Abstract：
Diatom containing different active biological macromolecules are thought to be an excellent microbial cell factory. Phaeodactylum tricornutum, a model diatom, is a superb chassis organism accumulating chrysolaminarin with important bioactivities. However, the characteristic of chrysolaminarin accumulation and molecular mechanism of the fluctuated chrysolaminarin in diatom are still unknown. In this study, physiological data and transcriptomic analysis were carried out to clarify the mechanism involved in chrysolaminarin fluctuation. The results showed that chrysolaminarin content fluctuated, from 7.41 % dry weight (DW) to 40.01 % DW during one light/dark cycle, increase by day and decrease by night. The similar fluctuated characteristic was also observed in neutral lipid content. Genes related to the biosynthesis of chrysolaminarin and neutral lipid were up-regulated at the beginning of light-phase, explaining the accumulation of these biological macromolecules. Furthermore, genes involved in carbohydrate degradation, cell cycle, DNA replication and mitochondria-localized β-oxidation were up-regulated at the end of light phase and at the beginning of dark phase hinting an energy transition of carbohydrate to cell division during the dark period. Totally, our findings provide important information for the regulatory mechanism in the diurnal fluctuation of chrysolaminarin. It would also be of great help for the mass production of economical chrysolaminarin in marine diatom.
摘要：
含有不同活性生物大分子的硅藻被认为是优良的微生物细胞工厂。三角指藻，一个硅藻模型，是一种极好的底盘生物，具有重要的生物活性。然而,硅藻中大黄素的积累特征和波动大黄素的分子机制尚不清楚。在这项研究中,进行了生理数据和转录组学分析，以阐明大黄素波动的机制。结果表明,黄麻素含量波动较大,在一个亮/暗循环期间，从7.41%干重(DW)到40.01%DW，白天增加，晚上减少。在中性脂质含量中也观察到类似的波动特征。与大黄素和中性脂质生物合成相关的基因在光照期开始时上调，解释这些生物大分子的积累。此外，参与碳水化合物降解的基因，细胞周期,在光期结束时和暗期开始时，DNA复制和线粒体定位的β-氧化被上调，这暗示了碳水化合物在暗期向细胞分裂的能量转换。完全正确,我们的研究结果为大黄素的昼夜波动调节机制提供了重要信息。这也将对海洋硅藻中经济的大黄素的大规模生产有很大帮助。
