Alfred-Wegener-Institut für Polar-und Meeresforschung, Bremerhaven, Germany.
BMC Genomics. 2010 Apr 19;11:248. doi: 10.1186/1471-2164-11-248.
The dinoflagellate Alexandrium minutum typically produces paralytic shellfish poisoning (PSP) toxins, which are known only from cyanobacteria and dinoflagellates. While a PSP toxin gene cluster has recently been characterized in cyanobacteria, the genetic background of PSP toxin production in dinoflagellates remains elusive.
We constructed and analysed an expressed sequence tag (EST) library of A. minutum, which contained 15,703 read sequences yielding a total of 4,320 unique expressed clusters. Of these clusters, 72% combined the forward-and reverse reads of at least one bacterial clone. This sequence resource was then used to construct an oligonucleotide microarray. We analysed the expression of all clusters in three different strains. While the cyanobacterial PSP toxin genes were not found among the A. minutum sequences, 192 genes were differentially expressed between toxic and non-toxic strains.
Based on this study and on the lack of identified PSP synthesis genes in the two existent Alexandrium tamarense EST libraries, we propose that the PSP toxin genes in dinoflagellates might be more different from their cyanobacterial counterparts than would be expected in the case of a recent gene transfer. As a starting point to identify possible PSP toxin-associated genes in dinoflagellates without relying on a priori sequence information, the sequences only present in mRNA pools of the toxic strain can be seen as putative candidates involved in toxin synthesis and regulation, or acclimation to intracellular PSP toxins.
塔玛亚历山大藻通常产生麻痹性贝类毒素（PSP）毒素，这种毒素仅存在于蓝藻和甲藻中。虽然最近在蓝藻中已鉴定出 PSP 毒素基因簇，但甲藻中 PSP 毒素产生的遗传背景仍不清楚。
我们构建并分析了塔玛亚历山大藻的表达序列标签（EST）文库，该文库包含 15703 条读序列，共产生了 4320 个独特的表达簇。这些簇中，72%的簇结合了至少一个细菌克隆的正向和反向读序列。然后，我们利用这个序列资源构建了一个寡核苷酸微阵列。我们分析了三种不同菌株中所有簇的表达情况。虽然在塔玛亚历山大藻序列中未发现蓝藻的 PSP 毒素基因，但在有毒和无毒菌株之间有 192 个基因表达存在差异。
基于这项研究以及在两个现存的塔玛亚历山大藻 EST 文库中未鉴定出 PSP 合成基因这一事实，我们提出，甲藻中的 PSP 毒素基因可能与其蓝藻对应物的差异比最近基因转移时预期的更大。作为在不依赖先验序列信息的情况下识别甲藻中可能与 PSP 毒素相关的基因的起点，可以将仅存在于有毒株 mRNA 池中的序列视为可能参与毒素合成和调控或适应细胞内 PSP 毒素的候选基因。
