Photorespiration is a biochemical pathway, wherein light-dependent O₂ consumption is coupled with CO₂ release through catabolism of photosynthate at the expense of cellular energy. Therefore, photorespiration is largely viewed as unfavorable to primary productivity and widely considered to be a wasteful process. Algal species especially belonging to cyanobacteria, dinoflagellates and green algae would be CO₂ limited under current levels, with nearly 50% of the carbon and energy being lost to photorespiration. Carbon concentrating mechanism (CCM) helps alleviate this CO₂ limitation by concentrating CO₂ near RUBISCO enzyme, thereby playing a significant role in net CO₂ fixation. However, the processes activating CCM remains a mystery, with certain species repressing their CCM under high CO₂ levels, while some maintain CCM activity. Photorespiration mutants depend on high CO₂ to grow phototrophically, suggesting a link between photorespiration and CCM. Our data shows that metabolic inhibition of photorespiration results in reduced growth amongst species of cyanobacteria, dinoflagellates and green algae, but not diatoms. Furthermore, addition of hydroxypyruvate to photorespiration mutants restarted their growth and phototrophic viability. Further physiological and gene expression studies are underway to decipher the role of the photorespiration pathway in activating CCM and how taxa dependent variation in these processes will affect the phytoplankton community composition in a changing world.

Primary Presenter: Manoj Kamalanathan, Bigelow Laboratory for Ocean Sciences (manojkamalanathan711@gmail.com)

Authors:

Mila Matney, Wellesley College  (mm116@wellesley.edu)

Pete Countway, Bigelow Laboratory for Ocean Sciences  (pcountway@bigelow.org)