Role of C4 carbon fixation in Ulva prolifera, the macroalga responsible for the world’s largest green tides

• Published in: Communications biology Vol. 3; no. 1; p. 494
• Main Authors: Liu, Dongyan, Ma, Qian, Valiela, Ivan, Anderson, Donald M., Keesing, John K., Gao, Kunshan, Zhen, Yu, Sun, Xiyan, Wang, Yujue
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.09.2020; Nature Publishing Group
• Subjects: 631/158/1745; 631/449/1734; 631/449/2668; 631/449/2686; Algae; Biology; Biomedical and Life Sciences; Carbon; Carbon dioxide; Carbon fixation; Carbonic anhydrases; Dehydration; Life Sciences; Photosynthesis; Seaweeds; Species; Ulva prolifera
• ISSN: 2399-3642; 2399-3642
• DOI: 10.1038/s42003-020-01225-4

Most marine algae preferentially assimilate CO 2 via the Calvin-Benson Cycle (C 3 ) and catalyze HCO 3 − dehydration via carbonic anhydrase (CA) as a CO 2 -compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C 4 ) to enhance photosynthesis. The occurrence and importance of the C 4 pathway remains uncertain, however. Here, we demonstrate that carbon fixation in Ulva prolifera , a species responsible for massive green tides, involves a combination of C 3 and C 4 pathways , and a CA-supported HCO 3 − mechanism. Analysis of CA and key C 3 and C 4 enzymes, and subsequent analysis of δ 13 C photosynthetic products showed that the species assimilates CO 2 predominately via the C 3 pathway, uses HCO 3 − via the CA mechanism at low CO 2 levels, and takes advantage of high irradiance using the C 4 pathway. This active and multi-faceted carbon acquisition strategy is advantageous for the formation of massive blooms, as thick floating mats are subject to intense surface irradiance and CO 2 limitation. Liu et al. present evidence that carbon fixation in Ulva prolifera takes place via a combination of C 3 and C 4 pathways in combination with the enzyme carbonic anhydrase. The active and multi-faceted carbon acquisition strategy in U. prolifera is advantageous for the formation of massive blooms as the thick floating mats are subject to intense surface irradiance and CO 2 limitation.