Hackett Jeremiah D, Yoon Hwan Su, Soares M Bento, Bonaldo Maria F, Casavant Thomas L, Scheetz Todd E, Nosenko Tetyana, Bhattacharya Debashish
Department of Biological Sciences and Center for Comparative Genomics, The University of Iowa, Iowa City, IA 52242, USA.
Curr Biol. 2004 Feb 3;14(3):213-8. doi: 10.1016/j.cub.2004.01.032.
Dinoflagellate algae are important primary producers and of significant ecological and economic impact because of their ability to form "red tides". They are also models for evolutionary research because of an unparalleled ability to capture photosynthetic organelles (plastids) through endosymbiosis. The nature and extent of the plastid genome in the dominant perdinin-containing dinoflagellates remain, however, two of the most intriguing issues in plastid evolution. The plastid genome in these taxa is reduced to single-gene minicircles encoding an incomplete (until now 15) set of plastid proteins. The location of the remaining photosynthetic genes is unknown. We generated a data set of 6,480 unique expressed sequence tags (ESTs) from the toxic dinoflagellate Alexandrium tamarense (for details, see the Experimental Procedures in the Supplemental Data) to find the missing plastid genes and to understand the impact of endosymbiosis on genome evolution. Here we identify 48 of the non-minicircle-encoded photosynthetic genes in the nuclear genome of A. tamarense, accounting for the majority of the photosystem. Fifteen genes that are always found on the plastid genome of other algae and plants have been transferred to the nucleus in A. tamarense. The plastid-targeted genes have red and green algal origins. These results highlight the unique position of dinoflagellates as the champions of plastid gene transfer to the nucleus among photosynthetic eukaryotes.
甲藻是重要的初级生产者，因其能够形成“赤潮”而具有重大的生态和经济影响。它们也是进化研究的模式生物，因为它们具有通过内共生捕获光合细胞器（质体）的无与伦比的能力。然而，在占主导地位的含多甲藻素的甲藻中，质体基因组的性质和范围仍然是质体进化中最引人入胜的两个问题。这些分类群中的质体基因组已简化为编码一组不完整（截至目前为15个）质体蛋白的单基因微环。其余光合基因的位置尚不清楚。我们从有毒甲藻塔玛亚历山大藻中生成了一个包含6480个独特表达序列标签（EST）的数据集（详情见补充数据中的实验步骤），以寻找缺失的质体基因，并了解内共生对基因组进化的影响。在这里，我们在塔玛亚历山大藻的核基因组中鉴定出48个非微环编码的光合基因，占光合系统的大部分。在其他藻类和植物的质体基因组中一直存在的15个基因已转移到塔玛亚历山大藻的细胞核中。这些质体靶向基因具有红藻和绿藻的起源。这些结果突出了甲藻在光合真核生物中作为质体基因向细胞核转移的冠军的独特地位。
