Cyclic AMP levels in several macroalgae and their relation to light quantity and quality

Area of Science:

• Marine Botany
• Phycology
• Plant Physiology

Background:

• Cyclic adenosine monophosphate (cAMP) is a crucial second messenger in eukaryotic cells.
• The regulation of cAMP levels in macroalgae under varying light conditions remains incompletely understood.
• Phytochrome and photosynthesis are potential regulators of cellular processes in algae.

Purpose of the Study:

• To investigate the role of phytochrome versus photosynthesis in regulating total cAMP levels in macroalgae.
• To determine the influence of different light conditions on cAMP accumulation in Dictyota dichotoma, Gelidium sesquipedale, and Ulva rigida.

Main Methods:

• Measurement of total cAMP levels in three macroalgae species (D. dichotoma, G. sesquipedale, U. rigida).
• Exposure to different light conditions, including red, far-red, and white light at sub-saturating irradiance.
• Assessment of the effects of inhibitors targeting thylakoidal and mitochondrial electron transport chains.

Main Results:

• Red or far-red light did not induce a phytochrome-like response but synergistically increased cAMP accumulation.
• cAMP levels correlated with applied light energy and photosynthetic oxygen evolution, particularly in G. sesquipedale and U. rigida.
• Inhibitors of electron transport chains drastically reduced cAMP levels (70-99%), implicating photosynthetic and mitochondrial activity.

Conclusions:

• Photosynthetic activity, rather than phytochrome, appears to be the primary regulator of cAMP accumulation in the studied macroalgae.
• The energy generated through photosynthetic electron transport is directly linked to cAMP regulation.
• These findings highlight the significant role of photosynthesis in intracellular signaling pathways of marine macroalgae.