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 Ca²⁺-dependent signaling pathway, not previously described in eukaryotes, to sense and respond to the critical macronutrient P. We demonstrate that P-Ca²⁺ 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-Ca²⁺ signaling. P-Ca²⁺ 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.

硅藻是一个多样化且全球重要的浮游植物群，负责地球上约 20% 的碳固定。它们经常形成空间广泛的浮游植物大量繁殖，对包括磷 (P) 和氮 (N) 在内的养分供应的增加迅速做出反应。尽管众所周知，硅藻是水生生态系统中养分流入的常见第一反应者，但人们对它们用于养分感知的感官机制知之甚少。在这里，我们表明 P 限制硅藻使用 Ca ²⁺依赖的信号通路，以前没有在真核生物中描述过，来感知和响应关键的常量营养素 P。我们证明 P-Ca ²⁺信号在代表性的羽状结构之间是保守的（三角褐指藻) 和中心 ( Thalassiosira pseudonana ) 硅藻。此外，该途径与生态相关，对亚微摩尔浓度的无机磷酸盐和一系列环境丰富的 P 形式敏感。值得注意的是，我们表明硅藻从 P 限制中恢复需要快速和显着增加 N 同化，并证明该过程依赖于 P-Ca ²⁺信号传导。因此， P-Ca ²⁺信号控制了硅藻快速感知和响应 P 再供应的能力，调节重要营养素 P 和 N 之间的基本相互作用，并最大限度地提高脉冲养分供应区域的硅藻资源竞争。