Biotic Stress/Applied Plant Bio

Abstract

CS-8-2 - Chloroplast carbonic anhydrases function in photosynthesis and plant development

Sunday, July 15
3:38 PM - 3:58 PM

The enzyme carbonic anhydrase (CA) catalyzes the reversible reaction of bicarbonate into carbon dioxide (CO2) and water. In C4 and CAM plants, CA plays a vital role in the CO2 concentration mechanism by generating the bicarbonate used by PEPCase in the first carbon fixation step in the pathways. CA’s role in C3 plants is less understood. Studies in which CA-encoding genes were mutated or silenced yielded plants with only minor growth and developmental phenotypes. As a result, researchers have assigned a myriad of roles for CAs in C3 plants from stomatal conductance, plant defense, seedling lethality, and photosynthesis. In the model plant tobacco (Nicotiana tabacum), the CRISPR/Cas9 system was used to knock out chloroplast CAs to study the effects their absence would have on photosynthesis and development. First, the stroma-localized CAs in tobacco (βCA1 and βCA5) were identified and then CRISPR was used to generate mutated lines: Δβca1, Δβca5, and a double knockout Δβca1/ βca5. The single mutant lines showed no striking phenotypic differences from WT tobacco plants. In contrast, the double mutant transgenic line had major developmental delays in germination and produced small, pale leaves with necrotic spots. This phenotype was observable on sucrose media and only partially rescued at CO2 concentrations greater than 4000ppm. The results suggest that the phenotype is not caused by obstructing photosynthesis, but rather by starving multiple biosynthetic pathways that depend on CAs to carboxylate their substrates. This hypothesis was investigated by exogenously supplying products to specific chloroplast pathways dependent on CA activity.  Complementation tests with constructs that express mutated or re-targeted CAs were performed to find out whether they can rescue the WT phenotype. New knowledge of CA's physiological roles affects potential strategies in engineering biosynthetic pathways into the chloroplast to improve crop yields.


 

Co-Authors

Maureen Hanson – Cornell University

Kevin M. Hines

Ph.D. Candidate
Cornell University

Presentation(s):

Send Email for Kevin Hines


Assets

CS-8-2 - Chloroplast carbonic anhydrases function in photosynthesis and plant development



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Chloroplast carbonic anhydrases function in photosynthesis and plant development