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

Foz de Iguazu

Congreso; 11th International congress of plant molecular biology; 2015

International Society of Plant Molecular Biology

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 armof mitochondrial complex I and its physiological role is currently unknown. None of the T-DNAinsertional single mutants show any visible phenotype under normal conditions. Nevertheless,CA2 was suggested to be essential for complex I assembly since ca2 single mutant show 80%reduction of complex I level. In order to investigate the role of the CA domain, we performedcrosses of single mutants to obtain different double mutants. The ca2cal1 and ca2cal2 mutantsshow a photorespiratory phenotype, showing growth retardation in normal air. This phenotype isrescued by cultivating plants in a high carbon dioxide atmosphere. Moreover, underphotorespiratory conditions, complex I level and carbon assimilation are reduced and glycineaccumulates, which suggests a photorespiratory imbalance. These results strongly suggest thatthe CA domain of plant complex I contributes to sustain an efficient photosynthesis at ambient(photorespiratory) conditions. However, ca2ca3 double mutant is not completely rescued underhigh CO2 suggesting a respiratory failure. Moreover, the ca1ca2 and ca1ca3 double mutantspresent an embryo lethal phenotype due to strong respiratory problems triggering ROSaccumulation. Dry seeds are shrunken and dark brown, however are able to germinate two weekslater than normal. Indeed, double knockout seedlings die most likely due to oxidative stress. Thisphenotype is similar to that observed in cal1cal2 double knockout plants, suggesting it isnecessary at least one CA and one CAL protein to form a functional CA domain.