New Insights into the physiological role of the Carbonic Anhydrase domain of Arabidopsis Respiratory Complex I

SOTO DEBORA; CORDOBA JUAN PABLO; BARTOLI C; MARCHETTI, MARIA FERNANDA; SCHMITZ J; MAURINO V; BRAUN, H.P; PAGNUSSAT G; EDUARDO JULIAN ZABALETA

Wraslaw

Conferencia; 9th International Conference for Plant Mitochondrial Biology; 2015

Wraslaw University

In Arabidopsis thaliana there are five gamma carbonic anhydrases proteins, called CA1, CA2, CA3, CAL1 and CAL2. These proteins form an extra domain (CA domain) in the membrane arm of mitochondrial complex I and its physiological role is currently unknown. None of the T-DNA insertional single mutants show any visible phenotype under normal conditions. In order to investigate the role of the CA domain, we performed crosses of single mutants to obtain different double mutants. The mutants ca2cal1, ca2cal2 and ca2ca3 show a photorespiratory phenotype, showing growth retardation in normal air. However, this phenotype is rescued by cultivating plants in a high carbon dioxide atmosphere. Moreover, under photorespiratory conditions, carbon assimilation is reduced and glycine accumulates, which suggests a photorespiratory imbalance. ca2ca3 is not completely rescued showing an intermediate phenotype. These results strongly suggest that the CA domain of plant complex I contributes to sustain an efficient photosynthesis at ambient (photorespiratory) conditions. On the other hand, the double mutants ca1ca2 and ca1ca3 present an embryo lethal phenotype due to strong respiratory problems triggering ROS accumulation. Dry seeds are shrunken and dark brown, however are able to germinate two weeks later than normal. Indeed, double knockout seedlings die most likely due to oxidative stress. This phenotype is similar to that observed in cal1cal2 silenced plants, suggesting it is necessary at least one CA and one CAL protein to form a functional CA domain.