In the present study, we extensively characterized potential toxin-related genes, including polyketide synthase (PKS), saxitoxin (STX) and fatty acid synthase (FAS) from the non-toxin producing marine dinoflagellate Cochlodinium polykrikoides, comparing to those of a toxigenic dinoflagellate Alexandrium pacificum. RNA sequencing revealed 50 and 271 PKS contigs from C. polykrikoides and A. pacificum, respectively. According to domain constitute and amino acid alteration, we further classified the dinoflagellate type I PKS genes into 4 sub-groups. Type III PKS was first identified in C. polykrikoides. Interestingly, we detected a large number (242 and 288) of homologs of 18 sxt genes from two studied dinoflagellates. Most of the eight key genes (sxtA, sxtB, sxtD, sxtG, sxtH/T, sxtI, sxtS and sxtU) for STX synthesis were detected in both dinoflatellates, whereas a core STX biosynthesis gene sxtG was not detected in C. polykrikoides. This may partially explain the absence of saxitoxin production in C. polykrikoides. In addition, we identified several type I and type II FAS genes, including FabD, FabF, FabG, FabH, FabI, and FabZ, whereas FabB was not found in C. polykrikoides. Overall, the numbers of the toxin-related genes in C. polykrikoides were less than that of A. pacificum. Phylogenetic analyses showed that type I PKS/FASs of dinoflagellates had close relationships with apicomplexans and bacteria. These suggest that the toxin-related PKS and sxt genes are commonly present in toxigenic and non-toxin producing dinoflagellates, and may be involved not only in the toxin synthesis, but also in other related molecular metabolic functions.

在本研究中，我们与产毒素的鞭毛鞭毛藻相比，广泛鉴定了潜在的与毒素相关的基因，包括来自非毒素的海洋鞭毛鞭毛科球藻多角蛋白中的聚酮化合物合酶（PKS），毒毒素（STX）和脂肪酸合酶（FAS）。亚历山大山。RNA测序显示分别来自多角假单胞菌和太平洋曲霉的50和271个PKS重叠群。根据结构域组成和氨基酸变化，我们进一步将鞭毛类I PKS基因分为4个亚组。III型PKS最先在多角衣藻中鉴定。有趣的是，我们检测到了18 sxt的大量同系物（242和288）来自两个研究过的鞭毛虫的基因。最八个关键基因（的的sxtA，SXTB，sxtD，sxtG，SXTH / T，sxtI，sxtS和sxtU），用于合成STX在两个dinoflatellates进行检测，而芯STX生物合成基因sxtG在未检测到C. polykrikoides。这可能部分解释了多角衣藻中缺乏毒素的产生。此外，我们鉴定了几种I型和II型FAS基因，包括FabD，FabF，FabG，FabH，FabI和FabZ，而在多角梭菌中未发现FabB。总体而言，多角衣藻中毒素相关基因的数量少于太平洋杆菌。系统发育分析表明，甲鞭毛虫的I型PKS / FAS与apicomplexans和细菌有密切的关系。这些表明与毒素相关的PKS和sxt基因通常存在于产毒和不产生毒素的鞭毛鞭毛藻中，并且不仅可能参与毒素合成，而且可能参与其他相关的分子代谢功能。