MOLECULAR AND DEVELOPMENTAL APPROACH TO TWO MAJOR TRANSITIONS IN DIATOM EVOLUTION.

硅藻进化中两个主要转变的分子和发育方法。

• 批准号: RGPIN-2014-06513
• 负责人: Kaczmarska, Irena
• 金额: $ 2.48万
• 依托单位: Mount Allison University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=589059
• 关键词: MOLECULAR; DEVELOPMENTAL; APPROACH; TWO; MAJOR

Diatoms (microscopic marine plants) are tremendously important ecologically (the oxygen in every fifth breath we take comes from diatoms) and economically (some produce neurotoxins harmful to humans). They are also the most species rich group of microalgae (~200,000 species) – thus rivalling the richness and diversity of flowering plants on land. Evolutionarily, like flowering plants, diatoms also are relatively new arrivals, suggesting a high rate of speciation. Unlike flowering plants, however, the mechanism(s) of speciation in diatoms is unknown. The long term objective of my research is to evaluate the evolutionary significance of diatom sex and related structures, and to better understand what role various types of sexuality play in the spectacular diversification of diatoms since their first appearance in the Jurassic Period fossil record. The immediate objectives specific to this proposal are to apply developmental and molecular approaches to representatives of two major lineages of diatoms in key evolutionary positions: the basal non-polar centrics (earliest branches in diatom phylogeny) and basal araphid pennates (deepest split among the most derived diatoms, the pennates). We will use monoclonal cultures already at hand and establish many more from local and distant geographies to develop robust and densely sampled “family trees” (phylogenies) for these lineages. We will use advanced microscopical techniques (epifluorescence and deconvolution light microscopy, scanning electron microscopy, x-ray microanalysis, silica-specific stains) to detect and localise opaline silica (the building blocks of diatom cell walls) and describe the fine structure of the cell-wall components during their stages of development. Determination of mating compatibility and behavioural expression of sex (e.g., unisexual, polysexual) will provide new insights into the propensity for in- vs. out-breeding among the pennates, thereby facilitating predictions about the intra- and interspecific genetic variability of these diatoms, and ultimately testable predictions about mechanisms of diatom speciation. Results from this study of diatom sexual structures and mating behaviour will be integrated into phylogenies of the diatom groups delineated by analysis of selected DNA sequences. Phylogenetic analysis of these diatoms combined with comparative developmental approaches we propose here are novel in diatom evolutionary biology, which we pioneered only about decade ago. The major obstacle to further advancement was the lack of reproducible sex-induction protocols which we now have for the diatom groups involved. The results of this work will provide a multipronged framework to better our understanding of major evolutionary transitions in diatoms and allow us to characterize species boundaries at a biological (sex-compatibility) and molecular level. The proposed work includes numerous new training opportunities, including advanced microscopy and phylogenetic projects for undergraduate researchers and more advanced students.

硅藻（微小的海洋植物）在生态学（我们每五次呼吸中的氧气都来自硅藻）和经济学（一些产生对人类有害的神经毒素）上都非常重要。它们也是种类最丰富的微藻群（约20万种），因此可以与陆地上开花植物的丰富性和多样性相媲美。在进化上，像开花植物一样，硅藻也是相对较新的物种，表明物种形成的速度很高。然而，与开花植物不同，硅藻的物种形成机制尚不清楚。 我的研究的长期目标是评估硅藻性别和相关结构的进化意义，并更好地了解自侏罗纪化石记录首次出现以来，各种类型的性别在硅藻的壮观多样化中发挥了什么作用。该提案的直接目标是将发展和分子方法应用于关键进化位置的硅藻的两个主要谱系的代表：基底非极性中心（硅藻发育中最早的分支）和基底araphid pennates（最衍生的硅藻之间最深的分裂，pennates）。我们将使用现有的单克隆培养，并从本地和遥远的地理位置建立更多的单克隆培养，为这些谱系建立强大的和密集采样的“家谱”（家系）。 我们将使用先进的显微镜技术（落射荧光和去卷积光学显微镜，扫描电子显微镜，X射线显微分析，二氧化硅特异性染色）来检测和定位乳白色二氧化硅（硅藻细胞壁的构建块），并描述细胞壁组件在其发展阶段的精细结构。确定交配相容性和性别的行为表达（例如，单性，多性）将提供新的见解的倾向，内与外繁殖的羽状幼体，从而促进预测的内部和种间的遗传变异，这些硅藻，并最终可测试的预测机制硅藻物种形成。硅藻性别结构和交配行为的研究结果将被整合到通过分析选定的DNA序列描绘的硅藻群体的遗传学中。 这些硅藻的系统发育分析结合比较发展的方法，我们在这里提出的硅藻进化生物学，我们开创了只有大约十年前是新颖的。进一步发展的主要障碍是缺乏可重复的性别诱导协议，我们现在所涉及的硅藻群体。这项工作的结果将提供一个多管齐下的框架，以更好地了解硅藻的主要进化转变，并使我们能够在生物（性别相容性）和分子水平上表征物种边界。拟议的工作包括许多新的培训机会，包括为本科研究人员和更先进的学生提供先进的显微镜和系统发育项目。