Collaborative Research: A Multi-Gene Approach to Chlorophytan Phylogeny and Diversity

0128952Fawley三个研究小组（塔尔萨大学的Buchheim，北达科他州州立大学的Fawley和弗雷斯诺的加州州立大学的Zechman）已经开始了一项合作，将解决有关分层的问题（即，系统发育）之间的关系，统称为绿藻门的绿色藻类群体。 绿藻门在林奈命名系统中具有门的地位，代表绿色植物谱系的两个分支之一，另一个分支是陆地植物联盟。 绿藻门包括范围从微观到宏观的生物体，表现出多种生殖策略（例如，有性与无性），并且生活在广泛的栖息地（例如，淡水、咸水和陆地）。目前的分类方案的绿藻，主要是基于比较形态学的一些方面，已受到挑战的新证据，从比较分子数据。 然而，对新证据的全面解释尚未出现，因为（1）这些新的分子数据尚未应用于绿藻门内的所有群体，（2）在大多数情况下，只有一个基因被用于评估绿藻门中选定群体的多样性（不像陆地植物，其中一些群体的多样性已经使用三个或更多个不同的基因进行了研究）。 该项目的目标是开发一个全面的评估的多样性在绿藻门中使用的DNA序列数据在三个不同的基因，核18S核糖体RNA和26S核糖体RNA基因，和叶绿体rbcL基因的比较研究。 这两个rRNA基因编码活细胞中所有核糖体的一部分。 rbcL基因是叶绿体基因组的一部分，编码植物中负责碳固定的酶的一部分。 加州大学弗雷斯诺分校的Zechman实验室将负责收集被称为Ulvophyceae的绿藻群的数据。 北达科他州州立大学的Fawley实验室小组将负责收集被称为Prasinophyceae的绿藻群的数据。 塔尔萨大学的Buchheim实验室小组将收集来自两个绿藻类群Trebouxiophyceae和Chlorophyceae的数据。 该项目将最终在（1）所有分子数据的系统发育合成的绿藻，（2）一个根本的重新评估的绿藻分类，整合形态和光合色素数据，和（3）整合的绿藻分子系统发育数据与（已公布的）平行数据从陆地植物谱系。利用绿藻绿色藻类作为模式生物（例如，在实验室中容易培养的衣原体属）的研究大大提高了我们对光合作用和鞭毛功能等基本过程的理解。 随着生物学家继续剖析生物现象的分子和生物化学基础，将探索新的绿藻模型，以了解与这些现象相关的变化谱。 更全面地了解所有绿藻群之间的关系将是至关重要的解释结果（例如，评估更广泛的适用性）从绿藻作为模式生物的研究。 此外，从一个全面的评估结果的绿藻多样性将告知未来的研究生物过程中，依赖于绿色藻类模型的机制。 最后，绿藻门内多样性的研究是至关重要的，以推进我们的理解的起源和进化的绿色植物谱系。

0128952FawleyThree research teams (Buchheim at University of Tulsa, Fawley at North Dakota State University, and Zechman at California State University at Fresno) have begun a collaboration that will address questions about the hierarchical (i.e., phylogenetic) relationships among green algal groups that are collectively known as the Chlorophyta. The Chlorophyta, which has phylum status in the Linnean nomenclatural system, represents one of two branches of the green plant lineage-the other branch being the land plant alliance. The Chlorophyta comprise organisms that range from the microscopic to the macroscopic, exhibit a variety of reproductive strategies (e.g., sexual vs. asexual), and live in a broad spectrum of habitats (e.g., freshwater, saltwater and terrestrial). Some aspects of the current classification scheme for the Chlorophyta, based largely on comparative morphology, have been challenged by new evidence from comparative molecular data. A comprehensive interpretation of the new evidence, however, has not been forthcoming because (1) these new molecular data have not been applied to all groups within the Chlorophyta and (2) in most cases only a single gene has been used to evaluate diversity among select groups of Chlorophyta (unlike the land plants where diversity in some groups has been studied using three or more different genes). The goal of this project is to develop a comprehensive assessment of diversity in the Chlorophyta using a comparative study of DNA sequence data in three different genes, the nuclear 18S ribosomal RNA and 26S ribosomal RNA genes, and the chloroplast rbcL gene. The two rRNA genes code for portions of all ribosomes found in living cells. The rbcL gene is part of the chloroplast genome and codes for a portion of the enzyme responsible for carbon fixation in plants. The Zechman lab at CSU-Fresno will be responsible for gathering data from the chlorophyte group known as the Ulvophyceae. The Fawley lab group at North Dakota State University will be responsible for gathering data from the chlorophyte group known as the Prasinophyceae. The Buchheim lab group at the University of Tulsa will gather data from the two chlorophyte groups, Trebouxiophyceae and Chlorophyceae. The project will culminate in (1) a phylogenetic synthesis of all molecular data for the Chlorophyta, (2) a fundamental re-assessment of chlorophyte classification, integrating morphological and photosynthetic pigment data, and (3) an integration of the chlorophyte molecular phylogenetic data with (published) parallel data from the land plant lineage. Studies using chlorophyte green algae as model organisms (for example, the genus Chlamydomonas, easily cultured in the laboratory) have significantly advanced our understanding of fundamental processes such as photosynthesis and flagellar function. As biologists continue to dissect the molecular and biochemical basis for biological phenomena, new chlorophyte models will be explored in order to understand the spectrum of variation associated with these phenomena. A more comprehensive understanding of the relationships among all chlorophyte groups will be vital to interpreting the results (for example, assessing the broader applicability) from studies of chlorophytes used as model organisms. Moreover, the results from a comprehensive assessment of chlorophyte diversity will inform future studies of biological processes that rely on green algae to model the mechanisms. Lastly, studies of diversity within the Chlorophyta are critical to advancing our understanding of the origins and evolution of the green plant lineage.