Climate Change Cluster, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
Division of Plant Science, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.
Photosynth Res. 2018 May;136(2):147-160. doi: 10.1007/s11120-017-0452-1. Epub 2017 Oct 4.
Seagrasses are a diverse group of angiosperms that evolved to live in shallow coastal waters, an environment regularly subjected to changes in oxygen, carbon dioxide and irradiance. Zostera muelleri is the dominant species in south-eastern Australia, and is critical for healthy coastal ecosystems. Despite its ecological importance, little is known about the pathways of carbon fixation in Z. muelleri and their regulation in response to environmental changes. In this study, the response of Z. muelleri exposed to control and very low oxygen conditions was investigated by using (i) oxygen microsensors combined with a custom-made flow chamber to measure changes in photosynthesis and respiration, and (ii) reverse transcription quantitative real-time PCR to measure changes in expression levels of key genes involved in C metabolism. We found that very low levels of oxygen (i) altered the photophysiology of Z. muelleri, a characteristic of C mechanism of carbon assimilation, and (ii) decreased the expression levels of phosphoenolpyruvate carboxylase and carbonic anhydrase. These molecular-physiological results suggest that regulation of the photophysiology of Z. muelleri might involve a close integration between the C and C, or other CO concentrating mechanisms metabolic pathways. Overall, this study highlights that the photophysiological response of Z. muelleri to changing oxygen in water is capable of rapid acclimation and the dynamic modulation of pathways should be considered when assessing seagrass primary production.
海草是一组多样化的被子植物，它们进化到生活在浅海水域，这是一个经常受到氧气、二氧化碳和光照变化的环境。巨藻是澳大利亚东南部的优势物种，对健康的沿海生态系统至关重要。尽管它具有重要的生态意义，但人们对巨藻中碳固定的途径及其对环境变化的调节机制知之甚少。在这项研究中，使用（i）氧微传感器与定制的流动室相结合来测量光合作用和呼吸作用的变化，以及（ii）逆转录定量实时 PCR 来测量参与 C 代谢的关键基因表达水平的变化，研究了暴露于对照和极低氧条件下的巨藻的反应。我们发现，极低水平的氧气（i）改变了巨藻的光生理学，这是 C 同化机制的特征，以及（ii）降低了磷酸烯醇丙酮酸羧化酶和碳酸酐酶的表达水平。这些分子生理学结果表明，巨藻光生理学的调节可能涉及 C 和 C 之间的紧密整合，或其他 CO 浓缩机制代谢途径。总的来说，这项研究强调了巨藻对水中氧气变化的光生理反应能够快速适应，在评估海草初级生产力时，应该考虑途径的动态调节。
