核转运蛋白IMF调控胚珠发育的分子机理研究

Ovules are progenitors of seeds. Ovular development is therefore critical for plant reproduction and seed yield. Because the limited number of ovules an individual plant produces is much fewer than that of pollen grains, ovule development is thus a limiting factor for crop yield. In addition to its agronomical impact, ovules are multi-cellular tissues not only with a complex tissue polarity but also contain cells from two generations: the sporophytic inner and outer integument cells as well as the gametophytic embryo sac. Therefore, to investigate the molecular mechanism underlying ovular development is not only critical for agricultural productivity but also useful to understand basic biological questions, such as mechanisms of tissue polarity establishment and inter-cellular communication. .Studies in the past decade uncovered many transcription factors (TFs) controlling ovule development. However, regulatory components of these TFs are obscure. ..Previously, we characterized an Arabidopsis gene, IMPORTIN-FOR-FERTILIZATION (IMF). Functional loss of IMF resulted in defective ovule development. Specifically, imf mutants could not form regular outer integuments, contain defective embryo sacs and are partially female sterile. .This project thus aims at understanding the signaling pathway and related components in IMF-mediated ovule development. Specifically, we propose to 1) characterize the ovular developmental defects of imf in details; 2) identify key transcription factors whose nucleo-cytoplasmic shuttling depends on IMF by using protein interaction assays; 3) identify interacting proteins of these TFs and dissect downstream events mediated by IMF-TFs. By these approaches, we hope to establish the IMF-TF signaling pathway controlling ovule development and provide novel insights into molecular mechanism underlying ovule development.

胚珠是种子的前体，其发育正常与否直接关系到植物个体的繁衍及产量。植物个体产生的胚珠数量有限，胚珠发育因而成为产量形成的关键因素。此外，胚珠具有复杂的组织极性，包含孢子体及配子体两个世代的细胞。因此，研究胚珠发育的分子调控机制，对于了解种子的形成和发育至关重要，而且有助于回答细胞间信号交流机制等基础生物学问题。已有研究揭示了控制胚珠发育的部分转录因子。然而，调控这些转录因子发挥功能的元件尚未被发现。申请人目前鉴定了拟南芥核转运蛋白IMF，其突变体胚珠发育异常，表现在珠被细胞极性生长缺陷、胚囊不能正常形成，造成雌性部分不育。本项目拟对imf进行深入的表型分析，明确其在胚珠发育中的作用；通过蛋白互作及候选基因筛选等方法，发掘鉴定依赖于IMF进行核转运的转录因子；结合转录组测序，对该转录因子及下游途径进行深入解析，从而阐明IMF介导转录因子入核、调控胚珠发育的信号途径，为深入解析胚珠发育的分子机制

胚珠是种子的前体，其正常发育对完成双受精过程至关重要。前期的研究结果表明多种转录因子参与胚珠发育过程。然而，这些转录因子的上游调控因子尚未被揭示。课题组在本研究中综合运用细胞生物学、生物化学、分子生物学，以及遗传学等手段，发现核专员蛋白IMB4功能缺失导致胚珠珠被发育异常，进而影响胚囊发育，最终导致部分雌配子体败育。进一步发现IMB4与转录激活因子GIFs互作，促进GIFs在细胞核内的富集，从而介导胚珠发育。另一方面，与IMB4同源的拟南芥核转运蛋白KETCH1参与胚囊发育。KETCH1突变造成雌配子体停滞在第一次有丝分裂期。研究组发现KETCH1与多种核糖体蛋白互作，从而防止这些核糖体蛋白在核内受到26S蛋白酶体途径降解，保证其在核内丰度。研究结果为揭示胚珠发育过程中雌配子体与珠被细胞协同，以及雌配子体有丝分裂进程的调控机制提供了重要参考信息。在本项目的支持下，课题组4年间发表标注SCI论文8篇，包括Plant Cell, Mol Plant, Plant Physiol, PLOS Genet等。其中4篇SCI论文以本项目为第一标注基金。