Shelest Ekaterina, Heimerl Natalie, Fichtner Maximilian, Sasso Severin
Research Group Systems Biology/Bioinformatics, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstr. 11a, 07745, Jena, Germany.
Institute of General Botany and Plant Physiology, Friedrich Schiller University, Dornburger Str. 159, 07743, Jena, Germany.
BMC Genomics. 2015 Nov 26;16:1015. doi: 10.1186/s12864-015-2222-9.
Polyketide synthase (PKS) catalyzes the biosynthesis of polyketides, which are structurally and functionally diverse natural products in microorganisms and plants. Here, we have analyzed available full genome sequences of microscopic and macroscopic algae for the presence of type I PKS genes.
Type I PKS genes are present in 15 of 32 analyzed algal species. In chlorophytes, large proteins in the MDa range are predicted in most sequenced species, and PKSs with free-standing acyltransferase domains (trans-AT PKSs) predominate. In a phylogenetic tree, PKS sequences from different algal phyla form clades that are distinct from PKSs from other organisms such as non-photosynthetic protists or cyanobacteria. However, intermixing is observed in some cases, for example polyunsaturated fatty acid (PUFA) and glycolipid synthases of various origins. Close relationships between type I PKS modules from different species or between modules within the same multimodular enzyme were identified, suggesting module duplications during evolution of algal PKSs. In contrast to type I PKSs, nonribosomal peptide synthetases (NRPSs) are relatively rare in algae (occurrence in 7 of 32 species).
Our phylogenetic analysis of type I PKSs in algae supports an evolutionary scenario whereby integrated AT domains were displaced to yield trans-AT PKSs. Together with module duplications, the displacement of AT domains may constitute a major mechanism of PKS evolution in algae. This study advances our understanding of the diversity of eukaryotic PKSs and their evolutionary trajectories.
聚酮合酶（PKS）催化聚酮化合物的生物合成，聚酮化合物是微生物和植物中结构和功能多样的天然产物。在此，我们分析了微观和宏观藻类的可用全基因组序列中I型PKS基因的存在情况。
在32种分析的藻类物种中有15种存在I型PKS基因。在绿藻中，大多数测序物种预测有兆道尔顿范围内的大蛋白，且具有独立酰基转移酶结构域的PKS（反式-AT PKS）占主导。在系统发育树中，来自不同藻类门的PKS序列形成与来自其他生物（如非光合原生生物或蓝细菌）的PKS不同的进化枝。然而，在某些情况下观察到了混合现象，例如各种来源的多不饱和脂肪酸（PUFA）和糖脂合酶。鉴定出不同物种的I型PKS模块之间或同一多模块酶内的模块之间存在密切关系，这表明藻类PKS进化过程中发生了模块重复。与I型PKS不同，非核糖体肽合成酶（NRPS）在藻类中相对较少（32种中有7种出现）。
我们对藻类I型PKS的系统发育分析支持一种进化情景，即整合的AT结构域被取代以产生反式-AT PKS。与模块重复一起，AT结构域的取代可能构成藻类中PKS进化的主要机制。这项研究推进了我们对真核生物PKS多样性及其进化轨迹的理解。
