Disentangling the complex karyotype evolution of crocuses

解开番红花复杂的核型进化

• 批准号: 465449547
• 负责人: Dr. Dörte Harpke
• 金额: --
• 依托单位: Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/465449547?language=en
• 关键词: Disentangling; complex; karyotype; evolution; crocuses

Dysploidy is assumed to be a main driver for re-diploidization after polyploidization and it could also be a driver of diversification by creating karyotype differences functioning as reproductive barriers. Our knowledge regarding these processes is, however, based on very few well-investigated examples and mechanistic explanations are yet lacking. The high frequency of dysploid chromosome number changes in the genus Crocus is unusual for plants with monocentric chromosomes. In extreme cases, the basic chromosome number was reduced from n = 15 to n = 4 within a few million years while doubling genome size at the same time. The sympatric and parapatric occurrence of closely related Crocus taxa without morphologically recognizable hybrids suggests that their different chromosome numbers might represent crossing barriers. However, molecular analysis already revealed the presence of homoploid hybridization in some Crocus groups despite parental species differing in their karyotypes. Therefore, in-detail population- and cytogenetic analyses are necessary to understand the role that different karyotypes and chromosome numbers might play in reproductive isolation and will add to clarify what mechanisms act at chromosome level. It is assumed that whole-genome duplication (WGD) triggers dysploidy. Thus, the initial identification of WGD events across the genus is crucial to correlate them with changed dysploidy frequencies. However, polyploidization cannot be deduced from mere chromosome numbers or genome sizes in Crocus. Instead, we will use k-mer frequencies of NGS data and identification of paralogous genes in transcriptome or shotgun sequences data of representatives of the relevant Crocus clades. (i) Once the clades with WGD events in the genus are identified, we can infer if and how fast dysploidy follows polyploidization and if single WGD events trigger multiple chromosomal rearrangements resulting eventually in species with different chromosome numbers.(ii) To trace dysploid karyotype changes, we will follow the fate of chromosomes/chromosome parts through dysploidy events by developing and employing chromosomal landscape markers in three selected species groups of Crocus.(iii) Crossing experiments will be set up in parallel to infer the influence of different (dysploid) karyotypes on the strengths of reproductive isolation or lack thereof. The proposed project will unravel the complex chromosome evolution of crocuses, give important insights in the role of dysploidy in plant evolution, and is aimed to establish the genus as model for mechanisms and regulation of dysploidy in monocentric plants.

异倍性被认为是多倍体化后再二倍体化的主要驱动力，它也可能是通过创造核型差异作为生殖障碍而实现多样化的驱动力。然而，我们关于这些过程的知识是基于非常少的经过充分研究的例子，而且还缺乏机械解释。番红花属植物染色体数目异常的频率高，这在单着丝粒染色体植物中是不寻常的。在极端的情况下，基本染色体数在几百万年内从n = 15减少到n = 4，同时基因组大小增加了一倍。同域和parapatric发生密切相关的番红花类群没有形态可识别的杂种表明，它们不同的染色体数目可能代表交叉障碍。然而，分子分析已经揭示了在一些番红花组中存在同倍体杂交，尽管亲本物种的核型不同。因此，详细的人口和细胞遗传学分析是必要的，以了解不同的核型和染色体数目可能在生殖隔离中发挥的作用，并将有助于澄清什么机制在染色体水平上发挥作用。据推测，全基因组复制（WGD）触发异倍性。因此，整个属的WGD事件的初始鉴定对于将它们与改变的异倍性频率相关联是至关重要的。然而，多倍体化不能仅仅从番红花的染色体数目或基因组大小推断。相反，我们将使用NGS数据的k聚体频率和相关番红花分支的代表的转录组或鸟枪序列数据中的旁系同源基因的鉴定。(i)一旦在该属中鉴定出具有WGD事件的进化枝，我们就可以推断异倍性是否以及多快地跟随多倍化，以及单个WGD事件是否触发多个染色体重排，最终导致具有不同染色体数目的物种。(ii)为了追踪异倍体核型变化，我们将通过在番红花的三个选定的物种组中开发和采用染色体景观标记来跟踪染色体/染色体部分通过异倍体事件的命运。(iii)平行进行杂交实验，以推断不同（异倍体）核型对生殖隔离强度或缺乏生殖隔离的影响。该项目将揭示番红花复杂的染色体进化，为植物进化中的异倍性作用提供重要见解，并旨在建立该属作为单中心植物异倍性机制和调控的模型。