Perception of environmental signal by a marine diatom

Diatoms are a key component of marine ecosystems and are extremely importan t for the biogeochemical cycling of silica and as contributors to global fi xed carbon. However, the answers to fundamental questions such as what diat oms can sense in their environment, how they respond to external signals, a nd what factors control their Life strategies are largely unknown. We gener ated transgenic diatom cells containing the calcium-sensitive photoprotein aequorin to determine whether changes in calcium homeostasis are used to re spond to relevant environmental stimuli. Our results reveal sensing systems for detecting and responding to fluid motion (shear stress), osmotic stres s, and iron, a key nutrient that controls diatom abundance in the ocean.