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Understanding the origin of parthenogenesis

了解孤雌生殖的起源

基本信息

批准号：
10874028
负责人：
Sen Xu
金额：
$ 37.27万
依托单位：
UNIVERSITY OF MISSOURI-COLUMBIA
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-07-01 至 2024-06-30
项目状态：
已结题

项目摘要

Project Summary Parthenogenesis (i.e., reproduction without mating) has evolved from sexual reproduction in nearly all major eukaryotic groups. In parthenogenesis, chromosomally unreduced (e.g., diploid) gametes result from modified forms of meiosis. Understanding the genetic mechanisms underlying the modification of meiosis in parthenogenetic lineages is of significant public health interest because meiosis is central to sexual reproduction. Using parthenogenesis to understand the genetic regulation of meiosis is also a highly innovative approach, with its natural history perspective most likely yielding novel knowledge about meiosis. Using a combination of evolutionary and functional genomic approaches, this project examines the genetic bases of cyclical and obligate parthenogenesis in the freshwater microcrustacean Daphnia, which represents an excellent tractable experimental system with well-understood biology and many genomic tools. Daphnia is well known for its cyclical parthenogenesis (CP) life cycle, i.e., propagating asexually under favorable environmental conditions and switching to sexual reproduction in response to stressful environment. Interestingly, some populations of the species D. pulex (backcrosses of two parental CP species D. pulex and D. pulicaria) reproduce by obligate parthenogenesis (OP) because they lost the capability to engage in sex. This project has two long-term goals. First, considering that a single Daphnia genome can encode the genetic machinery for both reproductive strategies, it is hypothesized that environment-mediated gene expression changes, especially the neofunctionalization of duplicated meiosis genes (e.g. Cdc20), play a role in the origin of CP. To test this, ovary- specific gene expression changes between parthenogenesis and meiosis in CP D. pulex and D. pulicaria will be examined to produce a high quality set of candidate genes. To determine the functional role of these candidates in CP (e.g., master regulator genes), we will perform RNAi knockdown of each candidate in CP isolates and examine the associated phenotypic effects using animal reproduction assay and cytological examination of developing oocytes. Second, concerning the origin of OP, we hypothesize that the genetic incompatibility between the two ecologically divergent species CP D. pulex and D. pulicaria is a key factor. For the previously identified candidate genes for OP, we will test (1) whether they experience differential gene expression in OP isolates compared to CP isolates and (2) whether their expression is mis-regulated (i.e., genetic incompatibility). The former will be achieved by ovary-specific RNA-seq in OP and CP clones at different reproductive stages, whereas the latter will be based on allele-specific RNA-seq analysis of the parental species and OP isolates. For the candidate genes showing differential expression and mis-regulation, RNAi knockdown and phenotype screening will be performed to verify their functional role in OP, whereas CRISPR/Cas9 editing will be used to identify the causal SNPs for each gene. Lastly, we will re-create OP animals by introducing OP-causal SNPs to CP Daphnia pulex using CRISPR/Cas9 editing.

项目概要几乎所有主要的单性生殖（即不交配的繁殖）都是从有性生殖进化而来的。真核生物群体。在孤雌生殖中，染色体未减少的配子（例如二倍体）是由修饰的配子产生的减数分裂的形式。了解减数分裂修饰背后的遗传机制孤雌生殖谱系具有重要的公共卫生意义，因为减数分裂是有性生殖的核心。利用孤雌生殖来了解减数分裂的遗传调控也是一种高度创新的方法，它的自然历史观点很可能产生有关减数分裂的新知识。使用组合进化和功能基因组方法，该项目研究了周期性和专性基因组的遗传基础淡水微型甲壳动物水蚤的孤雌生殖，代表了一种极易驯化的水蚤具有深入了解的生物学和许多基因组工具的实验系统。水蚤以其周期性而闻名孤雌生殖（CP）生命周期，即在有利的环境条件下无性繁殖为了应对压力环境而转向有性生殖。有趣的是，一些人群 D. pulex 物种（两个亲本 CP 物种 D. pulex 和 D. pulicaria 的回交）通过专性繁殖孤雌生殖（OP），因为它们失去了进行性行为的能力。该项目有两个长期目标。首先，考虑到单个水蚤基因组可以编码生殖和繁殖的遗传机制。策略，假设环境介导的基因表达发生变化，尤其是重复减数分裂基因（例如 Cdc20）的新功能化在 CP 的起源中发挥作用。为了测试这一点，卵巢- CP D. pulex 和 D. pulicaria 的孤雌生殖和减数分裂之间的特定基因表达变化将是进行检查以产生一组高质量的候选基因。确定这些候选人的职能角色在 CP（例如主调控基因）中，我们将对 CP 分离株中的每个候选基因进行 RNAi 敲低，使用动物繁殖测定和细胞学检查检查相关的表型效应正在发育的卵母细胞。其次，关于 OP 的起源，我们假设遗传不相容性 CP D. pulex 和 D. pulicaria 这两个生态上不同的物种之间的差异是一个关键因素。对于之前的确定了 OP 的候选基因，我们将测试（1）它们是否在 OP 中经历差异基因表达分离株与 CP 分离株相比，以及 (2) 它们的表达是否被错误调节（即遗传不相容）。前者将通过不同生殖阶段的 OP 和 CP 克隆中的卵巢特异性 RNA-seq 来实现，而后者将基于亲本物种和 OP 分离株的等位基因特异性 RNA-seq 分析。为了显示差异表达和错误调节、RNAi 敲低和表型的候选基因将进行筛选以验证它们在 OP 中的功能作用，而 CRISPR/Cas9 编辑将用于确定每个基因的因果 SNP。最后，我们将通过引入 OP 因果 SNP 来重新创建 OP 动物使用 CRISPR/Cas9 编辑的 CP Daphnia pulex。

项目成果

期刊论文数量（11）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Delivery methods for CRISPR/Cas9 gene editing in crustaceans.

DOI：
10.1007/s42995-019-00011-4
发表时间：
2020-02
期刊：
Marine life science & technology
影响因子：
5.7
作者：
Xu S;Pham T;Neupane S
通讯作者：
Neupane S

The Transcriptomic Signature of Cyclical Parthenogenesis.

周期性孤立生成的转录组特征。

DOI：
10.1093/gbe/evad122
发表时间：
2023-07-03
期刊：
GENOME BIOLOGY AND EVOLUTION
影响因子：
3.3
作者：
Huynh, Trung Viet;Hall, Alexander S.;Xu, Sen
通讯作者：
Xu, Sen

An efficient method for hatching diapausing embryos of Daphnia pulex species complex (Crustacea, Anomopoda).

孵化水溞物种复合体（甲壳纲、无足纲）滞育胚胎的有效方法。

DOI：
10.1002/jez.2331
发表时间：
2020
期刊：
Journal of experimental zoology. Part A, Ecological and integrative physiology
影响因子：
0
作者：
Luu,DustinH-K;Vo,HillaryP;Xu,Sen
通讯作者：
Xu,Sen

Attachment and Release of Water Fleas' Ephippia on a Medium-Sized Waterfowl's Leg for Migration.

水蚤 Ephippia 在中型水禽腿上的附着和释放以进行迁徙。