Redox signaling in colonial hydroids: many pathways for peroxide

Area of Science:

• Marine Biology
• Cellular Signaling
• Redox Biology

Background:

• Colonial hydroids Eirene viridula and Podocoryna carnea exhibit distinct growth forms ('sheet-like' vs. 'runner-like').
• Mitochondrial redox signaling suggests these hydroids should respond to reactive oxygen species (ROS) manipulations.

Purpose of the Study:

• To investigate the role of reactive oxygen species (ROS) in the growth and development of Eirene viridula and Podocoryna carnea.
• To explore how ROS signaling impacts colonial morphology and tissue survival in these hydroid species.

Main Methods:

• Treatment of hydroid colonies with the antioxidant vitamin C to alter ROS levels.
• Application of exogenous catalase and hydrogen peroxide to modulate ROS.
• Microscopic observation and measurement of ROS levels in different tissues (epitheliomuscular cells, stolon tips).

Main Results:

• Vitamin C diminished ROS in mitochondrion-rich cells, inducing 'sheet-like' growth, but increased ROS in stolon tips, causing tissue death.
• Exogenous catalase increased ROS in stolon tips, promoting 'runner-like' growth, while hydrogen peroxide also enhanced stolon tip ROS and growth.
• E. viridula exhibited higher basal ROS levels in stolon tips compared to P. carnea.

Conclusions:

• ROS plays a multifaceted role in hydroid colony development, influencing growth, tissue death, and potentially inter-colony interactions.
• ROS signaling in stolon tips may regulate outward growth, inhibit branching, and mediate redox signaling in epitheliomuscular cells.
• ROS might function extracellularly to inhibit bacterial growth, suggesting an ecological role for redox signaling.