硅藻对不同生态习性桡足类抗氧化相关基因表达的影响

Abstract

采用实时荧光定量PCR（qRT-PCR）技术比较3种不同生态习性的桡足类摄食不同浓度的2种硅藻牟氏角毛藻（Chaetoceros muelleri）和小新月菱形藻（Nitzschia closteriumf.minutissima）后,其2种抗氧化相关基因锰超氧化物歧化酶（MnSOD）和谷胱甘肽转移酶（GST）表达水平的变化情况.所用桡足类分别为哲水蚤类的太平洋纺锤水蚤（Acartia pacifica）、安氏伪镖水蚤（Pseudodiaptomus annandalei）和猛水蚤类的日本虎斑猛水蚤（Tigriopus japonicas）.结果显示:低浓度的硅藻对太平洋纺锤水蚤和安氏伪镖水蚤中MnSOD和GST基因的表达水平表现出显著的诱导效应,高浓度的硅藻则表现出抑制效应;而不论是低浓度还是高浓度的硅藻均能诱导日本虎斑猛水蚤中MnSOD和GST基因的表达.这表明不同类别的桡足类对硅藻的分子响应存在物种特异性.为评估哲水蚤桡足类对硅藻的影响是否具有适应能力,进而将哲水蚤类的安氏伪镖水蚤在摄食上述2种硅藻条件下连续培养4个世代,并对其每个世代中MnSOD基因的表达水平进行分析.结果显示:牟氏角毛藻饲喂的安氏伪镖水蚤中,第4个世代的MnSOD基因表达水平显著高于第1个世代;而小新月菱形藻饲喂的安氏伪镖水蚤中,后3个世代的MnSOD基因表达水平均显著高于第1个世代.由此推测安氏伪镖水蚤可以对2种硅藻产生遗传适应,并且适应机制可能不同.Expressions of two antioxidant genes, <i>MnSOD</i> and <i>GST</i>,were determined by real-time quantitative PCR(qRT-PCR)in three species of copepods with different ecological habits,when feeding on two diatoms of <i>Chaetoceros muelleri</i> and <i>Nitzschia closterium</i> f.<i>minutissima</i> at different concentrations.The copepods used in this study were pelagic calanoid copepods of <i>Acartia pacifica</i> and <i>Pseudodiaptomus annandalei</i> and benthic hapacticoid copepod of <i>Tigriopus japonicas</i>.The results showed that gene expressions were induced significantly in <i>A.pacifica</i> and <i>P.annandalei</i> feeding on two diatoms at lower concentrations,while restrained at higher concentrations,whereas <i>MnSOD</i> and <i>GST</i> gene expressions were induced in <i>T.japonicas</i> feeding on diatoms at both lower and higher concentrations.The results suggested that gene expression response of copepods to diatoms were species-specific.To evaluate whether calanoid copepod had the capacity to be acclimatized to diatoms,<i>P.annandalei</i> was cultured for four generations feeding on the two diatoms and the <i>MnSOD</i> gene expression was determined for each generation.It was shown that the <i>MnSOD</i> gene expression level of the forth generation was significantly higher than the first generation when fed on <i>C.muelleri</i>,however,when fed on <i>N.closterium</i> f.<i>minutissima</i>,the <i>MnSOD</i> gene expression levels of the latter three generations were all significantly higher than the first generation,demonstrating that <i>P.annandalei</i> might have adapted to the two diatoms with different mechanisms.