基于产毒基因sxtA的qPCR方法在长江口邻近海域有毒藻类检测中的应用初探

麻痹性贝毒(paralytic shellfish toxins)包括石房蛤毒素(saxitoxin)及其同系物,是一类具有神经毒性的生物毒素,主要由甲藻和蓝藻产生。近年来,在蓝藻和甲藻中相继发现了一些与石房蛤毒素合成密切相关的基因,并建立了基于特定产毒基因的有毒藻类检测方法。长江口邻近海域是我国近海有害藻华的高发区,本研究尝试应用基于麻痹性贝毒产毒基因sxtA的qPCR检测方法,与有毒塔玛亚历山大藻复合种(I型和IV型)的qPCR检测方法和麻痹性贝毒的高效液相色谱方法相结合,对2013年春季长江口邻近海域两条断面上有毒藻和藻毒素的分布及变动情况进行了分析。结果表明,基于sxtA的qPCR检测结果与IV型塔玛亚历山大藻复合种的数量存在较好的相关性(r2=0.52,P0.05),说明IV型塔玛亚历山大藻复合种是采样期间长江口邻近海域麻痹性贝毒的主要来源;而样品中藻毒素含量与两种qPCR方法得到的有毒藻数量之间并没有明显相关性。可见,基于产毒基因的检测方法在长江口邻近海域有毒藻类检测中具有一定优势,但不足以准确反映该海域藻毒素的水平。

The primary application of an sxtA-based qPCR assay to detect toxic algae in sea area adjacent to the Changjiang River Estuary

Paralytic shellfish toxins(PSTs), including saxitoxin(STX) and its analogues, are potent neurotoxins produced by toxic dinoflagellates and cyanobacteria. Studies recently revealed a set of genes for STX synthesis in toxic cyanobacteria and dinoflagellates, and methods have been developed to quantitatively detect some core genes specific for toxin synthesis. In this study, a qPCR assay targeted to STX-synthetic gene sxtA4 was applied to detect PST-producing algae in the sea area adjacent to the Changjiang River estuary, which is the most significant region for recurring harmful algal blooms in China.Samples of toxic algae and PSTs collected along two transects in spring 2013 were measured with this method in parallel with two Taqman-based qPCR assays for Group I and IV of Alexandrium tamarense species complex and a HPLC method for PST determination. It was found that abundance of sxtA gene has a close relationship with that of A. tamarense species complex Group IV(r2=0.52, P0.05), suggesting that toxic A. tamarense species complex(Group IV)is the major PST producer during the sampling season in this region. However, no apparent relationship was found between PST level and the abundance of toxic algae derived from those qPCR assays. In conclusion, the sxtA-based qPCR assay has its advantages in monitoring PST-producing toxic bloom in the Changjiang River estuary, but it's not accurate enough to reflect PST level in the sea.