Department of Biotechnology, Sangmyung University, Seoul, 03016, South Korea.
Department of Biotechnology, Sangmyung University, Seoul, 03016, South Korea.
Ecotoxicol Environ Saf. 2020 Jun 1;195:110474. doi: 10.1016/j.ecoenv.2020.110474. Epub 2020 Mar 19.
In the present study, we characterized the potential toxin genes for polyketide synthase (PKS) and saxitoxin (STX) biosynthesis using the transcriptomes of two non-STX producing dinoflagellates Amphidinium carterae and Prorocentrum micans. RNA sequencing revealed 94 and 166 PKS contigs in A. carterae and P. micans, respectively. We first detected type III PKS, which was closely related to bacteria. In addition, dozens of homologs of 20 STX biosynthesis genes were identified. Interestingly, the core STX-synthesizing genes sxtA and sxtB were only found in P. micans, whereas sxtD was detected in A. carterae alone. Bioinformatic analysis showed that the first two core genes (sxtA and sxtG) had a low sequence similarity (37.0-67.6%) and different domain organization compared to those of other toxigenic dinoflagellates, such as Alexandrium pacificum. These might result in the breakdown of the initial reactions in STX production and ultimately the loss of the ability to synthesize the toxins in both dinoflagellates. Our findings suggest that toxin-related PKS and sxt genes are commonly found in non-STX producing dinoflagellates. In addition to their involvement in the synthesis of toxins, our result indicates that genes may also have other molecular metabolic functions.
在本研究中，我们使用两种非产 STX 甲藻（Amphidinium carterae 和 Prorocentrum micans）的转录组，对聚酮合酶（PKS）和石房蛤毒素（STX）生物合成的潜在毒素基因进行了特征描述。RNA 测序分别在 A. carterae 和 P. micans 中发现了 94 个和 166 个 PKS 基因簇。我们首次检测到了与细菌密切相关的 III 型 PKS。此外，还鉴定了数十个 20 个 STX 生物合成基因的同源物。有趣的是，核心 STX 合成基因 sxtA 和 sxtB 仅在 P. micans 中发现，而 sxtD 仅在 A. carterae 中发现。生物信息学分析表明，前两个核心基因（sxtA 和 sxtG）与其他产毒甲藻（如太平洋亚历山大藻）相比，序列相似性（37.0-67.6%）和结构域组织均较低。这可能导致 STX 产生的初始反应中断，最终导致两种甲藻丧失合成毒素的能力。我们的研究结果表明，毒素相关的 PKS 和 sxt 基因在非产 STX 甲藻中普遍存在。除了参与毒素合成外，我们的结果还表明这些基因可能具有其他分子代谢功能。
