Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center of Plant Biology, Uppsala, Sweden.
PLoS Genet. 2013;9(1):e1003163. doi: 10.1371/journal.pgen.1003163. Epub 2013 Jan 10.
Seed development in flowering plants is initiated after a double fertilization event with two sperm cells fertilizing two female gametes, the egg cell and the central cell, leading to the formation of embryo and endosperm, respectively. In most species the endosperm is a polyploid tissue inheriting two maternal genomes and one paternal genome. As a consequence of this particular genomic configuration the endosperm is a dosage sensitive tissue, and changes in the ratio of maternal to paternal contributions strongly impact on endosperm development. The fertilization independent seed (FIS) Polycomb Repressive Complex 2 (PRC2) is essential for endosperm development; however, the underlying forces that led to the evolution of the FIS-PRC2 remained unknown. Here, we show that the functional requirement of the FIS-PRC2 can be bypassed by increasing the ratio of maternal to paternal genomes in the endosperm, suggesting that the main functional requirement of the FIS-PRC2 is to balance parental genome contributions and to reduce genetic conflict. We furthermore reveal that the AGAMOUS LIKE (AGL) gene AGL62 acts as a dosage-sensitive seed size regulator and that reduced expression of AGL62 might be responsible for reduced size of seeds with increased maternal genome dosage.
植物的种子发育是在双受精事件之后开始的，两个精子细胞分别受精于卵细胞和中央细胞，分别形成胚胎和胚乳。在大多数物种中，胚乳是一种多倍体组织，继承了两个母本基因组和一个父本基因组。由于这种特殊的基因组结构，胚乳是一个剂量敏感的组织，母本和父本贡献的比例变化强烈影响胚乳的发育。受精独立的种子（FIS）多梳抑制复合物 2（PRC2）对于胚乳发育是必不可少的；然而，导致 FIS-PRC2 进化的潜在力量仍然未知。在这里，我们表明，通过增加胚乳中母本到父本基因组的比例，可以绕过 FIS-PRC2 的功能需求，这表明 FIS-PRC2 的主要功能需求是平衡亲本基因组的贡献，并减少遗传冲突。我们还揭示了 AGAMOUS LIKE（AGL）基因 AGL62 作为一个剂量敏感的种子大小调节因子，并且降低 AGL62 的表达可能是导致增加母本基因组剂量的种子变小的原因。
