of Silesia, Katowice, Poland. A.P and O.N. were supported by the Czech Foundation Agency (GA17-21581Y) and the Ministry of Education, Youth and Sports of the Czech Republic via the National Program for Sustainability (LO1204). J.C. is a post-doctoral fellow supported by a grant from the Deutsche Forschungsgemeinschaft (Dr334/10) to T.D. This work was further supported by the European Research Council (FP7/2007-2013 / ERC-grant agreement no. 282300 to J.F.), and the Czech Science Foundation GACR (GA13-40637S) to J.F.; and by the Deutsche Forschungsgemeinschaft (La606/6, La606/13, La606/17 and ERA-CAPS program), and the EU 7th framework program (ITN SIREN) to T.L. This material reflects only the author’s views and the European Union is not liable for any use that may be made of the information contained therein.
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Clearance of maternal barriers by paternal miR159 to initiate endosperm nuclear division in Arabidopsis
Nature Communications (2018)