Transcriptional response of the marine pennate diatom Phaeodactylum tricornutum to Fe limitation. Phaeodactylum tricornutum

Diatoms, which are responsible for up to 40% of the 45 to 50 billion metric tons of organic carbon production each year in the sea, are particularly sensitive to Fe stress. Here we describe the transcriptional response of the pennate diatom Phaeodactylum tricornutum to Fe limitation using a partial genome microarray based on EST and genome sequence data. Processes carried out by components rich in Fe, such as photosynthesis, mitochondrial electron transport and nitrate assimilation are down-regulated to cope with the reduced cellular iron quota. This retrenchment is compensated by nitrogen (N) and carbon (C) reallocation from protein and storage carbohydrate degradation, adaptations to chlorophyll biosynthesis and pigment metabolism, removal of excess electron s by mitochondrial alternative oxidase (AOX), augmented Fe-independent oxidative stress responses, and sensitized iron capture mechanisms. Keywords: Marine phytoplankton, pinnate diatom Overall design: Wild-type Phaeodactylum tricornutum was grown under Fe replete (10,000 nM) and Fe limiting (5nM) conditions. Partial genome gene expression analysis of iron-inducible genes was conducted using a two-color competitive hybridization microarray.

硅藻每年在全球海洋有机碳总产量（450~500亿吨）中可贡献高达40%的份额，且对铁胁迫尤为敏感。本研究依托表达序列标签（Expressed Sequence Tag, EST）与基因组序列数据构建的部分基因组微阵列，解析了羽纹硅藻三角褐指藻（Phaeodactylum tricornutum）在铁限制条件下的转录响应。富铁蛋白组分参与的核心生理过程，如光合作用、线粒体电子传递与硝酸盐同化，均被下调以适配细胞内铁储量的缩减。这种代谢层面的缩减可通过多种途径实现补偿：从蛋白质与贮藏性碳水化合物的降解过程中重新分配氮（N）与碳（C）、调控叶绿素生物合成与色素代谢通路、通过线粒体交替氧化酶（Alternative Oxidase, AOX）清除过量电子、增强不依赖铁的氧化应激响应，以及强化铁捕获机制。关键词：海洋浮游植物，羽纹硅藻。实验设计：野生型三角褐指藻分别在铁充足（10,000 nM）与铁限制（5 nM）的培养条件下生长。本研究采用双色竞争性杂交微阵列，开展了铁诱导基因的部分基因组基因表达分析。