Spermatogenesis in "Pteridophytes": Ultrastructure Differentiation and Phylogeny

小行星9527735 早期生命形式从水到陆地的首次成功迁移是所有生物事件中最重要和最令人困惑的事件之一。 近5亿年前，沼泽藻类登上了陆地，从而为动植物的蓬勃发展奠定了基础。 然而，仍然不确定这种祖先的样子，以及今天存在的各种植物群与这种假定的祖先以及彼此之间的关系。 本计画拟借由研究无籽维管植物--蕨类植物的精细胞发育与结构，来探讨这些基本问题。 蕨类植物包括蕨类植物、石松、穗状苔藓、鹅掌楸和木贼。 现代蕨类植物中的精细胞为古代陆地植物的功能、结构和进化提供了线索。 游动精子是当代植物中唯一的能动细胞，因此它们携带着水生藻类祖先的特征。 追踪它们的分化和结构为早期陆地植物谱系提供了线索，并最终确定了一直追溯到祖先藻类的进化线索。 10个OpteridophytesO，其精子细胞被认为最接近的第一个陆地生物的物种，将有针对性的电子显微镜检查。 将为每株植物拍摄500多张详细的显微照片。 将对这些照片进行分析，并制作三维图像，以描绘发展阶段。 此外，计算机将跟踪和分析大约100种细胞特征的信息，从细胞形状到蛋白质成分。 重点将放在检查蛋白质的作用，参与组织这些高度复杂的运动细胞的结构实体。 这一结果将有助于把这10个信息丰富的物种更准确地放在植物世界的复杂谱系树上。 这些分析也将更清楚地解决现代藻类是最接近的亲戚，陆生植物和原始植物群的出现顺序在早期历史的植物生活在陆地上。 除此之外，这些研究还提供了有关所有生命形式中细胞的组织，分化和进化的更多重要信息。

9527735 RENZAGLIA The first successful migration of early life forms from water to land was one of the most significant and perplexing of all biological events. Nearly 500 million years ago, swamp-dwelling algae made it ashore and thus set the stage for the magnificent flourish of plants and animals to come. Yet, it is still uncertain as to what this ancestral alga looked like and how the diverse plant groups that exist today are related to this presumed ancestor, and to each other. This project proposes to address these fundamental questions by examining sperm cell development and structure in a critical group of seedless vascular plants, the OpteridophytesO. Plants included among the OpteridophytesO include ferns, club mosses, spike mosses, quillworts, and horsetails. Sperm cells in modern OpteridophytesO hold clues to the functioning, structure and evolution of ancient land plants. Swimming sperm are the only motile cells of contemporary plants and as such they carry traits of their aquatic algal ancestors. Tracing their differentiation and architecture provides clues to early land plant lineages and will eventually identify evolutionary threads leading all the way back to the ancestral algae. Ten OpteridophytesO, species whose sperm cells are thought to resemble most closely those of the first terrestrial organisms, will be targeted for electron microscopic examination. More than 500 detailed micrographs will be taken for each plant. These photographs will be analyzed and three-dimensional images will be prepared to depict the stages of development. In addition, computers will track and analyze information on approximately 100 cell traits, from cell shape to protein components. Emphasis will be placed on examining the role of proteins that are involved in organizing the structural entities of these highly complicated motile cells. The results will help place these ten informative species more correctly on the plant worldOs complex genealogical tree. These analyses will also more clearly resolve which modern algae are the closest relatives to terrestrial plants and the sequence of appearance of the primitive plant groups during the early history of plant life on land. Beyond that, these studies provide more essential information about the organization, differentiation and evolution of cells in all forms of life.