Microbial Genome Sequencing: An EST Approach to Understanding Endosymbiotic Gene Transfer

爱荷华大学的Debashish Bhattacharya获得了一笔拨款，用于从有毒的甲藻亚历山大藻（Alexandrium tamarense）和亲藻埃米利亚纳·赫胥利（Emiliana huxleyi）中创建表达基因的基因组资源（ESTs）。EST数据将用于了解内共生在驱动核基因组进化中的作用。内共生，单细胞原生生物吞噬并“奴役”另一个细胞的光合细胞器（质体），解释了大多数藻类的起源。质体内共生必然改变“宿主”谱系，因为外源基因从捕获的内共生体大规模移动到宿主细胞核。这个过程被称为内共生基因转移，是质体功能所必需的。尽管它对细胞进化很重要，但对内共生基因转移的理解还处于起步阶段。为了获得对这一过程的基本见解，本研究使用了基因组学方法，通过测序来自亚历山大和埃米利亚尼亚的30,000个est。高质量的表达基因文库用于高效的“基因发现”策略，以生成全面的藻类ESTs集合。利用这些技术，将从每种藻类中产生大约10,000种独特的est。这些数据将成为了解内共生基因转移的基础，并将为对藻类进化、有害藻华（HABs）中的毒素产生、碳循环和遗传学等主题感兴趣的科学家提供广泛的社区，为研究具有高度经济和生态重要性的两个分类群的生物学提供宝贵的资源。亚历山大菌在沿海地区引起有害藻华，导致麻痹性贝类中毒，而埃米利亚菌在海洋开放水域占主导地位，其颗石藻阶段是地球上主要的碳汇。这是一个微生物基因组测序奖，由国家科学基金会和农业部合作项目资助。

Debashish Bhattacharya of the University of Iowa has been awarded a grant to create a genomic resource of expressed genes (ESTs) from the toxic dinoflagellate alga Alexandrium tamarense and the haptophyte alga Emiliana huxleyi. The EST data will be used to understand the role of endosymbiosis in driving nuclear genome evolution. Endosymbiosis, in which a single-celled protist engulfs and "enslaves" the photosynthetic organelle (plastid) of another cell, explains the origin of most algae. Plastid endosymbiosis necessarily changes the "host" lineage because of the large scale movement of foreign genes from the captured endosymbiont to the host nucleus. This process, known as endosymbiotic gene transfer, is required for plastid function. Despite its importance to cellular evolution, the understanding of endosymbiotic gene transfer is in its infancy. To gain fundamental insights into this process, a genomics approach is used in this research through the sequencing of 30,000 ESTs from Alexandrium and Emiliania. High-quality libraries of expressed genes are used in an efficient "gene discovery" strategy to generate a comprehensive collection of algal ESTs. Using these techniques, about 10,000 unique ESTs from each algal species will be produced. These data will be the basis for understanding endosymbiotic gene transfer and will provide a broad community of scientists interested in topics such as algal evolution, toxin production in harmful algal blooms (HABs), carbon cycling, and genetics with an invaluable resource for studying the biology of two taxa that are of high economic and ecological importance. Alexandrium causes HABs in coastal areas resulting in paralytic shellfish poisoning, whereas Emiliania is dominant in oceanic open waters where its coccolithophore phase acts as a major carbon sink on the planet. This is a Microbial Genome Sequencing Award funded through a collaborative program between the National Science Foundation and the Department of Agriculture.