Changing fates: rewiring gene expression in barley androgenesis

改变命运：重新连接大麦雄激素发生中的基因表达

• 批准号: RGPIN-2017-04762
• 负责人: Belzile, François
• 金额: $ 2.33万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711211
• 关键词: Changing; fates; rewiring; gene; expression

In barley, it is possible to obtain plants derived from a single immature microspore, the type of cell that usually leads to the production of pollen grains. This is termed androgenesis, i.e. the process of obtaining a plant carrying only the genetic material (chromosomes) of the male parent. Indeed, microspores only carry a single copy of each barley chromosome, contrary to the pair normally carried in the barley plant. If this situation remains unchanged throughout the entire development of the plant derived from this microspore, it will result in these plants being sterile. Fortunately, a majority of the plants regenerated from immature microspores via androgenesis will undergo a spontaneous doubling of their chromosomes, thus restoring fertility. Such plants are termed "doubled haploid" and are highly valuable tools in both genetic analysis and breeding. Indeed, androgenesis is often used in plant breeding to expedite the development of new and improved varieties. Although widely used, we have a rather limited understanding of how it is that a cell, normally destined to form a pollen grain, can undergo a complete shift in fate and start dividing in a highly organized fashion to produce an embryo and eventually a new plant. We hypothesize that this dramatic change in fate is due to a profound and rapid reprogramming of the genes that are expressed in the microspore. One can imagine that two types of processes need to occur: 1) the products of the genes needed to continue on the path towards pollen need to be destroyed (the slate has to be cleaned); and 2) new genes need to be expressed in order for the microspore to engage on the path to producing an embryo (a new set of instructions has to be given). We thus expect that major changes must occur to the list of expressed genes and their products found in the cell. We propose to investigate these changes (contrasting gene expression in both the path leading to pollen and the path leading to embryos) through a technique called RNA-Seq, a method that allow the extensive cataloguing of all the genes that are expressed in a cell. To further explore how the necessary turnover occurs in the cell, we propose to investigate the population of small RNAs found in developing microspores. Such small RNAs have been shown to play important roles in development, both in plants and animals. Some specific types of small RNAs are known to target the destruction of some gene products. If this is the case when the microspore is undergoing its shift towards androgenesis, we expect to find small RNAs capable of directing the elimination of gene products normally needed to "build" a grain of pollen. Once a microspore has been thus deprogrammed, it can be reprogrammed to develop into an embryo by expressing a new suite of genes. The results of this work will both enhance our basic knowledge of how plant cells can be reprogrammed and provide useful tools for optimizing androgenesis in barley.

在大麦中，可以获得源自单个未成熟小孢子的植物，这种细胞类型通常导致花粉粒的产生。这称为雄激素发生，即获得仅携带父本遗传物质（染色体）的植物的过程。事实上，小孢子只携带每个大麦染色体的单个拷贝，这与大麦植株中通常携带的一对相反。如果这种情况在源自该小孢子的植物的整个发育过程中保持不变，则会导致这些植物不育。幸运的是，大多数由未成熟小孢子通过雄激素发生再生的植物将经历染色体自发加倍，从而恢复生育能力。此类植物被称为“双单倍体”，是遗传分析和育种中非常有价值的工具。事实上，雄激素发生经常用于植物育种，以加速新品种和改良品种的开发。 虽然被广泛使用，但我们对通常注定要形成花粉粒的细胞如何经历命运的彻底转变并开始以高度组织化的方式分裂以产生胚胎并最终产生新植物的了解相当有限。我们假设命运的这种巨大变化是由于小孢子中表达的基因发生了深刻而快速的重编程。人们可以想象，需要发生两种类型的过程：1）需要销毁继续形成花粉的基因产物（必须清理石板）； 2) 需要表达新的基因，以便小孢子能够走上产生胚胎的道路（必须给出一套新的指令）。因此，我们预计细胞中发现的表达基因及其产物的列表必须发生重大变化。我们建议通过一种称为 RNA-Seq 的技术来研究这些变化（对比导致花粉的路径和导致胚胎的路径中的基因表达），这种方法允许对细胞中表达的所有基因进行广泛的编目。 为了进一步探索细胞中必要的周转是如何发生的，我们建议研究发育中小孢子中发现的小 RNA 群体。此类小 RNA 已被证明在植物和动物的发育中发挥着重要作用。已知某些特定类型的小 RNA 可靶向破坏某些基因产物。如果是这种情况，当小孢子正在向雄性发生转变时，我们期望找到能够指导消除通常“构建”花粉粒所需的基因产物的小RNA。一旦小孢子被解编程，它就可以通过表达一套新的基因重新编程以发育成胚胎。 这项工作的结果将增强我们对植物细胞如何重新编程的基础知识，并为优化大麦雄激素发生提供有用的工具。