Project – Coral Cell Biology and Physiology

Funded by NSF EF-1220641

coral pic IG_GK

Measuring oxygen near coral polyps through a microelectrode (top left). Credit: Lauren Linsmayer

We are studying basic molecular and cellular mechanisms in corals, with the ultimate goal of understanding their importance in normal coral biology and in mediating responses to metabolic and environmental stress. Some specific projects and papers include:

1) “High adenylyl cyclase activity and diel cAMP fluctuations in corals suggest central physiological role”(1) demonstrated an unusually high capacity for cAMP production in coral extracts, as well as diurnal variations in cAMP content, with higher cAMP levels during the day compared to the night. This paper also reports stimulation of cAMP production by bicarbonate and sensitivity to KH7, a specific inhibitor of soluble adenylyl cyclase (sAC). We also found that forskolin, a typical stimulator of transmembrane adenyly cyclases (tmAC), does not have any effect on cAMP production in Pocillopora damicornis. The next step is to identify the physiological significance of the cAMp pathway in corals, which is a virtually unexplored, and potentially significant, topic in coral biology. Potential roles include regulation of coral growth, calcification, photosynthesis, and metabolism.
(1) Barott KL, Helman Y, Haramaty L, Barron ME, Hess KC, Buck J, Levin LR, Tresguerres M (2013) Sci Rep. 3:1379 (7 pgs).

2) “Symbiosome acidification by host proton pump promotes photosynthesis in corals” (2) describes a novel carbon concentrating mechanism in coral host cells and their symbiotic algae. This study has determined that proton pumps in the symbiosome membrane acidify the symbiosome to pH~4 thus promoting CO2 transport, and that this mechanism is essential for oxygen production by the zooxanthellae. This mechanism implies that coral host cells can actively regulate the metabolism of their symbionts, thus setting the stage for further novel research on metabolic and physiological coordination of coral-algae symbiosis and stress responses, for example in relation to bleaching.
(2) Barott KL, Venn A, Perez SO, Tambutteé S, Tresguerres M (in press, PNAS).

3) We are characterizing the localization and function of several ion-transporting proteins and ATPases in various coral species. These proteins are likely involved in delivering inorganic carbon (carbon dioxide, bicarbonate, carbonate) for calcification and photosynthesis. Some preliminary results suggests that two distantly related coral species use different cellular mechanisms, which could help explain differential responses to environmental stress.

4) We also study the bicarbonate-sensing soluble adenylyl cyclase (sAC), which may mediate multiple physiological responses in corals”. We are characterizing its kinetic properties, potential isoforms and splice variants, and cellular localization. sAC may act as regulator of intracellular pH, photosynthesis, gene expression, and gamete physiology in response to metabolic and environmental acid/base conditions.

5) We are interested in coral aerobic and anaerobic metabolic pathways. As corals experience hyperoxic and hypoxic conditions on a daily basis, our prediction is that they must switch from aerobic and anaerobic metabolism. We have already found changes in the phosphoproteome between day and night, and have identified consistent changes in the activity and protein abundance of a few key metabolic enzymes, also on a day/night basis.

6) The ultimate goal is to look at these molecular and cellular mechanisms in corals living in different conditions in the wild, to investigate their relevance in the ‘real world’. Furthermore, since at least some basic molecular and cellular mechanisms are species-specific, we will use compare and contrast several coral species.

See Katie Barott’s, Megan Barron’s, Lauren Linsmayer’s and Sidney Perez’ pages for more details.