Köhler Claudia, Hennig Lars, Bouveret Romaric, Gheyselinck Jacqueline, Grossniklaus Ueli, Gruissem Wilhelm
Institute of Plant Biology and Zurich-Basel Plant Science Centre, University of Zurich, Zollikerstrasse 107, CH-8050 Zurich, Switzerland.
EMBO J. 2003 Sep 15;22(18):4804-14. doi: 10.1093/emboj/cdg444.
Seed development in angiosperms initiates after double fertilization, leading to the formation of a diploid embryo and a triploid endosperm. The active repression of precocious initiation of certain aspects of seed development in the absence of fertilization requires the Polycomb group proteins MEDEA (MEA), FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) and FERTILIZATION-INDEPENDENT SEED2. Here we show that the Arabidopsis WD-40 domain protein MSI1 is present together with MEA and FIE in a 600 kDa complex and interacts directly with FIE. Mutant plants heterozygous for msi1 show a seed abortion ratio of 50% with seeds aborting when the mutant allele is maternally inherited, irrespective of a paternal wild-type or mutant MSI1 allele. Further more, msi1 mutant gametophytes initiate endosperm development in the absence of fertilization at a high penetrance. After pollination, only the egg cell becomes fertilized, the central cell starts dividing prior to fertilization, resulting in the formation of seeds containing embryos surrounded by diploid endosperm. Our results establish that MSI1 has an essential function in the correct initiation and progression of seed development.
被子植物的种子发育在双受精后开始，导致形成二倍体胚胎和三倍体内胚乳。在未受精的情况下，对种子发育某些方面的早熟起始进行有效抑制需要多梳蛋白家族蛋白MEA（MEA）、非受精依赖型胚乳（FIE）和非受精依赖型种子2。在此我们表明，拟南芥WD-40结构域蛋白MSI1与MEA和FIE共同存在于一个600 kDa的复合物中，并直接与FIE相互作用。msi1杂合突变体植株的种子败育率为50%，当突变等位基因母系遗传时种子败育，无论父本是野生型还是突变型MSI1等位基因。此外，msi1突变配子体在未受精的情况下以高频率起始胚乳发育。授粉后，只有卵细胞受精，中央细胞在受精前开始分裂，导致形成含有被二倍体内胚乳包围的胚胎的种子。我们的结果表明，MSI1在种子发育的正确起始和进程中具有重要功能。
