Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Mathematics & Statistics, Dalhousie University, Halifax, Nova Scotia, Canada.
PLoS One. 2023 Jan 24;18(1):e0280827. doi: 10.1371/journal.pone.0280827. eCollection 2023.
In large areas of the ocean, iron concentrations are insufficient to promote phytoplankton growth. Numerous studies have been conducted to characterize the effect of iron on algae and how algae cope with fluctuating iron concentrations. Fertilization experiments in low-iron areas resulted primarily in diatom-dominated algal blooms, leading to laboratory studies on diatoms comparing low- and high-iron conditions. Here, we focus on the short-term temporal response following iron addition to an iron-starved open ocean diatom, Thalassiosira oceanica. We employed the NanoString platform and analyzed a high-resolution time series on 54 transcripts encoding proteins involved in photosynthesis, N-linked glycosylation, iron transport, as well as transcription factors. Nine transcripts were iron-responsive, with an immediate response to the addition of iron. The fastest response observed was the decrease in transcript levels of proteins involved in iron uptake, followed by an increase in transcript levels of iron-containing enzymes and a simultaneous decrease in the transcript levels of their iron-free replacement enzymes. The transcription inhibitor actinomycin D was used to understand the underlying mechanisms of the decrease of the iron-responsive transcripts and to determine their half-lives. Here, Mn-superoxide dismutase (Mn-SOD), plastocyanin (PETE), ferredoxin (PETF) and cellular repressor of EA1-stimulated genes (CREGx2) revealed longer than average half-lives. Four iron-responsive transcripts showed statistically significant differences in their decay rates between the iron-recovery samples and the actD treatment. These differences suggest regulatory mechanisms influencing gene transcription and mRNA stability. Overall, our study contributes towards a detailed understanding of diatom cell biology in the context of iron fertilization response and provides important observations to assess oceanic diatom responses following sudden changes in iron concentrations.
在海洋的大部分区域，铁浓度不足以促进浮游植物的生长。大量研究已经对铁对藻类的影响以及藻类如何应对铁浓度的波动进行了描述。在缺铁区域进行的施肥实验主要导致了以硅藻为主的藻类大量繁殖，这导致了在实验室条件下对硅藻进行的比较低铁和高铁条件的研究。在这里，我们关注的是在缺铁的开阔海域硅藻 Thalassiosira oceanica 中添加铁后短期的时间响应。我们采用了 NanoString 平台，并对 54 个编码与光合作用、N 连接糖基化、铁转运以及转录因子相关的蛋白的转录本进行了高分辨率的时间序列分析。有 9 个转录本对铁有反应，对铁的添加有立即的响应。观察到的最快响应是铁摄取蛋白的转录本水平下降，随后含铁酶的转录本水平增加，同时其无铁替代酶的转录本水平下降。转录抑制剂放线菌酮 D 被用于理解铁响应转录本减少的潜在机制，并确定它们的半衰期。这里，锰超氧化物歧化酶 (Mn-SOD)、质体蓝素 (PETE)、铁氧还蛋白 (PETF) 和 EA1 刺激基因的细胞阻遏物 (CREGx2) 显示出比平均半衰期更长的半衰期。有 4 个铁响应转录本在铁恢复样本和 actD 处理之间的衰减率有统计学上的显著差异。这些差异表明存在影响基因转录和 mRNA 稳定性的调控机制。总的来说，我们的研究有助于在铁施肥响应的背景下深入了解硅藻的细胞生物学，并提供了重要的观察结果来评估海洋硅藻对铁浓度突然变化的反应。
