School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
Key Laboratory of Tropical Marine Bio-resources and Ecology (LMB), South China Sea Institute of Oceanology, Chinese Academy of Sciences, China.
FEMS Microbiol Ecol. 2019 Nov 1;95(11). doi: 10.1093/femsec/fiz150.
This study examines the physiological responses of the Symbiodiniumvoratum (clade E) to two types of phosphates having different chemical bonds-phosphoesters (C-O-P bonds) and phosphonates (C-P bonds) to explore Symbiodinium cell growth and the molecular perspective of the P utilization process. Alkaline phosphatase (AP), PhnX, PhoA and PhoX expression was profiled for different P conditions using the RT-qPCR method. In a sterile system, Symbiodinium could decompose phosphoesters, such as ATP and glucose 6-phosphate (G-6-P), into dissolved inorganic P (DIP) to supplement inorganic phosphorus but could not directly use phosphoesters for growth. The growth rate and photosynthetic efficiency of zooxanthellae in phosphoester-containing media did not significantly differ from those in the DIP group but were significantly inhibited in medium containing phosphonates such as N-(phosphonomethyl)glycine (glyphosate) and 2-aminoethylphosphonic acid (2-AEP), as well as in DIP-poor medium. The phosphonate group DIP concentration did not change remarkably, indicating that phosphonates can neither be directly used by zooxanthellae nor decomposed into DIP. Our RT-qPCR results support our views that the phosphoesters (C-O-P) had been hydrolyzed outside the cell before being absorbed into the Symbiodinium cell, and implies that PhnX, PhoA and PhoX are perhaps responsible for transporting DIP from medium into cells and for storage of DIP.
本研究考察了 Symbiodiniumvoratum（E 类群）对两种具有不同化学键的磷酸盐（磷酸酯（C-O-P 键）和膦酸盐（C-P 键））的生理反应，以探索 Symbiodinium 细胞生长和 P 利用过程的分子视角。使用 RT-qPCR 方法对不同 P 条件下的碱性磷酸酶 (AP)、PhnX、PhoA 和 PhoX 表达进行了分析。在无菌系统中，Symbiodinium 可以将磷酸酯（如 ATP 和葡萄糖 6-磷酸（G-6-P））分解为溶解无机磷（DIP）来补充无机磷，但不能直接利用磷酸酯进行生长。含磷酸酯培养基中虫黄藻的生长速度和光合效率与 DIP 组没有显著差异，但在含有膦酸盐（如 N-（膦酸甲基）甘氨酸（草甘膦）和 2-氨基乙基膦酸（2-AEP））以及 DIP 贫化培养基中则受到显著抑制。磷酸酯基团 DIP 浓度没有明显变化，表明磷酸酯不能被虫黄藻直接利用，也不能分解成 DIP。我们的 RT-qPCR 结果支持我们的观点，即磷酸酯（C-O-P）在被 Symbiodinium 细胞吸收之前已经在细胞外被水解，并且暗示 PhnX、PhoA 和 PhoX 可能负责将 DIP 从培养基中运入细胞并储存 DIP。
