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

0128952 Fawley三个研究团队(塔尔萨大学的Buchheim、北达科他州立大学的Fawley和加州州立大学弗雷斯诺分校的Zechman)已经开始合作，解决绿藻种群之间的等级(即系统发育)关系问题，这些绿藻种群统称为绿藻门。绿藻门在林奈命名系统中具有门的地位，它代表了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。绿藻包括从微观到宏观的各种生物体，表现出各种生殖策略(例如有性繁殖和无性繁殖)，并生活在广泛的生境(例如淡水、咸水和陆地)中。目前主要基于比较形态的绿藻门分类方案的某些方面受到了来自比较分子数据的新证据的挑战。然而，对新证据的全面解释还没有到来，因为(1)这些新的分子数据并没有应用于绿藻中的所有类群，(2)在大多数情况下，只有一个基因被用来评估选定的绿藻类群的多样性(不像陆地植物，在某些类群中的多样性是使用三个或更多不同的基因来研究的)。该项目的目的是通过对三个不同基因--核18S核糖体RNA和26S核糖体RNA基因以及叶绿体rbcL基因的DNA序列数据的比较研究，对绿藻的多样性进行全面的评估。这两个rRNA基因编码活细胞中发现的所有核糖体的一部分。RbcL基因是叶绿体基因组的一部分，编码植物中负责固碳的酶的一部分。CSU-Fresno的Zechman实验室将负责收集被称为Ulvophyceae的绿藻群体的数据。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的绿藻群体的数据。塔尔萨大学的布赫海姆实验室小组将从两个绿藻类群--树叶藻类和绿藻类群--收集数据。该项目的最终结果将是：(1)对绿藻的所有分子数据进行系统发育综合；(2)对绿藻分类进行根本性的重新评估，整合形态和光合色素数据；(3)将叶绿素分子系统发育数据与(公布的)陆地植物谱系的平行数据进行整合。利用绿藻作为模式生物的研究(例如，衣藻属，很容易在实验室中培养)极大地促进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化基础，将探索新的绿藻模型，以了解与这些现象相关的变异光谱。更全面地了解所有叶绿素类群之间的关系对于解释作为模式生物的叶绿素植物研究的结果(例如，评估更广泛的适用性)至关重要。此外，对绿藻多样性的全面评估结果将为未来依赖绿藻建立机制模型的生物过程研究提供信息。最后，研究绿藻门内的多样性对于促进我们对绿色植物谱系的起源和进化的理解至关重要。

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.