AtSIA1 AND AtOSA1: two Abc1 proteins involved in oxidative stress responses and iron distribution within chloroplasts



  • The Abc1 protein kinases are a large family of functionally diverse proteins with multiple roles in the regulation of respiration and oxidative stress tolerance.
  • A functional characterization was carried out for AtSIA1, an Arabidopsis thaliana Abc1-like protein, focusing on its potential redundancy with its homolog AtOSA1. Both proteins are located within chloroplasts, even if a different subplastidial localization seems probable. The comparison of atsia1 and atosa1 mutants, atsia1/atosa1 double mutant and wild-type plants revealed a reduction in plastidial iron-containing proteins of the Cytb6f complex in the mutants. Iron uptake from soil is not hampered in mutant lines, suggesting that AtSIA1 and AtOSA1 affect iron distribution within the chloroplast.
  • Mutants accumulated more ferritin and superoxide, and showed reduced tolerance to reactive oxygen species (ROS), potentially indicating a basal role in oxidative stress. The mutants produced higher concentrations of plastochromanol and plastoquinones than wild-type plants, but only atsia1 plants developed larger plastoglobules and contained higher concentrations of α- and γ-tocopherol and VTE1.
  • Taken together, these data suggest that AtSIA1 and AtOSA1 probably act in signaling pathways that influence responses to ROS production and oxidative stress.