Marine Biological Association, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK; Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK.
Marine Biological Association, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK.
Curr Biol. 2021 Mar 8;31(5):978-989.e4. doi: 10.1016/j.cub.2020.11.073. Epub 2020 Dec 28.
Diatoms are a diverse and globally important phytoplankton group, responsible for an estimated 20% of carbon fixation on Earth. They frequently form spatially extensive phytoplankton blooms, responding rapidly to increased availability of nutrients, including phosphorus (P) and nitrogen (N). Although it is well established that diatoms are common first responders to nutrient influxes in aquatic ecosystems, little is known of the sensory mechanisms that they employ for nutrient perception. Here, we show that P-limited diatoms use a Ca-dependent signaling pathway, not previously described in eukaryotes, to sense and respond to the critical macronutrient P. We demonstrate that P-Ca signaling is conserved between a representative pennate (Phaeodactylum tricornutum) and centric (Thalassiosira pseudonana) diatom. Moreover, this pathway is ecologically relevant, being sensitive to sub-micromolar concentrations of inorganic phosphate and a range of environmentally abundant P forms. Notably, we show that diatom recovery from P limitation requires rapid and substantial increases in N assimilation and demonstrate that this process is dependent on P-Ca signaling. P-Ca signaling thus governs the capacity of diatoms to rapidly sense and respond to P resupply, mediating fundamental cross-talk between the vital nutrients P and N and maximizing diatom resource competition in regions of pulsed nutrient supply.
硅藻是一个多样且具有全球重要意义的浮游植物群体，估计地球上有 20%的碳固定是由它们完成的。它们经常形成空间上广泛分布的浮游植物水华，对营养物质（包括磷（P）和氮（N））的增加迅速做出反应。虽然人们已经清楚地认识到，硅藻是水生生态系统中对营养物质流入的常见首批响应者，但对于它们用于营养感知的感应机制却知之甚少。在这里，我们表明，受磷限制的硅藻使用一种以前在真核生物中未描述过的 Ca 依赖性信号通路来感知和响应关键的大量营养素 P。我们证明，P-Ca 信号在代表性的羽纹硅藻（Phaeodactylum tricornutum）和中心硅藻（Thalassiosira pseudonana）之间是保守的。此外，这条途径在生态上是相关的，对亚微米级浓度的无机磷酸盐和一系列环境中丰富的 P 形态敏感。值得注意的是，我们表明，硅藻从磷限制中恢复需要迅速和大量增加氮同化，并且证明这个过程依赖于 P-Ca 信号。因此，P-Ca 信号控制了硅藻快速感知和响应磷供应的能力，介导了磷和氮这两种重要营养物质之间的基本交叉对话，并使硅藻在脉冲营养供应的区域中最大限度地提高了资源竞争能力。
