Moreau Hervé, Verhelst Bram, Couloux Arnaud, Derelle Evelyne, Rombauts Stephane, Grimsley Nigel, Van Bel Michiel, Poulain Julie, Katinka Michaël, Hohmann-Marriott Martin F, Piganeau Gwenael, Rouzé Pierre, Da Silva Corinne, Wincker Patrick, Van de Peer Yves, Vandepoele Klaas
Genome Biol. 2012 Aug 24;13(8):R74. doi: 10.1186/gb-2012-13-8-r74.
Bathycoccus prasinos is an extremely small cosmopolitan marine green alga whose cells are covered with intricate spider's web patterned scales that develop within the Golgi cisternae before their transport to the cell surface. The objective of this work is to sequence and analyze its genome, and to present a comparative analysis with other known genomes of the green lineage.
Its small genome of 15 Mb consists of 19 chromosomes and lacks transposons. Although 70% of all B. prasinos genes share similarities with other Viridiplantae genes, up to 428 genes were probably acquired by horizontal gene transfer, mainly from other eukaryotes. Two chromosomes, one big and one small, are atypical, an unusual synapomorphic feature within the Mamiellales. Genes on these atypical outlier chromosomes show lower GC content and a significant fraction of putative horizontal gene transfer genes. Whereas the small outlier chromosome lacks colinearity with other Mamiellales and contains many unknown genes without homologs in other species, the big outlier shows a higher intron content, increased expression levels and a unique clustering pattern of housekeeping functionalities. Four gene families are highly expanded in B. prasinos, including sialyltransferases, sialidases, ankyrin repeats and zinc ion-binding genes, and we hypothesize that these genes are associated with the process of scale biogenesis.
The minimal genomes of the Mamiellophyceae provide a baseline for evolutionary and functional analyses of metabolic processes in green plants.
普拉西诺球藻是一种极小的世界性海洋绿藻，其细胞覆盖着错综复杂的蜘蛛网图案鳞片，这些鳞片在高尔基体池中形成后再运输到细胞表面。这项工作的目的是对其基因组进行测序和分析，并与绿色谱系的其他已知基因组进行比较分析。
其15兆碱基的小基因组由19条染色体组成，且缺乏转座子。尽管所有普拉西诺球藻基因的70%与其他绿藻门植物基因有相似性，但多达428个基因可能是通过水平基因转移获得的，主要来自其他真核生物。有两条染色体，一条大的和一条小的，是非典型的，这是小球藻目内一个不寻常的共有衍征。这些非典型异常染色体上的基因显示出较低的GC含量以及相当一部分推测的水平基因转移基因。小的异常染色体与其他小球藻目缺乏共线性，并且包含许多在其他物种中没有同源物的未知基因，而大的异常染色体显示出更高的内含子含量、更高的表达水平以及管家功能的独特聚类模式。四个基因家族在普拉西诺球藻中高度扩增，包括唾液酸转移酶、唾液酸酶、锚蛋白重复序列和锌离子结合基因，我们推测这些基因与鳞片生物合成过程有关。
小球藻科的最小基因组为绿色植物代谢过程的进化和功能分析提供了一个基线。
