Centre Scientifique de Monaco, Monaco, Monaco.
PLoS One. 2013;8(3):e58652. doi: 10.1371/journal.pone.0058652. Epub 2013 Mar 27.
Since the preindustrial era, the average surface ocean pH has declined by 0.1 pH units and is predicted to decline by an additional 0.3 units by the year 2100. Although subtle, this decreasing pH has profound effects on the seawater saturation state of carbonate minerals and is thus predicted to impact on calcifying organisms. Among these are the scleractinian corals, which are the main builders of tropical coral reefs. Several recent studies have evaluated the physiological impact of low pH, particularly in relation to coral growth and calcification. However, very few studies have focused on the impact of low pH at the global molecular level. In this context we investigated global transcriptomic modifications in a scleractinian coral (Pocillopora damicornis) exposed to pH 7.4 compared to pH 8.1 during a 3-week period. The RNAseq approach shows that 16% of our transcriptome was affected by the treatment with 6% of upregulations and 10% of downregulations. A more detailed analysis suggests that the downregulations are less coordinated than the upregulations and allowed the identification of several biological functions of interest. In order to better understand the links between these functions and the pH, transcript abundance of 48 candidate genes was quantified by q-RT-PCR (corals exposed at pH 7.2 and 7.8 for 3 weeks). The combined results of these two approaches suggest that pH≥7.4 induces an upregulation of genes coding for proteins involved in calcium and carbonate transport, conversion of CO2 into HCO3(-) and organic matrix that may sustain calcification. Concomitantly, genes coding for heterotrophic and autotrophic related proteins are upregulated. This can reflect that low pH may increase the coral energy requirements, leading to an increase of energetic metabolism with the mobilization of energy reserves. In addition, the uncoordinated downregulations measured can reflect a general trade-off mechanism that may enable energy reallocation.
自工业化前时代以来，海水表层平均 pH 值已下降了 0.1 个单位，并预计到 2100 年将再下降 0.3 个单位。尽管这种下降幅度很小，但对碳酸盐矿物的海水饱和状态有深远的影响，因此预计会对钙化生物产生影响。其中包括造礁石珊瑚，它们是热带珊瑚礁的主要建造者。最近有几项研究评估了低 pH 值对珊瑚生理的影响，特别是与珊瑚生长和钙化有关的影响。然而，很少有研究关注低 pH 值对全球分子水平的影响。在这种情况下，我们研究了在 3 周的时间内将石珊瑚（Pocillopora damicornis）暴露于 pH7.4 与 pH8.1 条件下的全球转录组修饰。RNAseq 方法表明，我们的转录组中有 16%受到了处理的影响，其中上调了 6%，下调了 10%。更详细的分析表明，下调的调控不如上调的调控协调，并且可以鉴定出一些感兴趣的生物学功能。为了更好地理解这些功能与 pH 值之间的联系，我们通过 q-RT-PCR 对 48 个候选基因的转录丰度进行了定量（在 pH7.2 和 pH7.8 下暴露 3 周的珊瑚）。这两种方法的综合结果表明，pH≥7.4 会诱导参与钙和碳酸盐转运、将 CO2 转化为 HCO3(-)和有机基质的基因的上调，这可能维持钙化作用。同时，异养和自养相关蛋白的编码基因也上调。这可能反映了低 pH 值可能会增加珊瑚的能量需求，导致能量代谢增加，并利用能量储备。此外，测量到的未协调下调可能反映了一种通用的权衡机制，这种机制可能使能量重新分配。
