Expression of a CO<sub>2</sub>-permeable aquaporin enhances mesophyll conductance in the C<sub>4</sub> species <i>Setaria viridis</i>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34842138.
- Also identified by DOI 10.7554/eLife.70095 and PMC identifier 8648302.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
A fundamental limitation of photosynthetic carbon fixation is the availability of CO<sub>2</sub>. In C<sub>4</sub> plants, primary carboxylation occurs in mesophyll cytosol, and little is known about the role of CO<sub>2</sub> diffusion in facilitating C<sub>4</sub> photosynthesis. We have examined the expression, localization, and functional role of selected plasma membrane intrinsic aquaporins (PIPs) from <i>Setaria italica</i> (foxtail millet) and discovered that SiPIP2;7 is CO<sub>2</sub>-permeable. When ectopically expressed in mesophyll cells of <i>Setaria viridis</i> (green foxtail), SiPIP2;7 was localized to the plasma membrane and caused no marked changes in leaf biochemistry. Gas exchange and C<sup>18</sup>O<sup>16</sup>O discrimination measurements revealed that targeted expression of SiPIP2;7 enhanced the conductance to CO<sub>2</sub> diffusion from the intercellular airspace to the mesophyll cytosol. Our results demonstrate that mesophyll conductance limits C<sub>4</sub> photosynthesis at low <i>p</i>CO<sub>2</sub> and that SiPIP2;7 is a functional CO<sub>2</sub> permeable aquaporin that can improve CO<sub>2</sub> diffusion at the airspace/mesophyll interface and enhance C<sub>4</sub> photosynthesis.
Medical subject headings
- Aquaporins
- Carbon Dioxide
- Photosynthesis
- Setaria Plant