The function and properties of RNA Polymerase IV in seed development

本研究探讨控制植物种子成功发育的机制。植物种子是所有农业的基础。种子是复杂的结构，由保护性的种皮、胚胎和有营养的胚乳组成。胚乳是生物圈中最重要的组织之一，它提供了人类消耗的三分之二的卡路里。虽然胚乳不传递任何遗传物质给下一代，但正常的胚乳发育对于形成有活力的种子和完成开花植物的生命周期至关重要。本项目主要研究植物特异性RNA聚合酶RNA Pol IV在胚乳发育和功能中的作用。该研究将增加对胚乳生物学的基本认识，并可能促进植物杂交的发展。该项目还为基因组学、植物生物学、表观遗传学、生物物理学和生物信息学领域的本科生、研究生和博士后提供跨学科、前沿的培训。教师也将参与拟议研究的各个方面，促进将科学发现和科学推理的兴奋转移到学生身上。胚乳有一个不寻常的基因构成——它是典型的三倍体，有两个母系遗传的基因组和一个父系遗传的基因组。RNA Pol IV调节胚乳中母本和父本基因拷贝之间的转录程序和表达平衡。已知RNA Pol IV是24个核苷酸小RNA的生物发生所必需的。通常，这些小rna来自转座元件和其他重复序列，并将DNA甲基化引导到匹配的基因组区域，这一过程称为rna定向DNA甲基化。DNA甲基化是一种影响转录的表观遗传标记。然而，在胚乳中，Pol IV活性、小rna、DNA甲基化和基因表达谱之间的关系基于目前对这一途径的理解是不可预测的。本研究的目的是确定RNA Pol IV如何、何时以及在何处影响拟南芥胚乳中母系和模式衍生基因组的基因转录和调节表达。目前认为，RNA Pol IV介导了胚乳中母系和父系基因组之间的冲突。本研究的具体目的是确定胚乳中RNA Pol IV活性如何调节基因表达，并确定RNA Pol IV对抗性母系和父系效应的遗传和分子基础。将采用多种遗传、基因组、生物物理和发育生物学方法来解决这些目标。这些研究活动将对受精前后调节亲本遗传冲突和促进种子活力的表观遗传过程提供实质性的新认识。该项目由生物科学理事会分子和细胞生物科学部的遗传机制项目和综合有机系统部的植物基因组研究项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research investigates the mechanisms that control successful plant seed development. Plant seeds are fundamental to of all agriculture. Seeds are complex structures, consisting of a protective seed coat, an embryo, and a nutritive endosperm. Endosperm is one of the most important tissues in the biosphere – it provides two-thirds of the calories consumed by humans. Although endosperm does not pass on any genetic material to the next generation, proper endosperm development is essential for the formation of viable seeds and the completion of the flowering plant life cycle. This project focuses on the contribution of a plant-specific RNA polymerase, RNA Pol IV, to endosperm development and function. The research will increase fundamental understanding of endosperm biology and may facilitate the development of plant hybrids. This project also provides interdisciplinary, cutting-edge training for undergraduates from groups under-represented in science, graduate students, and postdocs in genomics, plant biology, epigenetics, biophysics, and bioinformatics. Teachers will also participate in aspects of the proposed research, facilitating transfer of the excitement of scientific discovery and scientific reasoning to their students. Endosperm has an unusual genetic constitution – it is typically triploid, with two maternally-inherited and one paternally-inherited genomes. RNA Pol IV regulates transcriptional programs and the balance of expression between maternal and paternal gene copies in endosperm. It is known that RNA Pol IV is required for the biogenesis of 24 nucleotide small RNAs. Typically, these small RNAs arise from transposable elements and other repetitive sequences and direct DNA methylation to matching genomic regions in a process termed RNA-directed DNA methylation. DNA methylation is an epigenetic mark that can influence transcription. However, in endosperm the relationship between Pol IV activity, small RNAs, DNA methylation, and gene expression profiles is not predictable based on current understanding of this pathway. The goal of the proposed research is to determine how, when, and where RNA Pol IV acts to influence gene transcription and to regulate expression from maternally- and patternally-derived genomes in Arabidopsis thaliana endosperm. Current thought suggests that RNA Pol IV mediates conflict between maternal and paternal genomes in the endosperm. The specific objectives of the research are to determine how RNA Pol IV activity in endosperm regulates gene expression and to determine the genetic and molecular basis of antagonistic RNA Pol IV maternal and paternal effects. Diverse genetic, genomic, biophysical, and developmental biology approaches will be employed to address these aims. The research activities will provide substantial new understanding of the epigenetic processes that act before and after fertilization to mediate parental genetic conflicts and promote seed viability.This project is co-funded by the Genetic Mechanisms Program in the Division of Molecular and Cellular Biosciences and by the Plant Genome Research Program in the Division of Integrative Organismal Systems, both in the Directorate for Biological Sciences.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.