Characterization of photosynthetic protein complexes in conchocelis and blades of Pyropia yezoensis (Rhodophyta)

The red alga Pyropia yezoensis is an economically important marine crop whose life cycle includes two distinct stages: conchocelis and blades. These two types of thalli live in significantly different environments and have distinct shapes and physiological features. The photosynthetic apparatus of red algae, especially the light harvesting antenna, is unique. However, little is known about the photosynthetic apparatus of P. yezoensis. We studied the composition and organization of thylakoid membranes in conchocelis and blades of P. yezoensis and found that the photosynthetic complexes differed between the two stages. Conchocelis had much higher photosystem I (PSI)/ photosystem II and PSI/Cytochrome b6/f ratios compared with blades. Additionally, a macromolecular protein complex that bound with lutein and Chlorophyll a was detected in conchocelis but not in blades. The number and types of light harvesting complex subunits associated with PSI and the corresponding pigment binding also varied between conchocelis and blades. These differences are an important strategy that allows the two P. yezoensis stages to adapt to various environments.