Functional and interaction analyses of gamma CA3 protein in Arabidopsis mitochondrial complex I

FASSOLARI MARISOL, SOTO DÉBORA, CORDOBA JUAN PABLO, PAGNUSSAT GABRIELA, ZABALETA EDUARDO

Mar del Plata

Congreso; LI Reunión de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2015

Plant mitochondrial complex I contains an extra domain named Carbonic Anhydrase (CA) domain which is composed by gamma type carbonic anhydrases. This domain was proposed to function in complex I assembly and in photorespiration. In Arabidopsis thaliana there are five of these proteins called CA1, CA2, CA3, CAL1 and CAL2, however only four were found into the CA domain. So far, the exact localization of CA3 subunit remains unknown although is considered a complex I subunit. Here, we show that ca2-ca3 double mutants present a growth retardation phenotype in normal air but are not rescued by cultivating plants at high CO2 atmosphere suggesting strong respiratory rather than photorespiratory phenotype. Moreover, ca1-ca3 double mutants present an embryo lethal phenotype. In order to analyze the interaction between CA and CAL proteins in plant cells and elucidate the CA domain composition, bimolecular fluorescence complementation assays were carried out. Our results show that while CA1 and CA2 proteins are able to interact with CAL proteins, the CA3 protein does not although it is able to form homodimers. Despite we could not find direct interactions between CA3 and bona fide CA domain proteins, our results strongly suggest that CA3 is essential for normal complex I function.