Department of Biology and Zurich-Basel Plant Science Center, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland.
Development. 2012 Jun;139(11):2031-9. doi: 10.1242/dev.077057. Epub 2012 Apr 25.
The endosperm is a terminal seed tissue that is destined to support embryo development. In most angiosperms, the endosperm develops initially as a syncytium to facilitate rapid seed growth. The transition from the syncytial to the cellularized state occurs at a defined time point during seed development. Manipulating the timing of endosperm cellularization through interploidy crosses negatively impacts on embryo growth, suggesting that endosperm cellularization is a critical step during seed development. In this study, we show that failure of endosperm cellularization in fertilization independent seed 2 (fis2) and endosperm defective 1 (ede1) Arabidopsis mutants correlates with impaired embryo development. Restoration of endosperm cellularization in fis2 seeds by reducing expression of the MADS-box gene AGAMOUS-LIKE 62 (AGL62) promotes embryo development, strongly supporting an essential role of endosperm cellularization for viable seed formation. Endosperm cellularization failure in fis2 seeds correlates with increased hexose levels, suggesting that arrest of embryo development is a consequence of failed nutrient translocation to the developing embryo. Finally, we demonstrate that AGL62 is a direct target gene of FIS Polycomb group repressive complex 2 (PRC2), establishing the molecular basis for FIS PRC2-mediated endosperm cellularization.
胚乳是一种终端种子组织，注定要支持胚胎发育。在大多数被子植物中，胚乳最初发育为合胞体，以促进种子的快速生长。从合胞体到细胞化状态的转变发生在种子发育的特定时间点。通过异倍体杂交人为改变胚乳细胞化的时间会对胚胎生长产生负面影响，这表明胚乳细胞化是种子发育过程中的一个关键步骤。在这项研究中，我们表明，在受精不依赖种子 2 (fis2) 和胚乳缺陷 1 (ede1) 拟南芥突变体中，胚乳细胞化的失败与胚胎发育受损相关。通过降低 MADS-box 基因 AGAMOUS-LIKE 62 (AGL62) 的表达，在 fis2 种子中恢复胚乳细胞化促进了胚胎发育，强烈支持胚乳细胞化对于形成有活力的种子是必不可少的。fis2 种子中胚乳细胞化的失败与己糖水平的升高有关，这表明胚胎发育的停滞是由于营养物质向发育中的胚胎转运失败所致。最后，我们证明 AGL62 是 FIS 多梳抑制复合物 2 (PRC2) 的直接靶基因，为 FIS PRC2 介导的胚乳细胞化建立了分子基础。
