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    低温胁迫对大黄鱼mettl3mettl14表达及RNA m6A修饰的影响

    Low-Temperature Stress on the Expression of mettl3 and mettl14 and RNA m6A Modification in Larimichthys crocea

    • 摘要: 本研究以大黄鱼(Larimichthys crocea)为研究对象, 分析低温胁迫下N6-甲基腺苷(m6A)甲基化水平及甲基转移酶Lc-mettl3Lc-mettl14的表达特征, 并探讨其与MAPK信号通路的潜在关联。扩增获得Lc-METTL3和Lc-METTL14的cDNA核心编码序列并进行生物信息学分析。采用实时荧光定量PCR技术(RT-qPCR)检测其组织表达分布及在不同温度和低温(8℃)胁迫时间梯度下的表达变化, 结合Western blot分析Lc-METTL14蛋白表达水平, 并检测肝脏整体m6A甲基化水平变化。基于MeRIP-seq数据筛选差异m6A甲基化基因并进行KEGG富集分析, 结合RT-qPCR验证MAPK信号通路相关基因表达变化。Lc-mettl3Lc-mettl14基因在大黄鱼多种组织中均有表达, 其中在肝脏中表达水平较高。在低温胁迫条件下, Lc-mettl3Lc-mettl14基因在肝脏中的表达随温度降低及胁迫时间延长呈下降趋势, 且Lc-METTL14蛋白表达变化与其转录水平一致。肝脏整体m6A甲基化水平在低温胁迫下显著降低, 并呈时间依赖性变化。MeRIP-seq分析鉴定到大量m6A甲基化受低温影响的基因, 这些基因显著富集于MAPK等信号通路及代谢相关通路。进一步分析发现, map2k7、map3k14a、 map4k4mapk8b四个MAPK通路相关基因在低温胁迫下表现出m6A修饰水平升高, 并呈现基因特异性的转录响应模式。在低温胁迫下, 肝脏中基因的m6A甲基化水平与Lc-mettl3Lc-mettl14基因表达均呈下降趋势, 并伴随MAPK信号通路相关基因m6A修饰及表达的动态变化。结果表明, m6A介导的转录后调控可能参与大黄鱼低温胁迫过程中MAPK信号通路的调控。本研究为鱼类低温胁迫响应的表观遗传调控机制提供了新的理论依据。

       

      Abstract: N6-methyladenosine (m6A), a predominant epigenetic modification of RNA in eukaryotes, exerts crucial regulatory functions during environmental adaptation. Nevertheless, the responsive profiles and functional mechanisms of m6A under cold stress remain poorly understood in teleost fish. In the present study, large yellow croaker (Larimichthys crocea) was selected as the experimental organism to characterize the alterations in global m6A methylation levels, together with the expression patterns of two methyltransferases Lc-mettl3 and Lc-mettl14 under cold stress, and to further explore their potential correlation with the mitogen-activated protein kinase (MAPK) signaling pathway. The core coding sequences (CDS) of Lc-METTL3 and Lc-METTL14 were cloned and subjected to comprehensive bioinformatic analyses. Real-time quantitative PCR (RT-qPCR) was applied to detect the tissue expression profiles as well as the transcriptional dynamics of the two genes under gradient temperatures and 8℃ cold stress with different exposure durations. Western blot was performed to quantify the protein abundance of Lc-METTL14, and the total hepatic m6A methylation level was biochemically measured. Differentially m6A-methylated genes were screened based on MeRIP-seq data, followed by KEGG pathway enrichment analysis. RT-qPCR was used to verify the transcriptional changes of hub genes within the MAPK signaling cascade. Both Lc-mettl3 and Lc-mettl14 were ubiquitously expressed in examined tissues of L. crocea, with the highest transcript abundance detected in the liver. Under cold stress, the hepatic mRNA levels of Lc-mettl3 and Lc-mettl14 declined gradually with the decrease in ambient temperature and the prolongation of cold exposure; the protein expression trend of Lc-METTL14 was consistent with its transcriptional variation. Global hepatic m6A methylation was significantly reduced upon cold treatment in a time-dependent manner. A large set of genes with altered m6A modification were identified via MeRIP-seq, which were significantly enriched in the MAPK signaling pathway and multiple metabolism-associated pathways. Four MAPK pathway genes (map2k7, map3k14a, map4k4, mapk8b) exhibited elevated m6A modification levels after cold stress, accompanied by gene-specific transcriptional responsive patterns. Cold stress repressed the expression of hepatic Lc-mettl3/Lc-mettl14 and decreased the global m6A methylation level in the liver, along with dynamic shifts in m6A modification and transcription of MAPK pathway genes. Collectively, our findings suggest that m6A-dependent post-transcriptional regulation participates in modulating the MAPK signaling pathway during cold stress response in L. crocea. This study provides novel theoretical insights into the epigenetic regulatory mechanism underlying cold acclimation in marine fish species.

       

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