The induction of pyrenoid synthesis by hyperoxia and its implications for the natural diversity of photosynthetic responses in Chlamydomonas
Peter Neofotis, Joshua Temple, Oliver L Tessmer, Jacob Bibik, Nicole Norris, Eric Pollner, Ben Lucker, Sarathi M Weraduwage, Alecia Withrow, Barbara Sears, Greg Mogos, Melinda Frame, David Hall, Joseph Weissman, David M Kramer
Abstract
In algae, it is well established that the pyrenoid, a component of the carbon-concentrating mechanism (CCM), is essential for efficient photosynthesis at low CO 2 . However, the signal that triggers the formation of the pyrenoid has remained elusive. Here, we show that, in Chlamydomonas reinhardtii , the pyrenoid is strongly induced by hyperoxia, even at high CO 2 or bicarbonate levels. These results suggest that the pyrenoid can be induced by a common product of photosynthesis specific to low CO 2 or hyperoxia. Consistent with this view, the photorespiratory by-product, H 2 O 2 , induced the pyrenoid, suggesting that it acts as a signal. Finally, we show evidence for linkages between genetic variations in hyperoxia tolerance, H 2 O 2 signaling, and pyrenoid morphologies.