The contribution of biophysical and biochemical CO concentration mechanisms to the carbon fixation of the green macroalga .

UNLABELLED

CO concentration mechanisms (CCMs) are important in maintaining the high efficiency of photosynthesis of marine algae. Aquatic photoautotrophs have two types of CCMs: biophysical CCMs, based on the conversion of inorganic carbon, and biochemical CCMs, based on the formation of C acid intermediates. However, the contribution of biophysical and biochemical CCMs to algal carbon fixation remains unclear. Here, we used ethoxyzolamide (EZ) inhibitors of carbonic anhydrase and 3-mercaptopicolinic acid (MPA) inhibitors for phosphoenolpyruvate carboxykinase to examine the importance of biophysical and biochemical CCMs in photosynthesis of the green macroalga . The culture experiments showed that the carbon fixation of the species declined when EZ inhibited the biophysical CCM, while the increase in cyclic electron flow around the photosystem I indicated a more active biochemical CCM, contributing to ~ 50% of total carbon fixation. The biophysical CCM was also reinforced when MPA inhibited the biochemical CCM. In a comparison, the biophysical CCM can compensate for almost 100% of total carbon fixation. The results indicate that biophysical CCMs dominate the process of carbon fixation of while biochemical CCM plays a supporting role. Our results provide evidence of a complementary coordination mechanism between the biophysical and biochemical CCMs that promotes the efficiency of photosynthesis of , an efficient mechanism to boost the alga's bloom.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42995-024-00265-7.