Two HCC genes differentially affect salt stress responses in A. thaliana

MANSILLA N; WELCHEN E; GONZALEZ DH

Congreso; International Conference Plant Mitochondrial Biology (ICPMB); 2017

Cytochrome c oxidase (CcO) is the final complex of the mitochondrial electron transport chain. HCC1 is a plant 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 the copper binding domain. To further study the role of HCC1 and HCC2, we analyzed global expression profiles of Arabidopsis knock-out mutants in HCC2 (hcc2) and antisense plants for HCC1 (asHCC1). Both plant genotypes presented opposite transcriptional profiles in numerous Gene Ontology terms. For instance, hcc2 plants exhibited higher levels of transcripts related to stress responses while asHCC1 plants showed decreased expression of many of these genes. In agreement with this, these plants showed differential responses to NaCl stress: hcc2 plants were more tolerant than control plants and asHCC1 plants were more sensitive. Likewise, transcripts of stress-responsive genes showed earlier or increased induction in asHCC1 plants after long term treatments but the short term response of mitochondrial stress related transcripts was diminished or abolished. An opposite behavior was observed in hcc2 plants. The results suggest that Arabidopsis HCC proteins have developed roles beyond CcO assembly during plant evolution and have opposite roles in the modulation of plant stress responses. Both proteins are able to interact in planta according to bimolecular fluorescence complementation (BiFC) assays. We propose that HCC2, through these interactions, may modulate the redox properties of HCC1 and possibly its function in CcO assembly and/or stress responses.