The Carbonic Anhydrase Domain of mitochondrial respiratory Complex I is essential to sustain embryogenesis in Arabidopsis thaliana

JUAN PABLO CORDOBA, DEBORA SOTO, VICTORIA MARTIN, GABRIELA PAGNUSSAT, EDUARDO ZABALETA

Mar del Plata

Congreso; XV Congreso Latinoamericano XXX Reunión Argentina de Fisiología Vegetal; 2014

Sociedad Argentina de Fisiología Vegetal

The NADH-ubiquinone oxidoreductase (Complex I -CI-, EC 1.6.5.3) of the mitochondrial respiratory chain contains, in a variety of eukaryotic organisms, an extra domain named Carbonic Anhydrase (CA) domain. It seems to be composed of trimers of gamma carbonic anhydrases and was proposed as an ancestral Complex I assembly factor. However, its physiological role in plants is not fully understood. In Arabidopsis, this protein domain contains a combination of three different CA proteins, named CA1, CA2 and CA3 and two less well conserved CAlike proteins, CAL1 and CAL2, which contain alterations to the primary structure of typical gamma-CAs. In this work we describe a novel double knockout mutant, ca1ca2, which shows lethality during embryogenesis, showing around 24% of delayed white embryos at linear cotyledon stage. The seeds then turn to dark brown at maturity and are smaller than WT ones. This phenotype is similar to the cal1cal2 mutant plants. Additionally, the double ca1ca2 mutant embryos shows ROS accumulation, mitochondrial membrane depolarization and apparently affected oil accumulation. 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.