Ocean College, Zhejiang University, Zhoushan, 316021, China.
Ocean College, Zhejiang University, Zhoushan, 316021, China.
Harmful Algae. 2019 Nov;89:101672. doi: 10.1016/j.hal.2019.101672. Epub 2019 Oct 11.
The mixotrophic dinoflagellate Dinophysis acuminata is a widely distributed diarrhetic shellfish poisoning (DSP) producer. Toxin variability of Dinophysis spp. has been well studied, but little is known of the manner in which toxin production is regulated throughout the cell cycle in these species, in part due to their mixotrophic characteristics. Therefore, an experiment was conducted to investigate cell cycle regulation of growth, photosynthetic efficiency, and toxin production in D. acuminata. First, a three-step synchronization approach, termed "starvation-feeding-dark", was used to achieve a high degree of synchrony of Dinophysis cells by starving the cells for 2 weeks, feeding them once, and then placing them in darkness for 58 h. The synchronized cells started DNA synthesis (S phase) 10 h after being released into the light, initiated G2 growth stage eight hours later, and completed mitosis (M phase) 2 h before lights were turned on. The toxin content of three dominant toxins, okadaic acid (OA), dinophysistoxin-1 (DTX1) and pectenotoxin-2 (PTX2), followed a common pattern of increasing in G1 phase, decreasing on entry into the S phase, then increasing again in S phase and decreasing in M phase during the diel cell cycle. Specific toxin production rates were positive throughout the G1 and S phases, but negative during the transition from G1 to S phase and late in M phase, the latter reflecting cell division. All toxins were initially induced by the light and positively correlated with the percentage of cells in S phase, indicating that biosynthesis of Dinophysis toxins might be under circadian regulation and be most active during DNA synthesis.
混养型甲藻属中的拟菱形藻是一种广泛分布的腹泻性贝类毒素（DSP）产生者。对拟菱形藻属的毒素变异性进行了充分的研究，但对于这些物种在整个细胞周期中如何调节毒素产生的方式知之甚少，部分原因是它们具有混合营养的特性。因此，进行了一项实验以研究拟菱形藻属中细胞周期对生长、光合作用效率和毒素产生的调控。首先，采用三步同步法，称为“饥饿-喂养-黑暗”，通过让细胞饥饿 2 周、喂养一次，然后将其置于黑暗中 58 小时，实现了拟菱形藻细胞的高度同步。同步细胞在进入光照后 10 小时开始 DNA 合成（S 期），八小时后进入 G2 生长阶段，两小时前光照开启时完成有丝分裂（M 期）。三种主要毒素（OA、DTX1 和 PTX2）的毒素含量遵循一个共同的模式，即在 G1 期增加，进入 S 期后减少，然后在 S 期再次增加，在细胞昼夜周期的 M 期减少。特定毒素的产生率在整个 G1 和 S 期均为正值，但在从 G1 期到 S 期的过渡和 M 期后期为负值，后者反映细胞分裂。所有毒素最初都被光照诱导，并与 S 期细胞的百分比呈正相关，表明拟菱形藻毒素的生物合成可能受到昼夜节律的调节，在 DNA 合成期间最为活跃。
