Homologs of Sco proteins in plants, functions in COX assembly and stress responses

MANSILLA N,; WELCHEN E,; GONZALEZ, DH.; WELCHEN, E.; ATTALLAH, CV.; COMELLI, RN.; MUFARREGE, EF.

Congreso; 11th International Congress of Plant Molecular Biology; 2015

Mitochondria have a main role in cellular metabolism as energy providers through oxidative phosphorylation. Cytochrome c oxidase (CcO) is the last multi-enzymatic complex of the electron transport chain and it was reported that defects in its assembly or activity severely affect cellular respiration and are lethal for some organisms. Plants are not the exception, and we previously demonstrated that lack of several accessory proteins involved in CcO biogenesis causes embryo lethality. One of these accessory proteins, HCC1, is a homolog of Sco proteins involved in the delivery and insertion of copper into CcO. Another Sco protein, HCC2, is only present in plants and does not have a copper binding domain. To further study the role of HCC1 and HCC2, we analyzed global expression profiles of T-DNA knockout mutants in HCC2 (hcc2) and antisense plants for HCC1 (asHCC1) using RNASeq. Both plant genotypes present opposite transcriptional profiles in numerous genes, especially those related with plant responses to biotic and abiotic stress. While hcc2 plants exhibit higher levels of transcripts related to stress responses, asHCC1 plants show lower levels. In agreement with this, these plants show opposite changes in reactive oxygen species levels and in behavior under several stresses. Reducing HCC1 levels may affect stress responses through changes in mitochondrial function. HCC2, instead, may act as a repressor of stress responses under normal growth conditions.