Absence of carbonic anhydrase in chloroplasts affects C <sub>3</sub> plant development but not photosynthesis
Kevin M. Hines, Vishalsingh Chaudhari, Kristen N. Edgeworth, Thomas G. Owens, Maureen R. Hanson
Abstract
Significance Carbonic anhydrase enzymes located in chloroplast stroma have been hypothesized to facilitate photosynthesis in C 3 plants because they catalyze a reaction involving bicarbonate and CO 2 , a substrate of the carbon-fixing enzyme RuBisCO. To test this possibility, tobacco mutants completely lacking chloroplast stromal carbonic anhydrase activity were produced by CRISPR/Cas9 mutagenesis. The plants displayed normal photosystem II activity and CO 2 assimilation but also abnormal development and increased reactive oxygen species and stromal pH. We conclude that chloroplast carbonic anhydrase does not play a direct role in providing CO 2 for carbon fixation. Instead, as is also true in microorganisms, carbonic anhydrase is necessary to supply bicarbonate for biosynthetic processes.