Aquatic Animal Medicine, Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, S-110 Plant Biology Building, East Lansing, MI 48824, USA.
Mol Genet Genomics. 2010 Apr;283(4):327-39. doi: 10.1007/s00438-010-0517-8. Epub 2010 Feb 11.
Since its invasion to the North American waters 20 years ago, the zebra mussel (Dreissena polymorpha) has negatively impacted the ecosystems through its firm underwater adhesion. The molecular mechanisms governing the functions of the zebra mussel byssus, the main structure responsible for maintaining the underwater adhesion, have received little attention. Our previously developed zebra mussel foot byssus cDNA microarray was applied in this study to identify the genes involved in different stages of the byssal threads generation. Byssal threads of zebra mussels were manually severed under laboratory conditions and the formation of new byssal threads was followed over a 3 week course. By comparing the gene expression profiles in different stages of byssal threads generation (byssogenesis) to their baseline values, we found that the number of unique byssus genes differentially expressed at 12-h, 1, 2, 3, 4, 7, and 21 days post-treatment was 13, 13, 20, 17, 16, 20, and 29, respectively. Comparisons were also made between two subsequent samples (e.g., 12 h vs. 1, 1 vs. 2 days, 2 vs. 3 days, and so on). Seven differentially expressed genes were selected for validation by using quantitative reverse transcription PCR (qRT-PCR) and the results were consistent with those from the microarray analysis. By using fluorescent in situ hybridization, we found that two microarray identified genes, BG15_F03-DPFP and BG16_H05-EGP, were expressed in two major byssus glands located in the zebra mussel foot: the stem-forming gland and plaque-forming gland, respectively. Moreover, the qRT-PCR of seven microarray identified genes with different zebra mussel samples suggested that they were also expressed in other mussel tissues beside the foot, albeit at much lower levels. This suggested that the microarray identified genes were produced primarily by the foot, and were likely associated with byssogenesis. The differentially expressed genes identified in this study indicated that multiple molecules are involved in byssogenesis, most likely performing multiple functions during the generation of byssal threads. These results obtained herein represent the first logical step toward understanding underwater attachment mechanisms employed by this invasive species.
自 20 年前入侵北美水域以来，斑马贻贝（Dreissena polymorpha）通过其牢固的水下附着力对生态系统造成了负面影响。负责维持水下附着力的主要结构——贻贝足丝的功能所涉及的分子机制还没有得到太多关注。我们之前开发的斑马贻贝足丝 cDNA 微阵列被应用于本研究，以鉴定参与不同阶段足丝生成的相关基因。在实验室条件下手动切断斑马贻贝的足丝，然后在接下来的 3 周内跟踪新足丝的生成。通过比较不同阶段足丝生成（足丝发生）过程中的基因表达谱与其基线值，我们发现，在处理后 12 小时、1 天、2 天、3 天、4 天、7 天和 21 天，有 13、13、20、17、16、20 和 29 个独特的足丝基因差异表达。我们还对两个连续的样本进行了比较（例如，12 小时与 1 天、1 天与 2 天、2 天与 3 天等）。选择了 7 个差异表达基因进行定量逆转录 PCR（qRT-PCR）验证，结果与微阵列分析一致。通过荧光原位杂交，我们发现，在两个主要的位于斑马贻贝足部的足丝腺中——生柄腺和生板腺，两个在微阵列中鉴定出的基因 BG15_F03-DPFP 和 BG16_H05-EGP 均有表达。此外，对来自不同斑马贻贝样本的 7 个微阵列鉴定基因的 qRT-PCR 表明，它们也在足部以外的其他贻贝组织中表达，尽管表达水平较低。这表明，微阵列鉴定的基因主要由足部产生，可能与足丝发生有关。本研究中鉴定的差异表达基因表明，多个分子参与了足丝发生，很可能在足丝生成过程中发挥了多种功能。这些结果代表了理解这种入侵物种水下附着机制的第一个逻辑步骤。
