BRC-BIO: Evolutionary Patterns of Ice-Binding Proteins in North Pacific Intertidal Invertebrates

Animals living in polar regions must survive freezing conditions for several months of the year. Freezing water, specifically ice crystals, can damage soft tissues and kill organisms that are not adapted to freezing conditions. Several species – from fish to beetles to bacteria – have developed physiological mechanisms to withstand freezing conditions, most notably by producing proteins that bind to ice, some of which are called ‘antifreeze’ proteins.

Just as antifreeze solution in a car lowers the freezing point of water, antifreeze proteins protect organisms’ tissues from damaging ice crystals. Little is known about these proteins in marine invertebrates such as sea stars, which are important predators in intertidal habitats. Recent genetic evidence suggests sea stars may produce new forms of these proteins.

This study will investigate the genetic mechanisms behind intertidal sea stars’ ability to produce proteins to survive in sub-freezing water in Alaska and how protein production varies by season and temperature. Understanding the function of these proteins and the environmental conditions that trigger their production will allow researchers to make predictions on how sea stars will adapt to extreme climatic events.

The results from this work may aid the growing mariculture industry for invertebrates such as sea cucumbers and urchins, which are close relatives of sea stars. Furthermore, if sea stars produce novel proteins, their discovery may lead to innovations in biomedical cryopreservation and commercial agriculture. This project will create opportunities for undergraduates, particularly Alaska Natives, to learn professional skills in STEM through mentoring, research, workshops and professional development.

Intertidal invertebrates in polar regions overcome unique environmental challenges compared to their pelagic (open water) and benthic (deep sea) counterparts, including large daily winter temperature fluctuations. Freezing conditions can lead to lethal cellular damage through the formation of ice crystals on soft tissues. Many cold-adapted ectothermic organisms have evolved mechanisms to prevent damage from cold by producing ice-binding proteins (IBPs).

IBPs bind to ice crystal planes and have a variety of functions, from ice recrystallization and growth inhibition (antifreeze) to the controlled formation (nucleation) of ice. Recent evidence offers potential for discovering novel IBPs in marine invertebrates. The objective of this project is to describe the extent to which IBP production exists and is environmentally correlated across select lineages of intertidal invertebrates that primarily inhabit the Arctic and subarctic.

The project will combine freezing assays with genome and transcriptome sequencing to characterize the evolution of IBPs in several lineages of intertidal invertebrates to determine ice-binding activity in one clade of intertidal invertebrates (Echinodermata) inhabiting the North Pacific, identify the class of IBPs and functional gene regions in two lineages of echinoderm sea stars predicted to exhibit ice-binding activity and cold tolerance, and quantify IBP production (gene expression) in sea stars across seasons and temperature gradients. The research will address a major gap in the field of cold-water adaptation by quantifying ice-binding activity in dozens of intertidal species.

This project is jointly funded by the Directorate for the Biological Sciences and the Established Program to Stimulate Competitive Research (EPSCoR).

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.