Pan Kehou, Qin Junjie, Li Si, Dai Wenkui, Zhu Baohua, Jin Yuanchun, Yu Wengong, Yang Guanpin, Li Dongfang
Key Laboratory of Mariculture of Chinese Ministry of Education, Ocean University of China, Qingdao 266003, China Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100029, China Graduate University of Chinese Academy of Sciences, Beijing 100049, China Beijing Genomics Institute (BGI) at Shenzhen, Shenzhen 518083, ChinaKey Laboratory of Marine Genetics and Breeding of Chinese Ministry of Education, Ocean University of China, Qingdao 266003, ChinaBeijing Genomics Institute (BGI) at Shenzhen, Shenzhen 518083, ChinaKey Laboratory of Mariculture of Chinese Ministry of Education, Ocean University of China, Qingdao 266003, ChinaBeijing Genomics Institute (BGI) at Shenzhen, Shenzhen 518083, ChinaCollege of Medicine and Drugs, Ocean University of China, Qingdao 266003, ChinaKey Laboratory of Marine Genetics and Breeding of Chinese Ministry of Education, Ocean University of China, Qingdao 266003, ChinaBeijing Genomics Institute (BGI) at Shenzhen, Shenzhen 518083, China.
J Phycol. 2011 Dec;47(6):1425-32. doi: 10.1111/j.1529-8817.2011.01057.x. Epub 2011 Sep 23.
Species in genus Nannochloropsis are promising candidates for both biofuel and biomass production due to their ability to accumulate rich fatty acids and grow fast; however, their sexual reproduction has not been studied. It is clear that the construction of their metabolic pathways, such as that of polyunsaturated fatty acid (PUFA) biosynthesis, and understanding of their biological characteristics, such as nuclear ploidy and reproductive strategy, will certainly facilitate their genetic improvement through gene engineering and mutation and clonal expansion. In this study, the genome of N. oceanica S. Suda et Miyashita was sequenced with the next-generation Illumina GA sequencing technologies. The genome was ∼30 Mb in size, which contained 11,129 protein-encoding genes. Of them, 59.65% were annotated by aligning with those in diverse protein databases, and 29.68% were assigned at least one function described in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Less frequent polymorphic nucleotides (one in 22.06 kb) and the obvious deviation from 1:1 (major:minor, minor ≥10) expectation indicated the nuclear monoploidy of N. oceanica. The lack of the majority of meiosis-specific proteins implied the asexual reproduction of this alga. In combination, the nuclear monoploidy and asexual propagation led us to favor the hypothesis that N. oceanica was a premeiotic or ameiotic alga. In addition, sequence similarity-based searching identified the elongase- and desaturase-encoding genes involved in the biosynthesis of long-chain PUFAs, which provided the genetic basis of its rich content of eicosapentaenoic acid (EPA). The functional genes and their metabolic pathways profiled against its genome sequence will facilitate its integrative investigations.
由于能够积累丰富的脂肪酸并快速生长，微绿球藻属的物种是生物燃料和生物质生产的有前景的候选者；然而，它们的有性生殖尚未得到研究。显然，构建它们的代谢途径，如多不饱和脂肪酸（PUFA）生物合成途径，以及了解它们的生物学特性，如核倍性和生殖策略，肯定会通过基因工程、突变和克隆扩增促进它们的遗传改良。在本研究中，利用下一代Illumina GA测序技术对海洋微绿球藻（N. oceanica S. Suda et Miyashita）的基因组进行了测序。该基因组大小约为30 Mb，包含11,129个蛋白质编码基因。其中，59.65%通过与不同蛋白质数据库中的序列比对得到注释，29.68%至少被赋予了京都基因与基因组百科全书（KEGG）数据库中描述的一种功能。较少出现的多态性核苷酸（每22.06 kb中有一个）以及明显偏离1:1（主要:次要，次要≥10）的预期表明海洋微绿球藻为单核单倍体。大多数减数分裂特异性蛋白的缺失意味着该藻类进行无性繁殖。综合来看，核单倍性和无性繁殖使我们倾向于认为海洋微绿球藻是一种减数分裂前或无减数分裂的藻类。此外，基于序列相似性的搜索鉴定出了参与长链PUFA生物合成的延长酶和去饱和酶编码基因，这为其丰富的二十碳五烯酸（EPA）含量提供了遗传基础。针对其基因组序列分析的功能基因及其代谢途径将有助于对其进行综合研究。
