Dissertation Research: Chloroplast Evolution of the Nonphotosynthetic Liverwort Cryptothallus Mirabilis (Aneuraceae)

论文研究：非光合地钱Cryptothallus Mirabilis（Aneuraceae）的叶绿体进化

• 批准号: 0408043
• 负责人: Bernard Goffinet
• 金额: $ 1.15万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-15 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408043&HistoricalAwards=false
• 关键词: Dissertation; Research; Chloroplast; Evolution; Nonphotosynthetic

AbstractWithin bryophytes (mosses, liverworts, and hornworts), fungal associations are common only in hornworts and liverworts; however, only among liverworts is there a species that relies entirely on its fungal associate, rather than on photosynthesis, for fixed carbon. This dependence on an alternative carbon source is present only in one genus (two species) of liverworts: Cryptothallus (Aneuraceae). Cryptothallus mirabilis is non-photosynthetic, lacks the green pigment chlorophyll, and is therefore whitish yellow in appearance. Carbon is taken up from the fungus, which penetrates the intercellular spaces of the liverwort. The fungus, Tulasnella, satisfies its carbon demand through and ectomycorrhizal association with pine or birch trees. Among flowering plants, the evolution of a non-photosynthetic life strategy is accompanied by a reduction in the chloroplast genome. This reduction results in the loss (physically, or loss of function) of genes that code for enzymes involved in the reactions of photosynthesis. This award will support the dissertation research of a graduate student of Dr. Bernard Goffinet, Norman Wickett, investigating whether the patterns of gene loss observed in non-photosynthetic angiosperms are also present in non-flowering land plants, particularly bryophytes. To accomplish this, the complete chloroplast genome of C. mirabilis will be sequenced, as well as that of a closely related photosynthetic relative. Phylogenetic reconstruction will be used to identify the most closely related photosynthetic liverwort and to test hypotheses of genomic evolution. Comparisons can then be made between the two chloroplast genomes in order to identify changes associated with the loss of photosynthesis and to test hypotheses of genomic evolution. Chloroplast genome sequences will be obtained using a modified shotgun sequencing method developed for non-photosynthetic flowering plants.This study integrates genomics and phylogenetics in order to assess patterns of chloroplast genome evolution in a non-photosynthetic bryophyte. Much of the current understanding in this area arises from studies of flowering plants; this study, therefore, will significantly broaden the taxonomic diversity of studies addressing chloroplast genome evolution accompanying the loss of one of the most fundamental processes of life: photosynthesis. The results of this study will be made available to the public and the scientific community. In the latter case, the results will be particularly informative to current studies addressing the evolution of land plants in general. The unique natural history of this study, and the fundamental nature of its focal questions (genomic evolution when major selection forces are lost), should facilitate the dissemination of findings through local outreach activities and publications in popular journals.

在苔藓类（苔藓、地钱和金鱼藻）中，真菌共生仅在金鱼藻和地钱中常见;然而，只有在地钱中才有一个物种完全依赖其真菌共生体而不是光合作用来固定碳。这种对替代碳源的依赖只存在于一个属（两个物种）的苔类：隐藻（Aneuraceae）。 奇异隐藻是非光合作用的，缺乏绿色色素叶绿素，因此外观呈白黄色。碳从真菌中吸收，穿透苔类植物的细胞间隙。真菌Tulasnella通过与松树或桦树的外生菌根结合来满足其碳需求。在开花植物中，非光合作用生命策略的进化伴随着叶绿体基因组的减少。这种减少导致编码参与光合作用反应的酶的基因的损失（物理或功能损失）。该奖项将支持Bernard Goffinet博士的研究生Norman Wickett的论文研究，调查在非光合被子植物中观察到的基因丢失模式是否也存在于非开花的陆地植物中，特别是brittes。为了实现这一点，完整的叶绿体基因组C。将对紫茉莉以及一种与光合作用密切相关的亲缘植物进行测序。系统发育重建将被用来确定最密切相关的光合苔和测试的基因组进化的假设。然后可以在两个叶绿体基因组之间进行比较，以确定与光合作用丧失相关的变化，并测试基因组进化的假设。叶绿体基因组序列的获得将使用一种改进的鸟枪测序方法开发的非光合开花plants.This研究整合基因组学和植物遗传学，以评估模式的叶绿体基因组的进化在非光合branchete。目前在这一领域的大部分认识来自显花植物的研究，因此，这项研究将显着扩大分类多样性的研究解决叶绿体基因组进化伴随着生命的最基本的过程之一的损失：光合作用。这项研究的结果将提供给公众和科学界。在后一种情况下，其结果将特别提供信息，目前的研究解决一般的陆地植物的进化。这项研究独特的自然历史，以及其焦点问题的基本性质（主要选择力量丧失时的基因组进化），应有助于通过当地的外联活动和在流行杂志上发表文章传播研究结果。