Epigenetic regulation of developmental phase transition

多梳抑制复合物2（PRC 2）是基因表达和发育的重要调节因子。PRC 2蛋白在真菌、蠕虫、苍蝇、哺乳动物和许多植物物种中是保守的。在模式植物拟南芥中，PRC 2控制着胚乳的发育，胚乳是种子中为胚提供营养的组织。在单子叶植物中，如玉米，胚乳构成成熟种子的主要体积，并且它是可食用籽粒的主体。由于胚乳是种子的主要组成部分，因此对胚乳发育的了解对农业具有重要意义。在许多双子叶植物中，胚乳增殖是成熟种子大小的主要决定因素，如在拟南芥和相关作物植物油菜中所示。双子叶植物胚乳的增殖为随后的胚发育提供营养。该奖项的目的是更好地了解PRC 2如何调节胚乳形成。该项目增强了NSF的研究和教育任务。处于不同职业发展阶段的研究人员接受遗传学、分子生物学和生物化学领域的培训。学生和受训人员在职业发展、教学、沟通和人际交往技能以及专业发展方面得到指导。积极的推广活动促进科学素养和公众对科学的参与。在被子植物中，双受精导致二倍体胚和三倍体胚乳的形成。在许多双子叶植物中，种子发育涉及早期胚乳增殖以形成大胚囊，随后是胚生长以在成熟时取代大部分胚乳的第二阶段。一些对胚乳增殖至关重要的基因如MINI 3和IKU 2的表达在受精后被激活。授粉后4天（DAP），胚乳增殖基因被抑制，过渡到胚胎发育。PRC 2在发育阶段转换中起重要作用。在三种PRC 2复合体中，受精独立种子（FIS）-PRC 2通过组蛋白甲基化沉默胚乳增殖基因。PRC 2亚基中没有一个以序列特异性方式结合DNA，并且PRC 2如何被募集到特定基因组位点的知识是有限的。MEA是FIS-PRC 2复合物的组蛋白甲基转移酶，并积累4 DAP。与MEA积累平行，两个AGAMOUS样（AGL）MADS盒基因在4DAP被活跃地转录。两种AGL蛋白结合IKU 2启动子并与MEA相互作用。因此，MEA的动态积累调节胚乳增殖的持续时间，并且两个AGL是将MEA组蛋白编写者招募到IKU 2和其他潜在位点的阅读器。它们的共同作用促进了胚胎发育的阶段过渡。在这个项目中，动态MEA的积累与组蛋白修饰在IKU 2位点和招聘MEA的IKU 2和其他locisesexplored.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The polycomb repressive complex 2 (PRC2) is an important regulator of gene expression and development. PRC2 proteins are conserved in fungi, worm, fly, mammals and many plant species. In the model plant, Arabidopsis thaliana, PRC2 controls the development of the endosperm, the tissue in the seed that provides nutrients for the embryo. In monocots, like maize the endosperm constitutes the major volume of mature seeds and it the bulk of the edible kernel. Because the endosperm is a major constituent of seeds, an understanding of endosperm development has critical implications for agriculture. In many dicots, endosperm proliferation is the major determinant of mature seed size as has been shown in Arabidopsis thaliana and the related crop plant, canola. Endosperm proliferation in these dicots provides nutrient supplies for the subsequent embryo development. The aim of this award is to better understand how PRC2 regulates endosperm formation. This project augments the research and education missions of NSF. Researchers at different stages of their career development are trained in the fields of genetics, molecular biology and biochemistry. Students and trainees are mentored in the areas of career development, teaching, communication and interpersonal skills and professional development. Vigorous outreach activities foster scientific literacy and public engagement with science.In angiosperms, double fertilization leads to the formation of a diploid embryo and a triploid endosperm. In many dicots, seed development involves an early endosperm proliferation to form a large embryo sac followed by a second phase in which the embryo grows to replace most of the endosperm at maturity. The expression of a few genes critical for endosperm proliferation such as MINI3 and IKU2 is activated after fertilization. At 4 days after pollination (DAP), the endosperm proliferation genes are repressed for a transition to embryo development. PRC2s play important roles in developmental phase transition. Of the three PRC2 complexes, Fertilization Independent Seed (FIS)-PRC2 silences the endosperm proliferation genes through histone methylation. None of the PRC2 subunits bind DNA in a sequence-specific fashion, and the knowledge of how PRC2s are recruited to a particular genomic locus is limited. MEA is the histone methyltransferase of the FIS-PRC2 complex and accumulates 4 DAP. Parallel to MEA accumulation, two AGAMOUS-LIKE (AGL) MADS-box genes are actively transcribed 4 DAP. The two AGL proteins bind the IKU2 promoter and interact with MEA. Therefore, the dynamic accumulation of MEA regulates the duration of endosperm proliferation, and the two AGLs are the readers to recruit MEA histone writer to the IKU2 and other potential loci. Their co-action facilitates a phase transition to embryo development. In this project, the dynamic MEA accumulation in relation to histone modification at the IKU2 locus and the recruitment of MEA to the IKU2 and other loci is explored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.