The Carbonic Anhydrase Domain of Arabidopsis Respiratory Complex I is essential to sustain embryogenesis

CÓRDOBA, JUAN PABLO; SOTO, DÉBORA; MARTIN, MARÍA VICTORIA; PAGNUSSAT, GABRIELA CAROLINA; ZABALETA, EDUARDO JULIÁN

Rosario

Conferencia; 8th International Conference for Plant Mitochondrial Biology; 2013

Plant Mitochondrial Biology

The NADH-ubiquinone oxidoreductase (Complex I -CI-, EC 1.6.5.3) of the mitochondrial respiratory chain is the principal entrance of electrons from metabolism and redox balance. Additionally, in a variety of eukaryotic organisms, except animal and fungi (Opisthokonta), it contains an extra domain composed of trimers of putative gamma carbonic anhydrases, named CA domain, proposed as an ancestral assembly factor. However, its physiological role in plants is not fully understood. In Arabidopsis, this protein domain contains at least two different CA proteins, named CA1 and CA2 showing conserved active site regions and two less well conserved CAlike proteins, CAL1 and CAL2, which contain alterations to the primary structure of typical gamma-CAs. According to the proposed structure of complex I, a third CA (CA3) appears to be outside the CA domain. In this report, we describe a novel double knockout mutant, ca1ca2, which shows lethality during embryogenesis, having around 21% of arrested white embryos from heart to torpedo stages. These arrested embryos turn to dark brown at maturity. This phenotype is similar to the cal1cal2 double mutants. Since single mutants show wild type phenotypes indicating protein redundancy, these results reveal that at least one CA and one CAL protein is required to form an active CA domain essential to sustain embryogenesis.