Arabidopsis SCO proteins oppositely influence cytochrome c oxidase levels and gene expression during salinity stress

MANSILLA N; WELCHEN E; GONZALEZ DH

PLANT AND CELL PHYSIOLOGY

OXFORD UNIV PRESS

Año: 2019

0032-0781

SCO proteins are involved in the insertion of copper during the assembly of cytochromec oxidase (COX), the final enzyme of the mitochondrial respiratory chain. Two SCOproteins, named HCC1 and HCC2, are present in seed plants, but HCC2 lacks theresidues involved in copper binding, leading to uncertainties about its function. In thiswork, we performed a transcriptomic and phenotypic analysis of Arabidopsis thalianaplants with reduced expression of HCC1 or HCC2. We observed that a deficiency inHCC1 causes a decrease in the expression of several stress-responsive genes, both underbasal growth conditions and after applying a short-term high salinity treatment. Inaddition, HCC1 deficient plants show a faster decrease in chlorophyll content,photosystem II quantum efficiency, cyanide-sensitive respiration, and COX activity andlevels after salinity stress. Notably, HCC2 deficiency causes opposite changes in theseparameters. Bimolecular fluorescence complementation analysis indicated that bothproteins are able to interact. We postulate that HCC1 is a limiting factor for COXassembly during high salinity conditions and that HCC2 probably acts as a negativemodulator of HCC1 activity through protein-protein interactions. In addition, a direct orindirect role of HCC1 and HCC2 in the gene expression response to stress is proposed.