Patterning of the Female Gametophyte in Arabidopsis

摘要开花植物的繁殖依赖于配子体的产生，配子体是植物生命周期的单倍体阶段，由花的生殖器官产生，含有亲本植物染色体集的一半。种子的形成需要称为胚囊的雌性配子体与含有精子细胞的花粉粒的雄性配子体受精。成熟的雌性配子体或胚囊仅由四种细胞类型组成，其中包括两个配子。卵细胞和中央细胞，由一个精确的发育程序的执行而产生。本项目将利用模式植物拟南芥研究胚囊发育模式形成的分子机制。在拟南芥中发现了一种不寻常的突变，eostre，即胚囊中有一个额外的卵细胞代替另一个称为协同细胞的细胞。eostre突变体的特征表明，BELL和II类Knox同源结构域家族的转录调节因子，以及OVATE家族的相互作用蛋白，调节胚囊内的细胞规格。鉴定这些基因家族中在雌性配子体发育中起作用的特定成员及其在胚胎囊细胞身份规范中的可能作用。此外，新的实验证据表明，植物激素生长素的信号传导在胚囊中建立细胞身份。生长素在胚囊细胞规范中的功能将通过基因突变和RNA沉默以及跟踪生长素浓度和运输的细胞标记进一步研究。这些研究将有助于了解雌性配子体的发育机制和功能。由于胚囊在种子形成中起着核心作用，从这些研究中获得的知识在作物植物的繁殖控制和增加种子产量方面具有重要的潜在应用价值。该项目还将通过为生命科学和生物技术专业人员提供宝贵的研究经验和培训，为博士后提供植物生殖遗传学和分子生物学方面的全面培训，并为本科生（包括来自代表性不足群体的学生）提供研究机会。

PI: Venkatesan SundaresanProposal Number: IOS-0745167Title: Patterning of the female gametophyte in ArabidopsisAbstractThe reproduction of flowering plants relies on the production of gametophytes, the haploid phase of the plant life cycle generated by the reproductive organs of the flower, containing half the chromosome set of the parent plant. Seed formation requires that female gametophytes called embryo sacs, be fertilized by male gametophytes which are pollen grains containing sperm cells. The mature female gametophyte or embryo sac consists of only four cell types, including two gametes ? the egg cell and central cell, resulting from the execution of a precise developmental program. This project will use the model plant Arabidopsis to study the molecular mechanisms that govern the formation of developmental pattern in the embyo sac. An unusual mutation, eostre, in which the embryo sac has an additional egg cell in place of another cell called a synergid cell, has been identified in Arabidopsis. Characterization of the eostre mutant shows that transcriptional regulators of the BELL and class II Knox homeodomain families, and interacting proteins of the OVATE family, regulate cell specification in the embryo sac. Identification of specific members of these gene families that function in female gametophyte development and their possible roles in specification of cell identities in the embryo sac will be undertaken. In addition, new experimental evidence indicates that signaling by the plant hormone auxin establishes cell identity in the embryo sac. The function of auxin in cell specification in the embryo sac will be further investigated through approaches employing genetic mutants and RNA silencing as well as cellular markers that track auxin concentrations and transport. The proposed studies will provide an understanding of the mechanisms underlying development and function of the female gametophyte. As the embryo sac plays a central role in seed formation, the knowledge gained from these studies has important potential applications towards the control of reproduction and increased seed production in crop plants. The project will also provide comprehensive training in genetics and molecular biology of plant reproduction for postdoctoral fellows, and research opportunities for undergraduate students, including students from underrepresented groups, by providing valuable research experience and training for the life sciences and biotechnology professions.