Investigating the utilization and production of iron siderophores by marine dinoflagellates

Dinoflagellates are single-celled marine organisms that play critical roles in ocean ecosystems. They support coral reefs as symbionts, contribute to food webs, and can also form harmful algal blooms (“red tides”) that release toxins affecting marine life and human health. Despite their importance, the factors that regulate their growth and bloom formation remain poorly understood. This project investigates how dinoflagellates acquire iron, an essential but scarce nutrient in seawater. It focuses on siderophores, specialized molecules that bind and transport iron, and tests whether dinoflagellates can produce and utilize these compounds to gain a competitive advantage. The project integrates laboratory experiments, microscopy and genomic analyses to identify uptake mechanisms and the genes involved. This work will improve understanding of nutrient cycling and bloom dynamics in marine systems, while training students, integrating research into coursework, and engaging the public through community-based environmental monitoring. Siderophores are low molecular weight compounds produced by fungi and bacteria that exhibit high affinity for ferric iron, thereby maintaining iron in solution and enhancing its bioavailability in marine systems. Emerging evidence suggests that dinoflagellates may also produce siderophores and acquire Fe-siderophore complexes, potentially via TonB-dependent transporters (TBDTs), yet the prevalence and mechanisms of the process remain poorly understood. This project investigates siderophore utilization and production across cultured strains of photosynthetic marine dinoflagellates and characterizes the mechanisms of siderophore uptake in Amphidinium carterae. The investigators will (i) quantify Fe-siderophore uptake kinetics, (ii) visualize uptake and assimilation using fluorescent siderophore conjugates, (iii) analyze existing genomic and transcriptomic datasets to identify TBDT analogs and other candidate genes implicated in siderophore transport, (iv) conduct comparative transcriptomic analyses under iron-replete vs. siderophore-supplemented condition to asses differential gene expression, and (v) functionally test candidate genes using RNA silencing approaches to determine their role in siderophore-mediated iron acquisition. By integrating physiological experiments with molecular and bioinformatic analyses, this project resolves the mechanistic basis and ecological relevance of siderophore use in dinoflagellates. This provides new insights into iron cycling and nutrient limitation in marine ecosystems and improve understanding of the processes that contribute to dinoflagellate success, including their roles in coral symbioses and harmful algal blooms. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2546889 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Julie Granger | Institution: University of Connecticut, STORRS, CT | Award Amount: $867,033 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2546889 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2546889.html