Partitioning of Respiration in an Animal-Algal Symbiosis: Implications for Different Aerobic Capacity between Symbiodinium spp.
Partitioning of Respiration in an Animal-Algal Symbiosis: Implications for Different Aerobic Capacity between Symbiodinium spp.
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DOI：
10.3389/fphys.2016.00128
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发表时间：
2016
影响因子：
4
通讯作者：
Warner ME
中科院分区：
文献类型：
--
作者：
Hawkins TD;Hagemeyer JC;Hoadley KD;Marsh AG;Warner ME
刺胞动物 - 甲藻共生关系在生态学上具有重要意义，也是众多研究的主题。然而，我们对共生生理学的关键方面的理解，例如宿主和共生体之间总呼吸的分配，仍然不完整。具体而言，我们对不同的共生体（宿主 - 共生体组合）之间宿主和共生体呼吸的关系如何变化知之甚少。我们应用分子和生化技术研究了自然共生的海葵（Exaiptasia pallida）以及感染了同源的ITS2 - A4型共生甲藻（Symbiodinium）或异源的微小共生甲藻（Symbiodinium minutum，ITS2 - B1型）的动物的有氧呼吸能力。在自然共生的海葵中，宿主、共生体以及整个共生体的线粒体柠檬酸合酶（CS）酶活性，而非宿主线粒体拷贝数，是共生体呼吸的可靠预测指标。共生体密度与宿主CS比活性（每毫克蛋白质）呈正相关，宿主和共生体的CS比活性呈负相关。值得注意的是，在这个自然的苍白海葵（E. pallida）种群中，宿主和共生体之间总CS活性的分配与宿主/共生体生物量比值显著不同。在重新感染的海葵中，我们发现藻类共生体的CS比活性在不同共生体之间存在显著差异。此外，总CS活性的分配与宿主/共生体生物量比值之间的关系在不同共生体之间也有所不同。这些数据对我们理解刺胞动物 - 藻类共生关系具有广泛的影响。具体来说，长期以来认为共生体/宿主生物量和呼吸比相等的假设可能会导致对共生体呼吸的严重高估，并可能在关于转移到宿主的碳的百分比方面得出错误结论。共生体有氧能力的种间差异为不同的生理差异提供了进一步的证据，在研究不同的宿主 - 共生体组合时应考虑这些差异。
Cnidarian-dinoflagellate symbioses are ecologically important and the subject of much investigation. However, our understanding of critical aspects of symbiosis physiology, such as the partitioning of total respiration between the host and symbiont, remains incomplete. Specifically, we know little about how the relationship between host and symbiont respiration varies between different holobionts (host-symbiont combinations). We applied molecular and biochemical techniques to investigate aerobic respiratory capacity in naturally symbiotic Exaiptasia pallida sea anemones, alongside animals infected with either homologous ITS2-type A4 Symbiodinium or a heterologous isolate of Symbiodinium minutum (ITS2-type B1). In naturally symbiotic anemones, host, symbiont, and total holobiont mitochondrial citrate synthase (CS) enzyme activity, but not host mitochondrial copy number, were reliable predictors of holobiont respiration. There was a positive association between symbiont density and host CS specific activity (mg protein−1), and a negative correlation between host- and symbiont CS specific activities. Notably, partitioning of total CS activity between host and symbiont in this natural E. pallida population was significantly different to the host/symbiont biomass ratio. In re-infected anemones, we found significant between-holobiont differences in the CS specific activity of the algal symbionts. Furthermore, the relationship between the partitioning of total CS activity and the host/symbiont biomass ratio differed between holobionts. These data have broad implications for our understanding of cnidarian-algal symbiosis. Specifically, the long-held assumption of equivalency between symbiont/host biomass and respiration ratios can result in significant overestimation of symbiont respiration and potentially erroneous conclusions regarding the percentage of carbon translocated to the host. The interspecific variability in symbiont aerobic capacity provides further evidence for distinct physiological differences that should be accounted for when studying diverse host-symbiont combinations.